Ebook Diagnostic imaging gastrointestinal: Part 2

(BQ) Part 2 book Diagnostic imaging gastrointestinal presents the following contents: Spleen (normal variants and artifacts, congenital, congenital,...), liver (congenital, infection, metabolic or inherited,...), biliary system (normal variants and artifacts, congenital, vascular disorders,...), pancreas (degenerative, treatment related, malignant neoplasms,...).

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SECTION 8 Spleen

Introduction and Overview

Normal Variants and Artifacts

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Imaging Approach to the Spleen

Embryology, Anatomy, and Physiology

The spleen develops from the dorsal mesogastrium and

usually rotates to the left, becoming fixed in the left

subphrenic location by peritoneal reflections linking it to the

diaphragm, abdominal wall, stomach (gastrosplenic ligament),

and kidney (splenorenal ligament) It usually develops as 1

"fused" mass of tissue, but variations are common

One or more accessory spleens are found in up to 30% of the

general population, usually small spherical structures near the

splenic hilum These can enlarge, especially following

splenectomy, and may simulate a neoplastic mass or cause

recurrence of hematologic disease

The spleen may be congenitally absent (asplenia) or have

many unfused components (polysplenia) These are rare

splenic anomalies and are associated with cardiovascular

anomalies, situs inversus, and other anomalies, often with

serious and even life-threatening consequences

The spleen is rarely on a long mesentery and may be found in

any abdominal or pelvic location ("wandering spleen"), placing

it at risk for trauma and torsion with infarction

The spleen is the largest lymphatic organ, the size of which

varies among individuals and even in the same person by

blood volume, state of nutrition and hydration The usual

volume range is 100-250 cm³, with a mean of 150 cm³ A

calculated splenic index (length x width x breadth) over 480

cm³ is considered splenomegaly The average length is up to

12 cm, with a width and breadth of 7 and 4 cm, respectively

Imaging Issues

The spleen has a unique histology, consisting of the red and

white pulp, which directly affects its appearance on imaging

exams The white pulp is the lymphoid tissue and the red is

composed of the vascular tissue and splenic cords (plates of

cells and sinusoids) Because of its vascularity, the red pulp

enhances rapidly, giving the spleen a very heterogeneous

pattern of enhancement on arterial phase enhanced CT or MR

imaging This may be mistaken for splenic pathology but is a

transient phenomenon not evident on unenhanced or later

phases of enhanced imaging

CT is the imaging modality of choice for the evaluation of the

spleen in the acute setting (trauma or pain) MR can be

additive in evaluating splenic masses and some metabolic

diseases (e.g., hemochromatosis) The spleen has a relatively

long T1 and T2 relaxation time This results in its appearing

somewhat hypointense compared to the liver on T1WI and

hyperintense on T2WI With iron deposition, the spleen may

show a dramatic loss in signal

Approach to the Abnormal Spleen

Splenomegaly is a very common finding and may result from

numerous causes, usually grouped into 5 general etiologies,

including congestion, hematologic, inflammatory-infectious ,

tumor, or infiltrative

Given its function as a blood filter, it is not surprising that the

spleen is a frequent site of metastases on postmortem

examination of patients who have died from cancer However,

with the exception of leukemia and lymphoma, it is

uncommon to make an imaging diagnosis of splenic

metastasis

Many splenic neoplasms are benign, either hemangiomas orlymphangiomas, but these have overlapping imaging featuresand a specific diagnosis is rarely possible

One of the most common focal splenic lesions is the spleniccyst It is not possible to distinguish the primary congenital(epithelial-lined) cyst from the acquired cyst by imaging, withthe latter resulting from prior infarction, infection, or trauma.These are rarely of clinical importance

Multiple lesions within the spleen are most typically the result

of a granulomatous process, which may be either infectious(e.g., histoplasmosis, TB) or noninfectious (sarcoidosis) Splenicgranulomata commonly calcify

The pancreatic tail usually inserts into the splenic hilumthrough the splenorenal ligament Inflammatory or neoplasticconditions affecting the pancreatic tail can easily invade thesplenic parenchyma, resulting in intrasplenic pseudocyst, forinstance Conversely, splenic tumors or an accessory spleenmay mimic a pancreatic tail mass

Splenic infarction is a relatively common cause of acute leftupper quadrant pain It appears as a sharply defined, oftenwedge-shaped zone of minimal enhancement abutting thesplenic capsule Patients at risk for infarction include thosewith sickle cell disease and those with cardiovascularconditions, such as atrial fibrillation Patients with leftventricular assist devices are especially prone to embolicinfarction of the spleen

The spleen is often injured in blunt and penetrating trauma.Most children and adults with splenic lacerations will recoverwithout surgery, but the presence of active extravasation(evident on CT) or clinical instability may demand intervention,either surgery or transcatheter embolization

Splenosis is the peritoneal implantation of splenic tissue thatmay follow traumatic rupture of the spleen This may bemistaken for polysplenia or peritoneal implants of tumor(carcinomatosis) The history of trauma, absence of a normalspleen, and enhancement characteristics identical to spleenusually allow accurate diagnosis

Differential DiagnosisSplenomegaly

Common

• Cirrhosis with portal hypertension

• Congestive heart failure

• Splenic tumors (primary)

• Systemic infection and abscesses

• Splenic vein occlusion

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Multiple Splenic Calcifications

• Acquired or congenital splenic cyst

• Splenic trauma

• Splenic infarctionLess common

• Splenic metastases and lymphoma

• Splenic infection and abscess

• Splenic tumors

• Pancreatic pseudocystDiffuse Increased Attenuation, SpleenCommon

(Left) Arterial phase axial

CECT shows a very heterogeneous spleen caused

by rapid enhancement of the vascular sinusoids (red pulp).

This should not be mistaken for a pathologic process.

(Right) Axial CECT during the

venous phase shows the spleen with a homogeneous appearance.

(Left) Axial T1WI MR (A) shows

the normal spleen ﬅ as slightly hypointense relative to liver On T2WI MR (B), the normal spleen is slightly hyperintense to liver.(Right)

Axial CECT shows a "mass" ﬅ

in the pancreatic tail that is isodense to the spleen and represents an accessory spleen This could be mistaken for a primary pancreatic mass, such as a neuroendocrine tumor.

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Splenocolic ligament

(Top) Graphic shows the medial surface of the spleen and representative axial sections at 3 different levels The spleen is of variable

shape and size, even within the same individual, varying with states of nutrition and hydration The medial surface is often quite lobulated as it is interposed between the stomach and the kidney (Bottom) The splenic artery and vein course along the body of the

pancreas, entering and exiting the spleen via the splenorenal ligament The tail of the pancreas also inserts into the splenic hilum through the splenorenal ligament The gastrosplenic ligament carries the short gastric and left gastroepiploic vessels to the stomach and upper portion of the spleen.

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(Left) Axial CECT in a patient

with non-Hodgkin lymphoma shows numerous enlarged upper abdominal lymph nodes

ﬅ Splenomegaly is a common abnormality and can

be caused by congestion, hematologic disorders, inflammatory/infectious conditions, tumors, or infiltrative processes.(Right)

Axial CECT in a different case

of splenomegaly caused by congestion secondary to cirrhosis and portal hypertension shows the recanalized umbilical vein ﬅ.

(Left) Axial CECT shows 2

splenic lesions The larger lesion ﬈ has water density contents and thin, sharp walls, typical of simple cyst The smaller lesion ﬊ has nodular walls and higher density contents, suggestive of splenic lymphangioma (Right) In this

patient with non-Hodgkin lymphoma the spleen is markedly enlarged with heterogeneous, hypoattenuating, more discrete tumor foci ﬈.

Lymphomatous infiltration is also present within the adrenal gland ﬉ and nodes

﬇ throughout the abdomen.

with heart failure and abdominal pain shows a ventricular assist device ﬆ and wedge-shaped regions of nonenhancing splenic parenchyma ﬅ that extend to the capsular surface,

characteristic of acute splenic infarctions (Right) Axial CECT

in a patient injured in a motor vehicle crash shows a sentinel clot ﬆ adjacent to the spleen and a large hemoperitoneum

﬇ Note the active extravasation of blood ﬅ that

is isodense to enhanced vessels.

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• Most splenules located in or near splenic hilum or ligaments

○ 20% are near or within pancreatic tail and can mimicpancreatic neuroendocrine tumor

○ May also be in diaphragmatic, pararenal, and gastric sites

• NECT and CECT: Same enhancement and attenuation as

normal spleen

○ Isodense to main spleen on noncontrast images

○ Characteristic serpiginous enhancement on arterialphase

○ Homogeneous enhancement on venous/delayed images

• MR: T1WI hypointense and T2WI hyperintense

○ Follows appearance of spleen on all sequences

○ DWI: Isointense to spleen with similar ADC values

• Nuclear medicine: Technetium (99m) sulfur colloid or

Tc-99m heat-damaged red blood cell (RBC) scan

○ Functional uptake in splenic tissue differentiatessplenule from other masses

• Rare complication: Torsion of splenule as cause ofabdominal pain in children or young adults

TOP DIFFERENTIAL DIAGNOSES

• Splenosis

• Polysplenia

• Peritoneal metastases and lymphoma

• Visceral mass (especially pancreatic neuroendocrine tumor)

• Splenic artery aneurysm or pseudoaneurysm

PATHOLOGY

• Congenital: Failure of some embryonic splenic buds to unitewithin dorsal mesogastrium

CLINICAL ISSUES

• Asymptomatic (vast majority of cases)

• In absence of complications (which are extraordinarily rare),

no treatment or intervention

(Left) Axial CECT shows a

small spherical accessory

spleen ﬅ near the splenic

hilum Note the foci of

calcification from

histoplasmosis in the main and

accessory spleen This

appearance is so characteristic

as to require no additional

evaluation (Right) Axial CECT

demonstrates a large mass ﬅ

abutting the pancreatic tail

and the splenic hilum The

mass was thought to be a

neuroendocrine tumor and

was resected Note that the

mass is isodense to the spleen.

The mass was found to be a

splenule at surgery.

(Left) Axial CECT shows an

enlarged spleen due to portal

hypertension in this patient

with cirrhosis Note the

prominent accessory spleen ﬅ

as well as the varices ﬇ An

accessory spleen may enlarge

in parallel with the main

spleen (Right) Axial CECT

shows a hypervascular mass

ﬅ within the pancreatic tail

that mimics an islet cell tumor.

A heat-damaged red blood cell

scan (not shown) proved this

to be an accessory spleen.

Masses in the splenic hilum

may arise from or involve the

tail of the pancreas or spleen.

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• Best diagnostic clue

○ Small, round, well-marginated nodule in left upper

quadrant with same enhancement as normal spleen

• Location

○ In or near splenic hilum or ligaments (most cases)

– 20% are near or within pancreatic tail

– Usually left upper quadrant, above renal pedicle

– Rarely in diaphragmatic, pararenal, and gastric sites

○ Single splenule in vast majority of patients

– 1 splenule (88%), 2 splenules (9%), > 2 splenules (3%)

– Multiple splenules usually clustered in 1 location

• Size

○ Varies from 1 mm to a few cm, usually < 2.5 cm

CT Findings

• Same enhancement as normal spleen

○ Isodense to main spleen on noncontrast images

○ Serpiginous enhancement on arterial phase

○ Homogeneous enhancement on venous/delayed images

• Most commonly located near splenic hilum or ligaments

• 2nd most common location is pancreatic tail

○ Usually < 3 cm medial to pancreatic tail

○ Most often along dorsal surface of pancreas

○ Incompletely surrounded by pancreatic parenchyma

• Rare: Torsion of splenule as cause of abdominal pain

○ Nonenhancing mass with surrounding hemorrhage

○ Whorl sign (twisted vascular pedicle) leading to splenule

MR Findings

• T1WI hypointense and T2WI hyperintense

○ Follows appearance of spleen on all sequences

• DWI: Isointense to spleen with similar apparent diffusion

coefficient (ADC) values

○ Pancreatic neuroendocrine tumors usually hyperintense

on DWI with lower ADC values

• Superparamagnetic iron oxide particles (SPIO) contrast

media taken up by splenic tissue (but not tumor)

Nuclear Medicine Findings

• Technetium (Tc-99m) sulfur colloid or Tc-99m

heat-damaged red blood cell (RBC) scan

○ Functional uptake in splenic tissue differentiates

splenule from other masses

○ Tc-99m heat-damaged RBC scan preferred due to higher

specificity and better target to background

• PET CT

○ FDG-avid mass can mimic tumor

Imaging Recommendations

• Best imaging tool

○ Multiphase CT followed by Tc-99m heat-damaged RBCscan in equivocal cases

Peritoneal Metastases and Lymphoma

• e.g., omental or peritoneal metastases

Visceral Mass

• Splenules commonly mistaken for pancreaticneuroendocrine tumors

• Splenules also mistaken for adrenal, gastric, or renal tumors

Splenic Artery Aneurysm or Pseudoaneurysm

• Bright homogeneous enhancement on arterial phasePATHOLOGY

General Features

• Etiology

○ Congenital: Failure of some embryonic splenic buds tounite within dorsal mesogastrium

Gross Pathologic & Surgical Features

• Structurally normal splenic tissueCLINICAL ISSUES

Presentation

• Most common signs/symptoms

○ Asymptomatic (vast majority of cases)

• Other signs/symptoms

○ May torse, rupture, and bleed (very rare)

○ May cause recurrence of hematologic disease (e.g.,lymphoma) following prior splenectomy

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Asplenia and Polysplenia

KEY FACTS

TERMINOLOGY

• Complex inherited syndromes associated with absence or

multiplicity of spleens as well as many other anomalies

IMAGING

• Asplenia (ASP) syndrome: Right isomerism or bilateral

right-sidedness

○ Absent spleen in virtually all patients

○ Congenital heart disease in ~ 100% of patients

○ Bilateral trilobed lungs

○ Malrotation in most patients

○ Aorta and inferior vena cava (IVC) are frequentlyipsilateral (usually right side)

• Polysplenia (PSP) syndrome: Left isomerism or bilateral

○ IVC interruption with azygos continuation very common

○ Bilateral bilobed lungs

○ Truncated/short pancreas or agenesis of dorsal pancreas– Increased incidence of diabetes and pancreatitis

○ Intestinal malrotation is seen in most patients

○ Liver often midline with range of biliary abnormalities

○ Aorta usually located to left of midline

○ ↑ risk of sepsis due to lack of spleen

• PSP: Infant or adult presentation with better prognosis due

to lesser incidence of cardiac disease

(Left) Coronal

volume-rendered CECT in a patient

with polysplenia (PSP)

syndrome demonstrates

multiple spleens ﬆ in the left

upper quadrant The multiple

spleens in PSP are typically in

the left abdomen, but can

rarely be on the right.(Right)

Axial CECT in the same patient

demonstrates a markedly

dilated azygous vein ﬇.

(Left) Axial CECT in the same

patient again demonstrates

multiple spleens ﬆ and a

dilated azygous vein ﬅ to the

right of the aorta Azygous

continuation of the inferior

vena cava (IVC) is a very

common abnormality in PSP

syndrome (Right) Axial CECT

in the same patient

demonstrates malrotation of

the bowel, with the small

bowel abnormally located in

the right abdomen and the

entirety of the colon in the left

abdomen Malrotation is quite

common with both asplenia

(ASP) and PSP syndromes.

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• Complex inherited syndromes associated with absence

(ASP) or multiplicity (PSP) of spleens, as well as many other

anomalies

Associated Syndromes

• Heterotaxy: Abnormal embryologic placement of

thoracoabdominal structures across right-left axis of body

• Situs solitus: Normal placement of thoracoabdominal

organs in right-left axis

• Situs inversus: Reversal of normal positions of

thoracoabdominal organs across right-left axis

(mirror-image of situs solitus)

• Situs ambiguus (heterotaxy syndrome): Abnormal

placement of thoracoabdominal structures without situs

inversus

IMAGING

General Features

○ ASP: Absence of spleen, abdominal aorta and inferior

vena cava (IVC) on same side (usually right), and bilateral

distribution of right-sided viscera

○ PSP: Multiple small spleens, intrahepatic interruption of

IVC with continuation of azygos vein, bilateral

distribution of left-sided viscera

– Situs ambiguus and bilateral right-sidedness; no fixed

set of findings, abnormalities exist across a spectrum

– Spleen

□ Absent spleen in virtually all patients

– Cardiovascular

□ Congenital heart disease in ~ 100% of patients

□ Total anomalous pulmonary venous return (almost

100%), endocardial cushion defect (85%), single

ventricle (51%), transposition of great vessels

(58%), pulmonary stenosis or atresia (70%),

dextrocardia (42%), mesocardia, ventricular septal

defect, single atrioventricular valve, bilateral

superior vena cava (SVC)

□ Aorta and IVC are frequently ipsilateral (usually

□ Malrotation in most patients with ASP

□ Other associations: Imperforate anus, ectopic liver,annular pancreas, esophageal varices, gallbladderagenesis, Hirschsprung disease, and duplication orhypoplasia of stomach

– Genitourinary

□ Horseshoe kidney, bilobed urinary bladder,hydroureter, double collecting system, cystic kidney– Miscellaneous

□ Cleft palate, cleft lip, fused or horseshoe adrenalgland, absent left adrenal gland, scoliosis,bicornuate uterus, single umbilical artery, lumbarmyelomeningocele

○ PSP syndrome: Left isomerism or bilateral left-sidedness– Situs ambiguus and bilateral left-sidedness: No fixedset of findings and abnormalities exist across aspectrum

□ Transposition of great vessels (13%), double outletright ventricle (13%), pulmonary valvular stenosis(23%), subaortic stenosis, or atresia

□ IVC interruption with azygos vein continuation is2nd most common abnormality (65%) aftermultiple spleens

□ Aorta usually located to left of midline– Pulmonary

□ Abnormal distribution of lobes with bilateralbilobed lungs

□ Only seen in 55% of patients– Gastrointestinal

□ Truncated/short pancreas or agenesis of dorsalpancreas with increased incidence of diabetes andpancreatitis

□ Intestinal malrotation seen in most patients withPSP and may range from nonrotation to completemalrotation

□ Liver often midline with range of biliary treeabnormalities (absent gallbladder, biliary atresia)

□ Isolated reversal of stomach position common

□ Other associations: Esophageal or duodenal atresia,tracheoesophageal fistula, semiannular pancreas,gastric duplication, short bowel

be seen bilaterally– Superior mediastinal widening (due to bilateral SVC)

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– Both pulmonary arteries anterior to trachea on lateralchest film

○ PSP– Frontal view: Paratracheal soft tissue prominence(dilated azygos/hemiazygos) mimicking mass– Chest lateral view: Both pulmonary arteries posterior

to trachea and absence of IVC shadow

○ CECT or MR can demonstrate position and number ofspleen(s), as well as other visceral organ abnormalitiesassociated with heterotaxy syndromes

DIFFERENTIAL DIAGNOSIS

Splenosis

• Scattered splenic tissue throughout abdomen usually seen

in setting of traumatic splenectomy

• Multiple small implants ranging in size from few mm to few

cm; should enhance similarly to normal splenic tissue

• No other associated anomalies

Accessory Spleen

• Normal embryologic variant usually found near splenic

hilum along course of splenic vessels

• Identical to normal splenic tissue on any phase of

enhancement

Splenectomy

• No splenic visualization after surgical splenectomy

PATHOLOGY

General Features

• Etiology

○ Uncertain etiology, but may be associated with gene

mutations (CFC1 gene, SHROOM3 gene, etc.)

– Altered timing in development of embryonic bodycurvature leads to visceroatrial situs abnormalities

□ ASP: Delayed embryonic body curvature

□ PSP: Accelerated embryonic body curvature– Pressure of adjacent structures may interfere withsplenic blood supply leading to development of

CLINICAL ISSUES

Presentation

○ ASP– Most commonly present with cardiopulmonarydisease (83%), including cyanosis as neonates or ininfancy

– Patients are prone to overwhelming sepsis (especiallypostoperatively) due to lack of spleen

– Bowel obstruction (17%) due to malrotation

○ PSP– 10-15% may not present clinically until adulthood– Often present with cardiac disease, including heartmurmur, congestive heart failure, occasional cyanosis,heart block

– Jaundice due to biliary atresia or other biliaryabnormalities

– Abdominal pain related to bowel obstruction orintestinal ischemia related to malrotation

Natural History & Prognosis

• ASP: Very poor prognosis

○ Mortality rate: Prognosis depends on extent of cardiacabnormalities, but only 20% survive to age of 16

• Polysplenia: Fair prognosis, better than asplenia

○ Mortality rate: 50-60% mortality in 1st year, 25% ofpatients live up to 5 years, and 10% survive to midadolescence

Treatment

• ASP: Prophylactic antibiotics (not needed in PSP)

• Surgical correction of cardiac disease or malrotation ineither ASP or PSP

DIAGNOSTIC CHECKLIST

Image Interpretation Pearls

• Left liver lobe can simulate spleen on US leading to misseddiagnosis of ASP

• Differentiate PSP from accessory spleens and splenosisSELECTED REFERENCES

1 Tawfik AM et al: Polysplenia syndrome: a review of the relationship with viscero-atrial situs and the spectrum of extra-cardiac anomalies Surg Radiol Anat 35(8):647-53, 2013

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with PSP syndrome demonstrates multiple spleens

ﬆ located in the right upper quadrant and situs inversus.

Note the reversed positions of the liver and stomach.(Right)

Axial CECT in the same patient demonstrates an abnormal right-sided stomach ﬆ Note that the IVC ﬇ is normally located on the right The majority of the small bowel is

on one side of the abdomen, in keeping with malrotation.

with PSP syndrome shows dextrocardia and a left-sided IVC ﬆ (Right) Axial CECT in

the same patient shows complete abdominal situs inversus with an otherwise normal-appearing stomach ﬅ and liver on the right-hand side Note the left-sided IVC

﬉.

(Left) Axial CECT in the same

patient shows multiple splenules ﬅ in the right upper quadrant along with

abdominal situs inversus.

(Right) Axial CECT in the same

patient shows multiple spleens

ﬅ, situs inversus, and cystic disease of the kidneys ﬇ This patient was 35 years old (patients with PSP are much more likely to reach adulthood than ASP).

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Splenic Infection and Abscess

KEY FACTS

IMAGING

• Pyogenic abscess on CECT

○ Low-attenuation complex fluid collection ± air-fluid levels

○ Internal gas bubbles, which although uncommon, arevery specific for splenic abscess

○ Multiloculated appearance seen with liver abscessespossible, but less common with splenic abscess

○ May extend to subcapsular location and may rarely causesplenic rupture with generalized peritonitis

• Fungal microabscesses on CECT

○ Multiple small hypodense lesions measuring a few mm

○ Multiple punctate splenic calcifications after treatment

• Echinococcal (hydatid) cyst on CECT

○ Complex cyst with multiple low density "daughter" cystsand thick, enhancing wall ("cyst within a cyst")

○ Serpiginous, linear densities within cyst due to collapsedparasitic membranes (water lily sign)

○ May demonstrate thick peripheral calcification orinternal wavy, curvilinear calcification in chronic setting

• Multiple different causes for splenic pyogenic abscesses

○ Generalized septicemia, septic emboli (usually in setting

of endocarditis with mitral &/or aortic valve vegetations),

or secondary infection of traumatic splenic hematoma orinfarct

• Most fungal microabscesses occur in setting ofimmunosuppression, HIV/AIDS, or hematologic disorders

• Echinococcal infections occur due to infection with

tapeworm (Echinococcus granulosus)

multiloculated mass ﬆ within

the spleen that proved to be a

pyogenic abscess Such large

abscesses are unusual in the

spleen, especially in the

absence of prior splenic

infarction (Right) Axial CECT

in a patient with a recent

history of traumatic injury to

the spleen and a new fever ﬅ

demonstrates a rim-enhancing

fluid collection with an

air-fluid level ﬆ, consistent with

a splenic abscess The patient

was treated with

percutaneous drainage and

antibiotics.

with HIV/AIDS who was

admitted with fever and

weight loss demonstrates

microabscesses ﬆ throughout

the spleen The patient

deteriorated rapidly, and

multiple tuberculous

abscesses were identified at

autopsy (Right) Axial CECT

shows a splenic hydatid cyst

ﬅ with additional similar

lesions in the liver and

peritoneal cavity ﬆ, many of

which have calcified walls.

This patient had a prior

rupture of a hepatic hydatid

cyst with diffuse spread

throughout the abdomen.

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○ Rounded low-attenuation complex fluid collection with

○ Variable: Typically 3-5 cm for pyogenic abscesses; < 1.5

cm for microabscesses (often fungal)

• Morphology

○ Rounded cystic mass with irregular borders

– May have multiple locules similar to cluster sign of

hepatic pyogenic abscess

– Internal septations common

– Exerts mass effect on splenic capsule

Radiographic Findings

• Radiography

○ Very rarely gas bubbles within abscess may be visualized

on radiographs

○ Often associated with left lower lobe atelectasis and left

pleural effusion on chest radiograph

CT Findings

• Pyogenic abscess

○ Low-attenuation (20-40 HU) complex fluid collection ±

air-fluid levels

– May have an enhancing peripheral rim, but not as

conspicuous as generally seen with liver abscesses

– May have internal gas bubbles, which although

uncommon, are very specific for splenic abscess

– May have multiloculated appearance seen with liver

abscesses, but less common with splenic abscess

○ May extend to subcapsular location and may rarely cause

splenic rupture with generalized peritonitis

• Fungal microabscesses

○ Often multiple, small, hypodense lesions measuring just

a few mm

○ Can be very difficult to diagnose on NECT

○ May manifest as multiple punctate splenic calcifications

after treatment

• Echinococcal (hydatid) cyst

○ Complex cyst with multiple low density "daughter" cysts

and thick, enhancing wall composed of fibrous tissue

("cyst within a cyst" appearance)

○ Serpiginous, linear hypodense bands within cyst due to

collapsed parasitic membranes (water lily sign)

○ May demonstrate thick peripheral calcification or

internal wavy, curvilinear calcification in chronic setting

○ Similar lesions may be seen in liver or peritoneum

MR Findings

• Fluid signal at center of lesion (hyperintense on T2WI andhypointense on T1WI) with peripheral enhancement onT1WI C+ images

• Old healed/treated fungal microabscesses may showblooming artifact on GRE sequences due to calcification

Ultrasonographic Findings

• Grayscale ultrasound

○ Pyogenic abscess– Hypoechoic or anechoic mass with internal septationsand low-level echoes representing pus or debris

□ Rarely, atypical splenic abscess appears echogenic– May have variable degrees of posterior acousticenhancement, depending on cyst contents– "Dirty" shadowing and ring-down artifact suggestpresence of gas within collection

□ US is much less sensitive for ectopic gas than CT

○ Fungal microabscesses– "Target" or bull's-eye appearance similar to hepaticmicroabscesses

• May be single or multiple discrete masses

• Most common solid malignancies include lymphoma,melanoma, and other metastases

○ Melanoma and some cystic/necrotic metastases (ovariancancer, sarcomas, germ cell tumors) can appear lowdensity and cystic, mimicking abscess or fluid collection

○ Lymphoma can present with innumerable tinyhypodense nodules in spleen mimicking microabscesses

• Most common benign lesions are lymphangioma andhemangioma

○ Variable appearance; both lesions can appear low densityand mimic abscess or fluid collection

○ Hemangioma may appear hypervascular on arterialphase CECT and lymphangioma may show internalloculations and septations

Splenic Trauma

• History of recent blunt injury

• Linear low density, nonenhancing laceration almost alwaysassociated with perisplenic hematoma and

hemoperitoneum

• ± active arterial extravasation

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Infiltrating Disorders

• Sarcoid (and less commonly, Gaucher disease) can

commonly present with multiple low-attenuation lesions

• Indistinguishable from microabscesses without history

• Sarcoid may be associated with similar lesions in liver,

hepatosplenomegaly, and thoracic/upper abdominallymphadenopathy

– Septic emboli (usually in setting of endocarditis withmitral/aortic valve vegetations)

– Secondary infection of traumatic splenic hematoma orinfarct

– Other predisposing risk factors: Recent surgery, otherabdominal infections, intravenous drug abuse,immunodeficiency, malignancy or hematologicdisorders, trauma, diabetes, and pancreatitis

○ Most fungal microabscesses occur in setting ofimmunosuppression, HIV/AIDS, or hematologic disorders

○ Echinococcal infections occur due to infection with

tapeworm (Echinococcus granulosus)

– Most commonly occur in areas with sheep(transmission often via dogs who eat viscera ofslaughtered animals)

– Most common in South America, Middle East, EasternMediterranean, and parts of Africa

○ Unilocular (65%); multilocular or multiple (20%)

○ Gram-negative organisms in 55%: Klebsiella pneumoniae

most common pathogen

• Fungal

○ Typically microabscesses measuring < 1.5 cm (25%)

○ Most often Candida (most common), Aspergillus, and Cryptococcus

○ Tuberculosis (TB) and Mycobacterium avium-intracellulare

(MAI) in AIDS patients

– Lab data: Leukocytosis (66%), positive blood cultures

○ Echinococcal cyst– Many patients are asymptomatic and may remain

– Symptoms depend on site of infection and size of cyst– Lab data: Eosinophilia in only small minority ofpatients (< 15%)

○ Rare: 0.2% of reported autopsies

○ 25% of patients with splenic abscesses areimmunocompromised patients

• Excellent prognosis for pyogenic abscesses inimmunocompetent patient

• Guarded prognosis in immunocompromised patients withfungal microabscesses

• Echinococcal disease can recur many years after treatmentand should be monitored periodically for recurrence

Treatment

• Splenic pyogenic abscess

○ Traditional treatment is splenectomy with spectrum antibiotics

broad-– Still standard treatment in setting of multiplepyogenic abscesses or abscess rupture– Mortality postsplenectomy: 6%

○ Spleen-conserving treatment increasingly being utilized– Antibiotics alone may be curative in 75% of smallpyogenic abscesses (< 4 cm)

– Percutaneous drainage may be utilized for unilocularunruptured abscesses with high reported successrates

• Fungal microabscesses

○ Treatment with antifungal medications

• Echinococcal cyst

○ Treatment options include surgical resection (especially

in setting of ruptured cysts or other complications),percutaneous drainage (± introduction of scolicidalagent), drug therapy (e.g., albendazole), or observationDIAGNOSTIC CHECKLIST

Consider

• Differentiate splenic abscesses from mimics, includinglymphoma, low-density metastases, or splenic infarcts

• Splenic abscesses appear as solitary or multiple attenuation cystic lesions in febrile patient

low-SELECTED REFERENCES

1 Tonolini M et al: Nontraumatic splenic emergencies: cross-sectional imaging findings and triage Emerg Radiol 20(4):323-32, 2013

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557

(Left) Color Doppler image

shows a well-defined solitary splenic abscess with a hypoechoic necrotic center ﬅ and a thick irregular wall ﬆ.

The adjacent splenic parenchyma ﬇ appears normal Note the typical avascular nature of the abscess (Right) Axial T1 C+

MR in a patient with LUQ pain and a fever illustrates the characteristic multiseptate appearance of a splenic abscess ﬅ Blood cultures identified Staphylococcus and the patient recovered with antibiotics.

(Left) Axial CECT in a

29-year-old intravenous drug abuser with a 3-day history of fever and LUQ pain shows a focal hypodense lesion ﬅ in the periphery of the spleen's midportion; findings that are consistent with an abscess.

(Right) Axial CECT in the same

patient reveals lateral perisplenic inflammatory changes ﬅ, suggesting a possible abscess rupture An echocardiogram showed multiple vegetations in both the aortic and mitral valves, suggesting that this abscess is due to underlying

endocarditis.

29-year-old known intravenous drug abuser who presented with multiple skin abscesses as well

as abdominal pain and fever demonstrates a low- attenuation splenic abscess

ﬅ (Right) Axial CECT in the

same patient demonstrates multiple hepatic abscesses ﬅ

as well The patient underwent an echocardiogram, which additionally revealed aortic valve vegetations from endocarditis (not shown).

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Splenomegaly and Hypersplenism

KEY FACTS

TERMINOLOGY

• Splenomegaly: Splenic enlargement caused by a number of

different underlying disorders

IMAGING

• Normal spleen is ≤ 13 cm in length

• Splenic index (product of length, breadth, and width of

○ Hematologic

– Polycythemia vera, myelofibrosis, andhemoglobinopathies

○ Inflammatory/infectious– Mononucleosis and HIV/AIDS most commoninfections to result in splenomegaly– Sarcoid may result in mild splenomegaly with multiplesmall hypodensities in liver and spleen

○ Space-occupying lesions– Space-occupying masses in spleen do not commonlycause splenomegaly and are more likely to replacenormal splenic tissue

○ Storage and infiltrative disorders– Primary or secondary hemochromatosis, amyloidosis,and glycogen storage diseases

CLINICAL ISSUES

• Complications include splenic rupture and hypersplenism

○ Hypersplenism: Hyperfunctioning spleen removesnormal RBC, WBC, and platelets from circulation

(Left) Frontal radiograph

demonstrates "fullness" in the

left upper quadrant The

small, cirrhotic liver with

widened fissures and signs of

portal hypertension, including

splenomegaly and varices ﬆ.

In most patients with

splenomegaly, there are clues

as to the underlying cause on

the imaging study, as in this

case (Right) Coronal CECT in

an asymptomatic patient

demonstrates a mildly

enlarged spleen with multiple

ill-defined hypodense nodules

in a patient with known

sarcoidosis Lymphoma and

metastatic disease could have

a very similar appearance.

Trang 17

• SMG: Splenic enlargement caused by a number of different

underlying congestive, hematologic,

inflammatory/infectious, neoplastic, or infiltrative disorders

• Hypersplenism: Syndrome consisting of splenomegaly and

pancytopenia in which bone marrow is either normal or

hyperreactive

IMAGING

General Features

○ ↑ volume of spleen with convex medial border

• Size

○ No consensus on absolute size thresholds for SMG:

Different sources suggest different measurements

○ Normal spleen is ≤ 13 cm in length

– Width and breadth are usually ≤ 6 and 8 cm,

respectively

○ Splenic index: Normally 120-480 cm³ (product of length,

breadth, and width of spleen)

○ Splenic weight: Splenic index x 0.55

– Normal weight: 100-250 g

○ SMG: Anteroposterior (AP) diameter > 2/3 distance of AP

diameter of abdominal cavity

• Morphology

○ SMG is often associated with abnormal contour of

spleen, including rounding of poles and convexity of

medial border

• Radiography

○ Normal-sized spleen usually not visualized

○ SMG: Splenic tip below 12th rib

○ Marked SMG may displace stomach medially

○ Displacement of splenic flexure of colon (splenic flexure

usually anteromedial to spleen)

CT Findings

• SMG is usually due to 1 of 5 general etiologies

• Congestive

○ Right heart failure: Cardiomegaly with distension of

hepatic veins/IVC and passive hepatic congestion

○ Portal hypertension: Splenomegaly with varices, nodular

shrunken liver, ascites, and other signs of portal

hypertension

○ Splenic or portal vein occlusion or thrombosis (often due

to pancreatitis or pancreatic tumors)

○ Sickle cell disease

– Acute phase: Diffusely decreased splenic density with

○ IV drug abuse: SMG due to chronic low-level sepsis

○ Tuberculosis, histoplasmosis: Multifocal low-densitygranulomas acutely that heal as calcified foci

○ Sarcoidosis: Often associated with innumerable smallhypodense splenic granulomas, ± upper abdominallymphadenopathy, ± hepatomegaly with similarhypodense hepatic granulomas

○ Collagen vascular or autoimmune diseases– Rheumatoid arthritis, scleroderma, etc

– Felty syndrome: Rheumatoid arthritis, splenomegaly,and granulocytopenia

○ Malaria: One of the most common causes of SMGworldwide

• Space-occupying lesions

○ Space-occupying masses do not commonly cause SMGand are more likely to replace normal splenic tissue

○ Cysts: Common, but usually do not cause SMG

○ Lymphoma and metastases: Relatively common cause ofsplenomegaly, especially lymphoma (which may or maynot be associated with discrete hypodense lesions inspleen)

○ Primary splenic tumors: Do not typically cause SMG

• Storage and infiltrative disorders

○ Secondary hemochromatosis– Increased density of liver and spleen on NECT (irondeposition in RES cells)

○ Primary hemochromatosis– Density of spleen is normal (unlike that of liver)

○ Amyloidosis– NECT and CECT: Generalized or focal ↓ density

○ Glycogen storage diseases (e.g., Gaucher disease)

MR Findings

• Portal hypertension

○ Gamna-Gandy bodies or siderotic nodules appear asmultiple tiny (3-8 mm) foci of ↓ T1WI and T2WI signal– Represent hemosiderin deposits related to priormicrohemorrhage

• Hemochromatosis

○ Involved organs (including spleen) are typically markedlylow signal on both T1 and T2WI with signal loss on in-phase gradient echo images

○ Primary: Normal signal and size of spleen, with liver andpancreas most typically involved

○ Secondary: Liver, spleen, bone marrow, and lymph nodesmost often involved

• Sickle cell disease

Trang 18

○ Spleen appears low signal on all pulse sequences due toiron deposition

• Gaucher disease: May present with focal lesions, which

demonstrate either T2WI hypointensity or hyperintensity

• Infarction

○ Peripheral, wedge-shaped areas of abnormal signal thatvary in signal intensity depending on age of infarct andpresence/absence of hemorrhagic transformation– Acute hemorrhagic infarcts may show high T1WIsignal

– Chronic infarcts tend to be low signal on T1WI andhigh signal on T2WI

• Extramedullary hematopoiesis

○ May present with focal T1WI and T2WI hyperintense,homogeneously enhancing nodules within enlargedspleen

○ SMG with normal echogenicity– Infection, congestion (portal hypertension), earlysickle cell disease

– Hereditary spherocytosis, hemolysis, Felty syndrome– Wilson disease, polycythemia, myelofibrosis, leukemia

○ SMG with hyperechoic splenic parenchyma– Leukemia, post chemotherapy and radiation therapy– Malaria, TB, sarcoidosis, polycythemia

– Hereditary spherocytosis, portal vein thrombosis,hematoma, metastases

○ SMG with hypoechoic splenic parenchyma– Lymphoma, multiple myeloma, chronic lymphocyticleukemia

– Congestion from portal hypertension, noncaseatinggranulomatous infection

○ Sickle cell disease: Immediately after sequestration,peripheral hypoechoic areas may be visualized

○ Gaucher disease: Multiple, well-defined, discretehypoechoic lesions representing fibrosis or infarction

○ CECT with multiplanar reformationsDIFFERENTIAL DIAGNOSIS

Other Left Upper Quadrant Masses

• e.g., gastric, renal, adrenal tumors

Splenic Trauma

• Intrasplenic or subcapsular hematoma may enlarge spleen

• Diagnosis usually evident based on imaging and history of

trauma

• Pyogenic (bacterial) abscess

○ Low-density cystic mass with thick, irregular enhancingwall ± internal gas and reactive left pleural effusion

• Fungal (e.g., Candida, Aspergillus, Cryptococcus)

○ Low-density lesions that may be solitary or multiple and

of variable size and may show minimal peripheralenhancement

• AIDS: Pneumocystis, mycobacterial (e.g., Mycobacterium

○ Focal low-attenuation splenic lesions ± calcificationPATHOLOGY

General Features

• Etiology

○ Congestive SMG– CHF, portal hypertension, cirrhosis, cystic fibrosis,splenic vein thrombosis, SC sequestration

○ Neoplasm: Leukemia, lymphoma, metastases, primaryneoplasm, Kaposi sarcoma

○ Storage disease: Gaucher, Niemann-Pick, gargoylism,amyloidosis, hemochromatosis, histiocytosis

○ Infection: Hepatitis, malaria, mononucleosis, TB, typhoid,kala-azar, schistosomiasis, brucellosis

○ Hemolytic anemia: Hemoglobinopathy, hereditaryspherocytosis, primary neutropenia, thrombocytopenicpurpura

○ Extramedullary hematopoiesis: Osteopetrosis,myelofibrosis

○ Collagen disease: SLE, RA, Felty syndrome

○ Most common causes of massive SMG: Lymphoma,chronic myelogenous leukemia, extramedullaryhematopoiesis, myelofibrosis, and Gaucher diseaseCLINICAL ISSUES

Presentation

○ Many patients asymptomatic, but can result inabdominal pain or palpable mass in left upper quadrant

○ Signs and symptoms often related to underlying cause

• Complications

○ Splenic rupture, shock, and death

• Hypersplenism: Usually develops as result of SMG

○ Hyperfunctioning spleen removes normal RBC, WBC,and platelets from circulation

○ Up to 90% of all platelets may be removed fromcirculation by spleen in cases of severe SMG

Treatment

• Treatment varies based on underlying condition

• Splenectomy in symptomatic and complicated casesDIAGNOSTIC CHECKLIST

• Look for imaging findings that may explain a patient'ssplenomegaly, such as the presence of cirrhosis/portalhypertension

SELECTED REFERENCES

1 Manenti A et al: Splenomegaly Secondary to Myeloproliferative Neoplasms and Portal Hypertension Clin Lymphoma Myeloma Leuk ePub, 2014

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561

(Left) Coronal CECT

demonstrates a mildly enlarged spleen with multiple hypodense nodules The patient was later found to have thoracic

lymphadenopathy, and biopsy showed the spleen to be a manifestation of sarcoidosis.

(Right) Axial T2 MR

demonstrates marked low signal in the liver, spleen, and bone marrow in a patient with hemosiderosis due to multiple blood transfusions.

markedly enlarged spleen with multiple subtle low-density foci ﬅ scattered throughout the splenic parenchyma This was found to be lymphoma, and lymphadenopathy was present elsewhere.(Right)

Axial CECT in a patient with non-Hodgkin lymphoma shows splenomegaly and extensive lymphadenopathy ﬈ While splenomegaly and

lymphadenopathy are characteristic findings in patients with NHL, benign processes, such as sarcoidosis and mononucleosis, may result

in similar findings.

(Left) Axial arterial phase

CECT in a patient with cirrhosis & portal hypertension shows a swirled moiré pattern

of splenic enhancement that disappeared on the portal venous phase This normal variant is often more prominent in patients with cirrhosis and portal hypertension (Right) US

shows splenomegaly with multiple hypoechoic foci ﬅ in

a patient with granulomatous MAI infection On US, granulomatous abscesses appear as well-defined, hypoechoic lesions, usually with associated splenomegaly.

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Splenic Infarction

KEY FACTS

TERMINOLOGY

• Global or segmental parenchymal splenic ischemia and

necrosis caused by vascular occlusion

IMAGING

• Acute findings on CECT

○ Diagnosis best made on portal venous phase images due

to heterogeneous arterial phase enhancement

○ Global infarction: Complete nonenhancement of spleen– ± cortical rim sign: Preserved enhancement ofperipheral rim of spleen in massive infarction

○ Segmental infarction: Wedge-shaped or rounded attenuation area usually at periphery of spleen– Can be multiple, especially when caused by emboli

low-• Chronic findings on CECT

○ Most often results in scarring and volume loss

○ Multiple repetitive infarcts in sickle cell disease can lead

to small, calcified spleen (autoinfarcted spleen)

○ Infarct can develop into splenic cyst

• Complications (< 20% of patients)

○ Perisplenic fluid/hematoma suggests splenic rupture

○ Development of rim-enhancing fluid collection: Splenicabscess

• Splenic laceration

• Splenic cyst or abscess

• Heterogeneous arterial phase enhancement of spleen

• Splenic tumors

CLINICAL ISSUES

• Many different causes, but 2 most common are

○ Hematologic disease or hematologic malignancies (sicklecell, myelofibrosis, leukemia, etc.)

○ Embolic conditions (septic emboli, cardiac emboli fromatrial fibrillation, etc.)

• Most cases require no treatment, but rarely surgery orintervention for pain or complications

(Left) Axial CECT in a sickle

cell patient demonstrates an

enlarged spleen with multiple

wedge-shaped acute splenic

infarcts ﬆ While sickle cell

patients can develop a small,

calcified autoinfarcted spleen,

the spleen may be enlarged in

the early stages of the disease.

(Right) Axial CECT

demonstrates a large, global

infarct of the spleen with only

a tiny amount of enhancing

splenic tissue ﬇ Notice the

peripheral enhancement (rim

sign) ﬆ at the margins of the

infarct as a result of preserved

flow through capsular vessels.

67-year-old man with a 10-year history

of atrial fibrillation, now

presenting with acute LUQ

pain, demonstrates a

peripheral, low-attenuation

splenic infarct with straight

margins ﬅ (Right) Axial

CECT in the same patient

identifies a left ventricular

thrombus ﬈ as the source of

the arterial embolus to the

spleen Embolic disease is

likely the most common cause

of splenic infarcts in older

patients.

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• Global or segmental parenchymal splenic ischemia and

necrosis caused by vascular occlusion

IMAGING

General Features

○ Peripheral, wedge-shaped, nonenhancing areas within

splenic parenchyma on CECT in patients with LUQ pain

• Location

○ Entire spleen may be infarcted or more commonly

segmental areas

• Morphology

○ Most commonly wedge-shaped areas of

nonenhancement when infarct is segmental

– Straight margins indicate vascular etiology (rather

than a mass or fluid collection)

– May very rarely be rounded (atypical appearance)

• Radiography

○ May be associated with lower left lobe atelectasis and

pleural effusion on chest x-ray

CT Findings

• NECT

○ Infarcts may be difficult (or impossible) to visualize

without intravenous contrast

○ Areas of hemorrhagic transformation within infarcts

appear hyperdense on NECT

• CECT

○ Acute findings

– Diagnosis best made on portal venous phase images:

Heterogeneous enhancement during arterial phase

(due to differential enhancement of red and white

pulp) makes identification of subtle infarcts difficult

– Global: Complete nonenhancement of spleen

□ ± cortical rim sign: Preserved enhancement of

peripheral rim of spleen in massive infarction due

to preserved flow from capsular vessels

□ Mottled higher density areas within infarcted

spleen may represent either tiny islands of residual

enhancing splenic tissue or hemorrhage

– Segmental: Wedge-shaped or rounded

low-attenuation area usually at periphery of spleen

□ Can be multiple, especially when caused by emboli

□ In some instances, accessory spleens (splenules)

may be infarcted

□ Spleen may or may not be enlarged in acute phase

– Complications (< 20% of patients)

□ Presence of fluid or hematoma surrounding spleen

in setting of infarct suggests splenic rupture (most

often in setting of large or global infarct)

□ Development of discrete rim-enhancing fluid

collection ± internal gas should raise concern for

splenic abscess

○ Chronic findings

– Infarcts should evolve over time, leaving areas of

scarring and volume loss in spleen

□ Sites of old infarcts may show calcification

□ Remaining spleen may undergo compensatoryhypertrophy

– Multiple repetitive infarcts in sickle cell disease canlead to a small, calcified spleen (autoinfarcted spleen)– Infarct can develop into splenic cyst (secondary oracquired cyst)

○ Portal venous phase CECTDIFFERENTIAL DIAGNOSIS

• Unlike infarct, splenic abscess is a discrete, rounded fluidcollection with adjacent fat stranding/inflammation

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Splenic Infarction

○ May develop from evolution of prior infarct

• May appear as multiple small lesions (microabscesses) due

to fungal infections in immunocompromised patients

Normal Heterogeneous Enhancement of Spleen in

Arterial Phase

• Striated appearance of spleen in arterial phase (due to

differential enhancement of red and white pulp) should not

be confused with splenic infarcts

Splenic Tumors

• Primary or secondary neoplasms of spleen (whether benign

or malignant) should appear focal and mass-like, withrounded borders (not wedge-shaped or linear)

• Lymphoma and some metastases (metastatic melanoma or

mucinous neoplasms) may appear low density andhypoenhancing, resembling density of infarctsPATHOLOGY

□ Leukemia and lymphoma

□ Any cause of hypersplenism/splenomegaly(including mononucleosis and infections)– Thromboembolism

□ Pancreatitis or pseudocysts

□ Portal hypertension

□ Any surgical procedure involving upper abdominalorgans (particularly pancreatic tail, stomach, leftadrenal gland)

□ Collagen vascular disease

□ Tumors (gastric, pancreatic, adrenal) involvingsplenic hilum and vessels

CLINICAL ISSUES

Presentation

○ Many patients can be asymptomatic (1/3 of patients)– Most common with small splenic infarcts

○ Most common symptoms: LUQ pain, fever, chills,malaise, nausea, vomiting

○ May be associated with other infarcts (e.g., kidney andbowel) in patients with splenic infarcts due to emboli

• Lab data: Anemia (53%), leukocytosis (41%), elevatedplatelet count (7%)

□ Probably caused by congestion and occlusion ofsplenic vessels by abnormal cells associated withhematologic disorder

□ Most common cause of splenic infarcts overall– Embolic conditions (septic emboli, cardiac embolifrom atrial fibrillation, embolization of ulceratedatherosclerotic plaque); most common cause in olderpatients

• Most cases require no treatment and symptoms ceasenaturally

• Rarely surgery or intervention for pain or complications

○ Complications: Abscess, rupture, subcapsular hematoma,hemorrhage, pseudocyst formation

Treatment

• Asymptomatic: Supportive treatment (pain control withanalgesics)

• Symptomatic: Splenectomy for intolerable/increasing pain

or splenic rupture; image-guided drainage for splenicabscess formation

DIAGNOSTIC CHECKLIST

• Wedge-shaped, peripheral area of nonenhancement onportal venous phase CECT

• Do not confuse normal striated enhancement pattern onarterial phase CECT for splenic infarct

SELECTED REFERENCES

1 Gaetke-Udager K et al: Multimodality imaging of splenic lesions and the role

of non-vascular, image-guided intervention Abdom Imaging 39(3):570-87, 2014

2 Llewellyn ME et al: The sonographic "bright band sign" of splenic infarction J Ultrasound Med 33(6):929-38, 2014

3 Lawrence YR et al: Splenic infarction: an update on William Osler's observations Isr Med Assoc J 12(6):362-5, 2010

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565

Splenic Infarction

(Left) Axial CECT in a young

child with acute abdominal pain demonstrates a large, hypoenhancing mass ﬅ in the pelvis (Right) Coronal CECT in

the same patient again shows the same mass ﬅ in the pelvis with fluid in the adjacent right pelvis ﬆ and no spleen noted

in the abdomen This mass was found at surgery to represent torsion and infarction of a

"wandering" spleen The spleen in such cases is found in ectopic locations due to laxity

or absence of the splenic ligaments.

(Left) A large fluid collection

ﬆ envelops small areas of normal splenic tissue ﬅ This was found at surgery to represent a massively infarcted spleen with contained rupture, resulting in the fluid collection.(Right)

Patient status post embolization for hypersplenism shows severe splenomegaly with no enhancement except for a small portion of the medial spleen ﬆ Massive acute infarction is often not desired

in splenic embolotherapy, as patients can develop infections of infarcted tissue.

(Left) Sagittal ultrasound in a

48-year-old woman with myelodysplastic syndrome and

a 1-week history of LUQ pain shows marked splenomegaly &

a wedge-shaped hypoechoic area ﬅ in the lower pole of the spleen, consistent with infarction The patient was placed on analgesics and recovered uneventfully.

(Right) Axial NECT in a

55-year-old woman presenting with a history of sickle cell anemia demonstrates a spleen that is very small, densely calcified ﬅ, and nonfunctional, sometimes termed "autosplenectomy."

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Splenic TraumaKEY FACTS

• Sentinel clot sign: Highest density blood localizes adjacent

to spleen (or any site of injury)

○ Indicates splenic injury even without demonstrablelaceration

• Parenchymal laceration: Irregular linear, branching, or

stellate area of nonenhancing low attenuation

• Splenic fracture: Deep laceration extending from outercapsule through splenic hilum

• Splenic infarction: Unusual (< 2% of cases) in the setting oftrauma, and can be segmental or complete

• Active arterial extravasation: High-attenuation focusisodense with aorta, surrounded by lower attenuation clot

• Prone to develop delayed hemorrhage, but excellentprognosis with early intervention (surgery/embolization)

• Identification of active arterial extravasation orpseudoaneurysm best predictor of need for surgery andfailure of nonoperative management

(Left) Axial CECT in an

87-year-old woman who fell at a

nursing home demonstrates a

flattening the normal convex

lateral splenic contour,

representing a subcapsular

hematoma ﬊ (Right) Axial

CECT in a 23-year-old man

injured in a motor vehicle

accident shows a shattered

spleen with a sentinel clot ﬅ

in the perisplenic region and

large hemoperitoneum ﬉.

19-year-old man who was an

unrestrained passenger in a

motor vehicle accident shows

marked upper abdominal

hemoperitoneum ﬅ, a

shattered spleen with

intrasplenic high-attenuation

pseudoaneurysms ﬆ, and a

focus of active arterial

extravasation lateral to the

spleen within the peritoneal

cavity ﬇ (Right) Axial CECT

in the same patient shows the

active arterial extravasation

ﬅ extending into the left

paracolic gutter with

surrounding hemoperitoneum

ﬆ.

Trang 25

○ Low-attenuation splenic laceration with high-density

active bleeding

• Radiography

○ Abdominal radiography

– Left upper quadrant soft tissue mass

– Signs of intraperitoneal fluid with widening of

distance between flank strip and descending colon

– Fluid in pelvis with prominent pelvic "dog ears"

○ Chest radiography demonstrates associated injuries

– Lower left lobe atelectasis &/or consolidation

– Left rib fractures, pneumothorax, pleural effusion

□ Perisplenic hematoma: Located adjacent to spleen

and implies disruption or rupture of splenic capsule

□ Intraparenchymal hematoma: Typically round,

ovoid, or irregular in shape

□ Subcapsular hematoma: Constrained by splenic

capsule; crescentic in shape and compresses lateral

margin of parenchyma

○ Sentinel clot sign: Highest density blood localizes

adjacent to spleen (or any site of injury)

– Indicates splenic injury even in absence of

demonstrable laceration

○ Layered or lamellated clot if bleeding is intermittent

• CECT

○ Parenchymal laceration: Irregular linear, branching, or

stellate area of nonenhancing low attenuation within

○ Splenic fracture: Deep laceration extending from outer

capsule through splenic hilum

○ Splenic infarction: Unusual (< 2% of cases) in setting of

trauma

– Can be segmental or complete

– Wedge-shaped area of hypoattenuation

– Due to arterial thrombosis after intimal injury

– Risk of delayed rupture or abscess formation

○ Active arterial extravasation: High-attenuation focusisodense with aorta, surrounded by lower attenuationclot or hematoma

– May be linear (spurting vessel) or rounded(pseudoaneurysm): Distinction is made using delayedphase images

□ Active extravasation (unlike pseudoaneurysm)changes in size and morphology between initial anddelayed phases

□ Although delayed images are not routinely included

in most trauma protocols, addition of delayedimages can be helpful if there is site of suspicionnoted on initially acquired portal venous phaseimages

Splenic Cleft

• Normal anatomic variant that appears as a thin, fissure-likeband of low attenuation

• Most often occurs at upper or lower pole of spleen

• No evidence of adjacent hematoma, free fluid, or stranding

Trang 26

• Rounded, nonenhancing cystic lesion with definable cyst

wall ± peripheral calcificationPATHOLOGY

General Features

• Etiology

○ Most commonly due to blunt trauma with blow to leftupper quadrant (LUQ)

– Motor vehicle collisions most common cause

○ Penetrating trauma to spleen less common

○ Rarely iatrogenic trauma to spleen during surgery(particularly colon surgery)

○ Increased risk of splenic injury in patients withsplenomegaly (from any cause)

• Associated abnormalities

○ Injuries to left thorax, tail of pancreas, left liver lobe, &/ormesentery

Staging, Grading, & Classification

• Grading may be misleading: "Minor" injuries may go on to

devastating delayed bleed or delayed rupture

• AAST (American Association for Surgery of Trauma) grading

system is based on extent of injury at laparotomy andapplied to CT findings

○ Does not take into account active extravasation andpseudoaneurysm formation

○ I: Subcapsular hematoma (< 10% of surface area ofspleen) or laceration < 1 cm

○ II: Subcapsular hematoma (10-50% of surface area ofspleen) or laceration 1-3 cm

○ III: Subcapsular hematoma (> 50% of surface area ofspleen), parenchymal hematoma > 5 cm or expandinglaceration > 3 cm or involving trabecular vessels,ruptured subcapsular or parenchymal hematoma

○ IV: Laceration involving segmental or hilar vessels withdevascularization/infarct of at least 25% of spleen

○ V: Shattered spleen; hilar vascular injury with completedevascularization/infarct of spleen

• Marmery MDCT-based grading system

○ I: Subcapsular hematoma (< 1 cm thick), laceration (< 1

cm in depth), or parenchymal hematoma (< 1 cm indiameter)

○ II: Subcapsular hematoma (1-3 cm thick), laceration (1-3

cm in depth), or parenchymal hematoma (1-3 cm indiameter)

○ III: Subcapsular hematoma (> 3 cm thick), laceration (> 3

cm in depth), or parenchymal hematoma (> 3 cm indiameter); splenic capsular rupture

○ IVA: Active extravasation in intraparenchymal orsubcapsular hematoma; pseudoaneurysm orarteriovenous fistula; shattered spleen

○ IVB: Active intraperitoneal bleedingCLINICAL ISSUES

Presentation

○ Blunt abdominal trauma, LUQ pain, hypotension– Often associated with left chest pain due to ribfractures, left lower lobe lung consolidation, or lefthemothorax

– Injury to other abdominal organs in 36.5%

– 80% with splenic injury have extra-abdominal injuries

Demographics

• Epidemiology

○ Most commonly injured solid abdominal organ in blunttrauma

○ Most common abdominal organ injury requiring surgery

• Prone to develop delayed hemorrhage, but excellentprognosis with early intervention (surgery/embolization)

• Identification of active arterial extravasation orpseudoaneurysm best predictor of need for surgery andfailure of nonoperative management

Treatment

• Hemodynamically unstable patients with splenic injuryundergo surgery if focused assessment with sonographyfor trauma (FAST) scan or diagnostic peritoneal lavage(DPL) are positive

○ 29% of all patients and 40% of children may not havehemoperitoneum and DPL/FAST may be falsely negative

• Hemodynamically stable patients with AAST grade I-IIIsplenic injury and without other injuries oftenconservatively (observation or embolization) managed

○ Conservative management in up to 70% of cases

○ Avoids risks of surgery and post-splenectomy sepsis

○ Active extravasation, pseudoaneurysm, orhemoperitoneum in hemodynamically stable patientsmanaged with embolization

○ Embolization generally not utilized for higher grade (> III)injuries and older patients → splenectomy

○ Splenectomy in higher grade injuries, hemodynamicinstability, or failed conservative management (delayedsplenic rupture)

• Nonoperative management generally preferred in pediatricpatients

1 Uyeda JW et al: Active hemorrhage and vascular injuries in splenic trauma: utility of the arterial phase in multidetector CT Radiology 270(1):99-106, 2014

2 Boscak AR et al: Optimizing trauma multidetector CT protocol for blunt splenic injury: need for arterial and portal venous phase scans Radiology 268(1):79-88, 2013

3 Post R et al: Computed tomography blush and splenic injury: does it always require angioembolization? Am Surg 79(10):1089-92, 2013

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569

Splenic Trauma

39-year-old woman who sustained multiple injuries in a motor vehicle accident shows the irregular and linear areas of decreased enhancement ﬈ within the spleen.(Right)

Axial CECT in the same patient again illustrates the areas of decreased enhancement within the spleen ﬈, as well

as a small perisplenic hematoma ﬇ in this typical case of splenic laceration.

splenic fracture with active extravasation Note the fracture of the lower pole ﬅ featuring a site of high- attenuation arterial extravasation ﬇.(Right)

Axial CECT in the same patient demonstrates a large perisplenic hematoma ﬆ and extensive arterial

extravasation ﬇.

(Left) Axial CECT in a young

man injured in a motor vehicle accident shows a splenic parenchymal laceration ﬅ with a high density clot ﬆ adjacent to the spleen.(Right)

Axial CECT in the same patient again illustrates the clot adjacent to the spleen ﬆ, as well as lower density and more homogeneous blood elsewhere within the peritoneal cavity ﬇ This is characteristic of the sentinel clot sign The injury healed without surgical intervention.

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SplenosisKEY FACTS

TERMINOLOGY

• Dissemination of splenic tissue into ectopic locations

following splenic rupture (either traumatic or iatrogenic)

IMAGING

• Can occur in virtually every compartment of body

○ Most common in abdomen/pelvis (65% of cases)

○ Usually located within peritoneal cavity (greateromentum, bowel serosa, parietal peritoneum,undersurface of diaphragm)

○ Less common locations include thorax (usually afterdiaphragmatic rupture) and subcutaneous soft tissues

• MDCT: Multiple nodules or masses scattered throughout

abdomen or pelvis (usually peritoneal cavity)

○ Should follow appearance of spleen on all phases ofenhancement

○ Slightly hypoattenuating (5-10 HU less) compared to liver

on NECT, striated enhancement on arterial phase, andhomogeneous enhancement on venous/delayed phases

• MR: Follows appearance and enhancement of normalspleen on all sequences

• Tc-99m heat-denatured RBC scan: ↑ sensitivity/specificity

○ ↑ uptake within nodules

• No other clinical significance in most cases

• Most patients are asymptomatic, but rarely, symptoms aredue to hemorrhage, rupture, torsion, infarction, or bowelobstruction

(Left) Axial CECT

demonstrates absence of the

spleen (patient had a history

of prior splenectomy for

trauma) with small enhancing

nodules ﬅ in the left upper

quadrant Splenosis is not

infrequently seen in close

proximity to the splenectomy

bed (Right) Axial CECT in the

same patient shows additional

splenic implants ﬅ along the

serosal surface of the left

colon and along the posterior

margin of the right liver lobe.

Splenosis is most commonly

seen within the peritoneal

cavity, with extraperitoneal

splenosis more rare.

with remote history of

abdominal trauma shows

multiple soft tissue nodules ﬅ

along the peritoneal surfaces,

which might be mistaken for

carcinomatosis, but represent

splenosis (Right) Axial CECT

shows an enhancing soft

tissue nodule ﬅ in the left

cardiophrenic angle The

patient had a distant history

of traumatic splenic injury

with diaphragmatic rupture,

the most common reason for

thoracic splenosis Thoracic

splenosis is quite rare

compared to abdominal/pelvic

splenosis.

Trang 29

• Dissemination of splenic tissue into ectopic locations

following splenic rupture (either traumatic or iatrogenic)

IMAGING

General Features

• Location

○ Most common in abdomen/pelvis (65% of cases)

– Usually located within peritoneal cavity (greater

omentum, bowel serosa, parietal peritoneum,

undersurface of diaphragm)

– Involvement of extraperitoneal spaces uncommon

○ Can occur in virtually every compartment of body

– Less common locations include thorax (usually after

diaphragmatic rupture), subcutaneous soft tissues,

and even intracranial cavity

CT Findings

• Multiple nodules scattered throughout abdomen or pelvis

• Nodules follow appearance of spleen on all phases

○ Slightly hypoattenuating (5-10 HU less) compared to liver

on NECT, striated enhancement on arterial phase, and

homogeneous enhancement on venous/delayed phases

MR Findings

• Follows signal/enhancement of spleen on all sequences

• T1WI: Hypointense to liver; slightly hyperintense to muscle

• T2WI: Hyperintense to liver

• Nonspecific round/oval, homogeneous mass(es)

• PET

○ Splenosis nodules can be FDG avid and mimic neoplasm

• Tc-99m sulfur colloid

○ ↑ uptake within splenic nodules (similar to native spleen)

• Tc-99m labeled heat-denatured RBC scintigraphy

○ ↑ sensitivity/specificity with ↑ uptake within nodules

○ Tc-99m labeled heat-denatured RBC scan

Peritoneal Carcinomatosis

• Usually associated with ascites, omental/peritoneal

stranding and nodularity, and known history of underlying

malignancy

Accessory Spleen

• Congenital ectopic splenic tissue due to failure in fusion of

splenic foci during development

• Most cases are small, solitary, and adjacent to splenic hilum

• May hypertrophy after splenectomy and mimic splenosis

Polysplenia

• Multiple small spleens associated with abdominal situs

inversus and cardiovascular anomalies

Visceral Mass or Malignancy

• Splenosis can mimic pancreatic, adrenal, renal, and gastricmasses (and vice versa)

○ Splenosis abutting pancreatic tail can mimicneuroendocrine tumor

• CT/MR enhancement characteristics and nuclearscintigraphy helpful in differentiation

Peritoneal Endometriosis

• Soft tissue nodules with variable enhancement usuallylocated in pelvis (uterine ligaments, cul-de-sac, fallopiantubes, etc.)

– Hematogenous spread may also play a role

○ Does not occur after elective splenectomy (no rupture ofcapsule)

Gross Pathologic & Surgical Features

• Reddish-blue color; no capsule

• Supplied by small perforating vessels from local tissues

○ Not supplied by splenic artery branches, unlike splenule

Microscopic Features

• May completely resemble normal splenic tissue

○ Cannot differentiate from splenule based on histologyCLINICAL ISSUES

Presentation

• Most are asymptomatic

• Rarely symptomatic due to hemorrhage, rupture, torsion,infarction, or bowel obstruction

Demographics

• Epidemiology

○ Most cases reported in adults; M > F (↑ trauma in men)

○ ~ 70% of patients with splenectomy following trauma

○ Usually detected years after trauma

• No clinical significance in most cases

• Recurrent disease after splenectomy with hematologicdisorders (idiopathic thrombocytic purpura, lymphoma,etc.)

• No Howell-Jolly bodies, Heinz bodies, or abnormal RBCs onperipheral blood smear despite splenectomy

○ Indicates patient has functioning spleen

Treatment

• In most cases, no treatment is necessary

• Surgical resection only if complications or symptoms arepresent

SELECTED REFERENCES

1 Diop AD et al: CT imaging of peritoneal carcinomatosis and its mimics Diagn Interv Imaging ePub, 2014

Trang 30

Splenic CystKEY FACTS

○ Some cysts can have septations, trabeculations, thickwall, internal necrotic debris, or calcification

– May have attenuation greater than simple fluid (due

to hemorrhage or protein)– Thin eggshell calcification or thick, irregular peripheralcalcification

○ Congenital and acquired cysts may be indistinguishable– Congenital cysts more likely simple in appearance– Acquired cysts often complex with calcification

• Splenic infection and abscess

• Splenic metastases and lymphoma

• Benign primary splenic tumors

• Intrasplenic pseudocyst

PATHOLOGY

• Congenital epidermoid ("true" cyst)

○ May be due to intrasplenic sequestration of peritonealmesothelial cells during embryologic development

• Acquired cysts (secondary/"false" cysts or pseudocysts)

○ Due to prior trauma, hematoma, infarction, or infection

○ Arise due to liquefactive necrosis and cystic change

CLINICAL ISSUES

• Most cysts discovered incidentally on imaging

• Small and asymptomatic: No treatment

• Symptomatic cysts usually treated, with options includingpercutaneous aspiration/drainage, cyst decapsulation orunroofing, and partial/complete splenectomy

○ Splenectomy for symptomatic large cysts (> 5 cm)

water density mass with a

calcified wall ﬈ within the

spleen Note the absence of

any enhancing or soft tissue

components within this splenic

cyst (Right) Postsplenectomy

specimen in the same patient

shows the calcified, fibrous

wall of the cyst This was an

acquired cyst, probably as a

result of prior trauma or

infarction.

(Left) Coronal CECT in a young

woman demonstrates a large,

simple-appearing splenic cyst

ﬆ The patient was

symptomatic with pain and

early satiety and consequently

underwent surgical cyst

deroofing (Right) Axial CECT

demonstrates a large,

nonenhancing, multiseptated

splenic cyst ﬆ replacing most

of the spleen Only a posterior

sliver of normal spleen

remains ﬅ.

Trang 31

○ Sharply defined, spherical cystic lesion of water density

• Key concepts

○ Classification

– Congenital epidermoid cysts (primary or "true" cyst)

□ Demonstrate inner cellular endothelial lining

□ Account for 10-25% of all splenic cysts

– Acquired cysts (secondary or "false" cysts)

□ No inner cellular lining, but have fibrous wall

□ Account for 80% of splenic cysts

□ Due to prior trauma, hematoma, or infarction

• Curvilinear wall calcification in left upper quadrant

CT Findings

• Spectrum of appearances

○ Solitary, well-defined, water density unilocular cyst

– Thin wall with sharp interface to normal splenic tissue

– No peripheral or intracystic enhancement; no solid,

nodular soft tissue component

– Always intraparenchymal (no exophytic component)

○ Some cysts can have septations, trabeculations, thick

wall, and internal necrotic debris

– May have attenuation greater than simple fluid (due

to hemorrhage or protein)

○ Cysts may have thin eggshell calcification or thick,

irregular peripheral calcification

• Congenital and acquired cysts may be indistinguishable

○ Congenital cysts more likely to be simple in appearance

○ Acquired cysts more likely complex with calcification

MR Findings

• Most cysts are T2 hyperintense and T1 hypointense

• May have ↑ signal intensity on T1WI due to blood products

or protein within cyst (especially if ↑ attenuation on CT)

• Anechoic with smooth margins and thin walls

• May have internal echoes, septations, and debris

• Peripheral echogenic calcifications ± acoustic shadowing

• Pyogenic abscess

○ Solitary or multiple, with well-defined irregular borders,

peripheral enhancement, and central fluid density

○ ± internal gas due to gas-forming organism

○ Usually clinical history of fever, ↑ WBC, and pain

• Fungal abscess

○ Usually microabscesses with tiny, hypodense nodules

throughout spleen

• Parasitic echinococcal or hydatid cyst

○ Complex cyst with internal low-density "daughter" cysts

and thick wall composed of fibrous tissue

○ Often serpiginous, linear densities within cyst due to

collapsed parasitic membranes

○ Chronic cysts often demonstrate peripheral orserpiginous, wavy internal calcification

○ May be associated with similar cystic lesions in liver andperitoneal cavity

Splenic Metastases and Lymphoma

○ Discrete masses are hypodense and homogeneous

Benign Primary Splenic Tumors

• Most commonly hemangioma and lymphangioma

• May appear solid or cystic, and can appear completelysimple and indistinguishable from splenic cyst

• Hemangiomas may be hypervascular on arterial phase CECT

• Lymphangiomas may be multiloculated with septations

○ Acquired cysts (secondary/"false" cysts or pseudocysts)– Most often due to prior trauma, hematoma,infarction, or infection (including mononucleosis)– Due to liquefactive necrosis and cystic changeCLINICAL ISSUES

Presentation

○ Most cysts discovered incidentally on imaging performedfor other reasons

○ Rarely present with pain or palpable mass

• Complications are rare and include intracystic hemorrhage,rupture, or superinfection

Treatment

• Small and asymptomatic → no treatment

• Symptomatic cysts usually treated, with options includingpercutaneous aspiration/drainage, cyst decapsulation orunroofing, and partial/complete splenectomy

○ Splenectomy for symptomatic large cysts (> 5 cm)SELECTED REFERENCES

1 Rana AP et al: Splenic epidermoid cyst - a rare entity J Clin Diagn Res.

8(2):175-6, 2014

Trang 32

– May be multiple as part of generalized angiomatosis(Klippel-Trenaunay-Weber syndrome)

○ Lymphangioma: Thin-walled, low-density or cystic lesion(can be solitary or multiple) with sharply defined margins

○ Hamartoma: Rare benign tumor of spleen withnonspecific imaging appearance

– Heterogeneous early enhancement which may persistand become more homogeneous on delayed images

• Malignant tumors

○ Primary lymphoma: Most often non-Hodgkin lymphoma(B-cell origin), but much less common than secondarylymphomatous involvement of spleen

– Imaging patterns including enlarged spleen withoutdiscrete mass, solitary dominant hypodense mass, ormultifocal hypodense lesions

○ Angiosarcoma: Rare, highly aggressive malignant tumor

of spleen, with propensity for early, widespreadmetastases (patients usually die within 1 year)– Often multiple lesions with variable enhancementthat may superficially resemble hemangiomas

(Left) Axial CECT in the

arterial phase demonstrates

an incidentally noted splenic

mass ﬆ with a hypervascular

rim of peripheral

enhancement (Right) Axial

CECT in the same patient in

the venous phase

demonstrates that the mass

ﬆ now shows homogenous

enhancement with central

fill-in While the typical nodular,

centripetal enhancement seen

with hepatic hemangiomas is

less common in the spleen,

splenic hemangiomas often

lesions in the spleen,

compatible with multiple

hemangiomas, a classic finding

in this disorder.(Right)

Ultrasound demonstrates an

incidentally identified

echogenic mass ﬅ arising

from the spleen, classic for a

splenic hemangioma Note the

central hypoechoic scar, a

common feature of larger

hemangiomas.

Trang 33

– Most common primary benign neoplasm of spleen,

with autopsy incidence: 0.03-14%

– Primarily affects adults with peak age 35-55 years

– Large hemangiomas may cause splenomegaly and

spontaneous rupture has been reported (very rare)

– May be multiple as part of generalized angiomatosis

(Klippel-Trenaunay-Weber syndrome)

○ Lymphangioma

– Rare, slow-growing benign splenic neoplasm

□ Most lymphangiomas occur in childhood

– Can be either solitary or multiple, but often are

subcapsular in location

– Lymphangiomatosis: Diffuse lymphangiomas (usually

in children)

○ Hamartoma

– Rare benign tumor of spleen with autopsy incidence

of 0.13% and female predominance

□ Mass comprises disorganized vascular channels

mixed with either splenic red pulp or white pulp

– More common in tuberous sclerosis and

Wiskott-Aldrich syndrome

○ Sclerosing angiomatoid nodular transformation

(SANT)

– Rare benign splenic lesion representing abnormal

stromal response to splenic insult with nodular

transformation of splenic vascular bed

– Most common in middle-aged female patients

– Almost always incidental finding, but can result in

splenomegaly and abdominal pain when large

○ Littoral cell angioma

– Rare benign vascular neoplasm arising from littoral

cells lining splenic sinuses of red pulp

– No clear gender or age predilection reported

○ Angiomyolipoma (AML)

– Extremely rare lesion usually in patients with tuberous

sclerosis or multiple renal angiomyolipomas

○ Primary lymphoma (limited to spleen)

– Most common malignant tumor of spleen, but much

less common than secondary involvement of spleen

by widespread lymphoma

– Most often non-Hodgkin lymphoma (B-cell origin)

– Can occur sporadically or in association with AIDS

– More often affects younger population than

secondary (widespread, nodal) lymphoma

○ Angiosarcoma

– Very rare malignant tumor of spleen, but most

common primary nonlymphoid vascular malignant

tumor of spleen

□ Seen sporadically and in patients with previous

exposure to Thorotrast or other toxins

□ Usually affects older individuals (mean age: 50-59and M = F)

– Extremely poor prognosis with early, widespreadmetastases (patients usually die within 1 year)– Metastases most commonly affect liver (70%), lung,pleura, nodes, bone, and brain (30%)

CT Findings

• Benign tumors

○ Hemangioma– Homogeneous solid or cystic mass which may besolitary or multiple

□ Early peripheral and late central enhancement(classic peripheral nodular enhancement seen inhepatic hemangiomas often not present)

□ Some lesions may demonstrate homogeneoushyperenhancement on arterial phase withpersistent enhancement on delayed imaging

□ May rarely be heterogeneous with cysticcomponents, and large lesions may have centralscar/necrosis (as with large hepatic hemangiomas)– Central punctate or peripheral curvilinear Ca++ may

be present

○ Lymphangioma– Thin-walled, low-density or cystic lesions with sharplydefined margins

– Walls of lesions may show faint enhancement, buttypically no wall thickening or nodularity

– May demonstrate curvilinear peripheral calcification

○ Hamartoma– Small lesions appear as isodense or hypodense solidmass (which may have some internal cystic

components)– Large lesions may demonstrate areas of ↓ density(scar or necrosis) or calcification and may distortsplenic contour

– Enhancement: Variable, but lesions appear moreuniform on delayed scans

– May rarely demonstrate calcification

○ Sclerosing angiomatoid nodular transformation(SANT)

– Well-circumscribed, hypodense, solid mass which ishypodense on noncontrast and early phase imagingand gradually becomes isodense on delayed imaging

○ Littoral cell angioma– Multiple hypodense masses of varying size (few mm

to several cm)– May demonstrate delayed enhancement

○ Angiomyolipoma– Fat density mass similar to appearance in kidney withvariable internal enhancement depending on internalmixture of fat, smooth muscle, and vasculature

○ Lymphoma– Several imaging patterns including enlarged spleenwithout discrete mass, solitary dominant hypodensemass, or multifocal hypodense lesions

□ Discrete masses or areas of infiltration usuallyhypoenhancing relative to normal spleen– Focal lesions ↑ common in AIDS-related lymphoma

Trang 34

Primary Splenic Tumors

– Lesions are classically homogeneously hypodense, butmay rarely appear necrotic or cystic

○ Angiosarcoma– Splenomegaly with either solitary dominant mass ormultiple lesions with irregular margins

– Heterogeneous and variable enhancement: Individuallesions may superficially resemble hemangiomas– Spleen may appear heterogeneous due tohemorrhage and calcification

– Propensity to bleed, with intrasplenic, subcapsular, orperisplenic hematoma possible

– Frequent extensive liver or distant metastases

MR Findings

• Benign tumors

○ Hemangioma– Hypointense on T1WI and brightly hyperintense onT2WI (similar to hepatic hemangiomas)

– May show delayed enhancement, but classicperipheral nodular enhancement seen in hepatichemangiomas often not present

○ Lymphangioma– Follow fluid signal: T2 hyperintense and T1hypointense

○ Hamartoma– Isointense on T1WI and heterogeneouslyhyperintense on T2WI (but less T2 hyperintensecompared to hemangiomas)

– Heterogeneous early enhancement which may persistand become more homogeneous on delayed images

○ Sclerosing angiomatoid nodular transformation– Tend to be T2 hypointense with central scar

○ Littoral cell angioma– Multiple T1 hypointense and T2 hyperintense lesions– Lesions may demonstrate internal hemosiderin withhypointensity on T1WI and T2WI

○ Lymphoma– Typically low to intermediate signal on T1WI and mild

to moderate high signal on T2WI– Lesions are hypoenhancing on all phases of imaging

○ Angiosarcoma– T1WI and T2WI: Variable signal due to hemorrhage,necrosis, and calcification (usually hypointense onT1WI and heterogeneously hyperintense on T2WI)– T1 C+: Variable or ring-like enhancement, but mayshow enhancement pattern similar to hemangiomas

○ Hemangioma– Typically homogeneously hyperechoic (as in liver), butcan appear complex with solid and cystic areas

○ Lymphangiomas– Multiloculated cystic appearance ± internal echoes

○ Hamartoma– Well-defined, homogeneous, and echogenic mass

○ Littoral cell angioma– Well-defined hypoechoic or isoechoic mass withmultiple lesions frequent

○ Lymphoma

– Involved portions of spleen appear hypoechoic

○ Angiosarcoma– Solid mass with mixed echogenicity

• CECT or MRDIFFERENTIAL DIAGNOSIS

• Spleen often involved secondarily in lymphoma Hodgkin > Hodgkin disease)

(non-• Spleen is uncommon, but not rare site of metastasis

○ Isolated metastasis to spleen (in absence of metastaticdisease elsewhere) is extremely rare

• May be pyogenic, parasitic, fungal (microabscesses), or due

○ Most benign splenic tumors are incidental findings onimaging studies performed for other reasons– May be rarely symptomatic due to size/mass effect

○ Splenic malignancies may present with LUQ pain,palpable mass, splenomegaly, fever, weight loss

Treatment

• Suspicious tumors (based on either imaging or clinicalhistory) should undergo biopsy ± splenectomyDIAGNOSTIC CHECKLIST

Consider

• Appearance of most splenic tumors is nonspecific, andbiopsy or splenectomy must be considered based on clinicalhistory and degree of suspicion on imaging

SELECTED REFERENCES

1 Thipphavong S et al: Nonneoplastic, benign, and malignant splenic diseases: cross-sectional imaging findings and rare disease entities AJR Am J Roentgenol 203(2):315-22, 2014

Trang 35

577

multiloculated cystic mass ﬅ with thin walls and near- water-density contents, a typical appearance for a splenic lymphangioma.(Right)

Axial CECT in an 18-year-old girl with splenomegaly shows innumerable near-water- density masses within the spleen, which is markedly enlarged as a result The lesions have septations and subtle mural nodularity.

Resection of the spleen revealed dozens of lymphangiomas.

partially calcified splenic mass

ﬅ in a patient with left upper quadrant pain No

lymphadenopathy or other extrasplenic pathology was evident This proved to be primary non-Hodgkin lymphoma (Right) Axial T1 C+

FS MR demonstrates a large, centrally necrotic,

hypervascular mass ﬅ in the spleen, ultimately found to be

a large splenic angiosarcoma.

While the mass ﬆ in the liver superficially resembles a hemangioma, the liver lesion was one of multiple metastases in this patient.

(Left) Axial CECT shows

multiple hypodense lesions ﬅ

in the liver and spleen.

Although they resemble hemangiomas with nodular enhancement, these were found to represent metastatic angiosarcoma Note the additional metastases in the retroperitoneum ﬆ and right lung base ﬇ (Right) Axial

CECT shows a large, hypodense splenic mass ﬅ.

The size of the mass raised concern for malignancy and precipitated splenectomy, where the lesion was found to

be sclerosing angiomatoid nodular transformation.

Trang 36

○ Relatively uncommon with autopsy incidence of 7%

○ Most common pathway of spread is hematogenous viasplenic artery, but can less commonly spread retrogradevia splenic vein or direct splenic invasion

○ Most common primary sites of malignancy: Breast (21%),lung (18%), ovary (8%), stomach (7%), melanoma (6%)

○ Most common multiple lesions (~ 60% of cases)

○ Appearance varies depending on primary malignancy,but most commonly hypoattenuating and solid– Some metastases can appear "cystic" and be mistakenfor cyst or abscess: Melanoma, breast, ovary, andendometrium

○ Almost always evidence of metastatic disease elsewhere:

Isolated metastasis to spleen is extremely rare

– Involved regions of spleen typically appearhypodense, homogeneous, and poorly enhancing– Lesions can uncommonly demonstrate necrosis orcystic degeneration (usually after treatment)– Splenomegaly alone cannot be used to diagnosesplenic involvement

□ 30% of normal-sized spleens harbor tumor inlymphoma patients, and splenomegaly can bepresent without tumor

• Primary splenic tumors

• Splenic infarction or infection/abscess

• Sarcoidosis

• Artifact

(Left) Axial CECT

demonstrates a solid,

hypodense mass ﬆ in the

spleen The lesion was

discovered to be lymphoma at

biopsy No other disease was

present elsewhere This was a

rare instance of primary

splenic lymphoma.(Right)

Axial CECT demonstrates a

mixed cystic and solid mass ﬅ

centered in the spleen that

was found to represent

lymphoma The cystic

components within the mass

are unusual prior to

treatment, as lymphoma

usually appears as a solid

hypodense mass.

(Left) Coronal CECT in a

patient with known lymphoma

demonstrates a markedly

enlarged spleen with

innumerable tiny hypodense

nodules throughout This

"miliary" pattern of disease is

a common manifestation of

splenic lymphoma.(Right)

Axial CECT shows innumerable

focal lesions in the liver and

spleen Liver biopsy confirmed

non-Hodgkin lymphoma.

Diffuse involvement of spleen

(or liver) may be difficult to

recognize on imaging, often

appearing as nonspecific

organomegaly.

Trang 37

– Relatively uncommon with autopsy incidence of 7%

– Most common pathway of spread is hematogenous

(via splenic artery), but can less commonly spread

retrograde via splenic vein (portal HTN) and

lymphatics

– Most common primary sites of malignancy: Breast

(21%), lung (18%), ovary (8%), stomach (7%),

melanoma (6%), prostate (6%)

□ Frequency of splenic metastases by primary tumor:

Melanoma (34%), breast (12%), lung (9%)

– Direct invasion of spleen may occur in gastric cancer,

colon cancer, pancreatic tail cancer, left renal cell

carcinoma, neuroblastoma, or retroperitoneal

sarcoma

– Serosal implants on surface of spleen: Ovarian, GI

tract, pancreatic cancers

○ Splenic lymphoma

– Most common malignant tumor of spleen

□ Spleen can be involved by both Hodgkin disease

(HD) and non-Hodgkin lymphoma (NHL)

– Primary lymphoma far more rare than secondary

lymphoma

□ Accounts for only 1-2% of all cases of lymphoma

□ Primary splenic lymphoma most often NHL (B-cell

origin/diffuse large B cell)

□ More commonly seen in younger patients

compared to secondary lymphoma

– Spleen commonly secondarily involved by lymphoma

(i.e., lymphadenopathy or extranodal disease

elsewhere)

□ Spleen initially involved in 1/3 of HD and 30-40% of

patients with NHL

□ Spleen is considered "nodal" organ in HD and

"extranodal" organ in non-Hodgkin lymphoma

□ Splenic involvement can upstage disease in HD

because it is considered a "nodal organ," while it is

less likely to do so in NHL since spleen is usually

involved in patients with widespread disease

○ Attenuation varies depending on primary malignancy

type, but most commonly hypoattenuating and solid

– Some can appear cystic (homogenously low density)

and be mistaken for cyst or abscess: Melanoma, breast

adenocarcinoma, ovary, and endometrium

– May be multiple (~ 60%) or single (~ 30%)

– Most metastases to spleen do not calcify except

mucinous colon cancer

○ Almost always evidence of metastatic disease elsewhere:

Isolated metastasis to spleen is extremely rare

• Splenic lymphoma

○ Several possible imaging patterns– Homogeneously enlarged spleen without discretemass

□ Spleen may appear totally normal or appeardiffusely hypodense and poorly enhancing (withloss of moire pattern on arterial phase imaging)

□ Diffuse infiltration most common with HD– Solitary dominant mass

– Multifocal involvement with several discrete lesionsmeasuring 1-10 cm in size

□ Focal lesions more likely in AIDS-related lymphoma– Miliary disease with innumerable tiny splenic nodulesmeasuring < 5 mm

○ Involved regions of spleen typically appear hypodense,poorly enhancing on CECT, and relatively homogeneous– Although uncommon, lesions can rarely demonstratenecrosis or cystic degeneration (usually aftertreatment)

– Calcifications are almost never present prior totreatment

– Splenomegaly alone cannot be used to diagnosesplenic involvement

□ 30% of normal-sized spleens can harbor tumor inpatients with lymphoma, and splenomegaly can bepresent without tumor infiltration

□ Greatest degree of splenomegaly often seen withmarginal zone lymphomas

○ Lymphadenopathy (abdominal or retroperitoneal)usually present

– Splenic hilum lymphadenopathy is very common inNHL (59%), but uncommon in HD

MR Findings

• Splenic metastases

○ T1WI: Usually isointense to hypointense, althoughmelanoma metastases may be hyperintense on T1WIdue to melanin content

○ T2WI: Usually hyperintense

○ T1 C+: Enhancement depends on type of primary tumor,but most commonly hypoenhancing

○ Lesions are hypoenhancing to normal splenicparenchyma on T1WI C+ images (usually best visualized

on venous or delayed phases)

○ Splenic metastases– Lesions can vary in echogenicity (usually hypoechoic)

□ "Target" or "halo" morphology should raise concernfor metastasis

– Echogenic lesions (rare): e.g., plasmacytoma,hepatoma, melanoma, prostate, and ovarian cancer

○ Splenic lymphoma– Typically diffuse or focal hypoechoic lesions whichmay have "target" morphology

Trang 38

– Discrete lesions may not be visible, and spleen mayappear heterogeneous or diffusely hypoechoic

○ Should not be confused with increased splenic FDGuptake in setting of hematopoietic stimulating agents or

in immediate post-therapy setting

○ High-grade lymphomas (Burkitt, diffuse large B-cell,anaplastic, grade III follicular, nodular sclerosing HD) tend

to have greater FDG uptake than low-grade lymphomas

○ CECTDIFFERENTIAL DIAGNOSIS

• Multiple different primary splenic tumors (hemangioma,

lymphangioma, hamartoma, etc.), most of which havenonspecific imaging appearance

• Degree of concern (and need for biopsy/splenectomy)

should be based on clinical scenario and suspicious imagingfeatures, but most primary splenic lesions are benign,incidental findings

Splenic Infarction

• Wedge-shaped peripheral hypodense defect that does

not appear mass-like

• May be pyogenic, parasitic, fungal (microabscesses), or due

to tuberculosis

• Pyogenic abscess typically appears as low-density lesion

with thick, irregular enhancing wall

• Fungal (e.g., Candida, Aspergillus, Cryptococcus) abscesses

usually present as multiple, small, low-density lesions

Sarcoidosis

• Hepatosplenomegaly with multiple, variably sized,

hypodense nodules in liver and spleen

• Often associated with upper abdominal lymphadenopathy

• Presence of characteristic interstitial lung changes and

mediastinal/hilar adenopathy can be clue to diagnosis

Artifact

• Heterogeneous splenic enhancement ("moire" pattern) in

arterial phase could theoretically mimic splenic tumorPATHOLOGY

General Features

• Etiology

○ Splenic metastases: Multiple potential primarymalignancies may metastasize to spleen– Usually seen in patients with widespread metastaticdisease

– Isolated splenic metastasis (i.e., metastasis to spleen inabsence of metastatic disease elsewhere) is

extraordinarily rare

□ Isolated splenic metastases most often due togynecologic malignancies

○ Splenic lymphoma– HD and NHL– Primary lymphoma (limited to spleen and usually NHL)much less common than secondary lymphomaCLINICAL ISSUES

Presentation

○ Splenic metastases– Most patients are asymptomatic– Symptoms may include LUQ pain, weight loss,palpable mass, or splenomegaly

– Acute pain symptoms may occur in setting of splenicinfarct due to tumor emboli/splenic vein thrombosis

or splenic rupture due to tumor growth (very rare)

○ Splenic lymphoma– Fever, weight loss, night sweats, malaise, LUQ pain,palpable mass, splenomegaly

• Chemotherapy for systemic disease

• Splenectomy for isolated splenic tumorDIAGNOSTIC CHECKLIST

• Splenic size not reliable indicator of presence or absence oflymphomatous involvement

• Isolated splenic lesion (in absence of metastatic diseaseelsewhere) is very unlikely to represent metastasisSELECTED REFERENCES

1 Thipphavong S et al: Nonneoplastic, benign, and malignant splenic diseases: cross-sectional imaging findings and rare disease entities AJR Am J Roentgenol 203(2):315-22, 2014

2 Caremani M et al: Focal splenic lesions: US findings J Ultrasound

16(2):65-74, 2013

3 Karlo CA et al: Computed tomography of the spleen: how to interpret the hypodense lesion Insights Imaging 4(1):65-76, 2013

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581

with non-Hodgkin lymphoma shows the spleen to be markedly enlarged with heterogeneous, hypoattenuating, discrete tumor foci ﬈ Note the lymphomatous infiltration in the adrenal gland ﬉ and nodes throughout the abdomen ﬊ (Right) Coronal

CECT in a patient with melanoma demonstrates innumerable metastases almost completely replacing the spleen, with an additional metastasis to the liver dome ﬅ.

(Left) Axial CECT

demonstrates a large, density splenic mass ﬈ found

low-to be a melanoma metastasis.

Melanoma is one of several tumors which can appear cystic, as in this case, and be misinterpreted as a splenic abscess (Right) Axial CECT in

a patient with metastatic ovarian carcinoma shows loculated ascites or cystic peritoneal metastases that indent the surface of the liver

ﬅ and spleen ﬇ Some of the metastases are within the splenic parenchyma.

with breast cancer shows a splenic metastasis ﬈ Several liver metastases were also present (not shown) In most published reports, breast cancer is the most common primary source for splenic metastases (Right) Axial

CECT shows a hypervascular mass ﬈ within the spleen that proved to be a metastatic focus from a gastric carcinoid tumor Tumors arising from the tail of the pancreas or other LUQ organs should also

be considered in the differential diagnosis for splenic tumors.

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SECTION 9

Liver

Introduction and Overview

Imaging Approach to the Liver 584

Congenital

Congenital Hepatic Fibrosis 590

AD Polycystic Liver Disease 594 Congenital Absence of Hepatic Segments 598

Infection

Hepatic Pyogenic Abscess 600 Hepatic TB and Fungal Infections 604 Hepatic Amebic Abscess 608 Hepatic Hydatid Cyst 612 Hepatic Schistosomiasis 616 Viral Hepatitis 620

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Alcoholic Liver Disease 626 Autoimmune Hepatitis 630 Steatosis and Steatohepatitis 632 Hepatic Injury From Toxins 638

Primary Biliary Cirrhosis 652 )RFDO&RQƮXHQW)LEURVLV 658 Nodular Regenerative Hyperplasia 662 Regenerative and Dysplastic Nodules 668 Solitary Necrotic Nodule 676 Peribiliary Cysts 677

Metabolic or Inherited

Glycogen Storage Disease 678 Hemochromatosis 680 Wilson Disease 684

Degenerative

Hepatomegaly 688

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