Magnetic Resonance Cholangiopancreatography-Techniques and Applications

TECHNIQUE Conventional Techniques for Imaging Pancreaticobiliary System The basic technique of MRCP for evaluating the biliary tree uses heavily T2 weighted sequences, because bile has a

Cholangiopa ncreatography :

Tech niq ues and Applications

Sudha A Anupindi,MDa,b,*,Teresa Victoria,MDa,b

The imaging techniques currently advocated for

the evaluation of pancreatic and biliary diseases

in children include sonography, hepatobiliary

scin-tigraphy, CT and magnetic resonance

cholan-giopancreatography (MRCP) Imaging of the

pancreas and biliary system often requires a

combi-nation of two or more of these modalities to reach

an accurate diagnosis Among these techniques,

ultrasonography (US) remains the screening

exam-ination of choice in a child of any age presenting

with symptoms suggesting a primary

pancreatico-biliary process US can provide a rapid assessment

of biliary tree and pancreas, but it may be limited in

providing anatomic detail in certain areas, and it

cannot provide functional information

Hepatobili-ary scintigraphy offers physiologic information,

but it lacks anatomic detail CT is the first line of

im-aging in adults who have pancreatic diseases,

es-pecially pancreatic masses With the concerns of

ionizing radiation, however, CT is used cautiously

for evaluating pancreaticobiliary abnormalities in

children, with the exception of evaluation of acute

trauma, complications of pancreatitis, and

postsur-gical findings Although once the reference

stan-dard for depicting biliary pathology, endoscopic

retrograde cholangiography (ERCP) is not used

often for diagnosis because of radiation exposure

It has evolved to be mainly a therapeutic option

MRCP has emerged as a fast, safe, accurate,

noninvasive alternative to ERCP for evaluating

the biliary system in children It depicts

simulta-neously the biliary tree and pancreatic

paren-chyma without using ionizing radiation or

contrast agents Since its introduction in 1991, MRCP has become an invaluable tool in the imag-ing evaluation of the biliary system This article reviews MRCP techniques and their applications for assessing anatomic biliary and pancreatic variants and common pediatric diseases

TECHNIQUE

Conventional Techniques for Imaging Pancreaticobiliary System

The basic technique of MRCP for evaluating the biliary tree uses heavily T2 weighted sequences, because bile has a high water content and ap-pears bright on these sequences with its long T2 relaxation times, in contradistinction to the sur-rounding solid organs, which are relatively dark.1,2

The conventional protocols for MRCP include thick-slab T2 weighted turbo spin echo (TSE) and half-Fourier acquisition single-shot turbo spin echo (HASTE) in the coronal, coronal obli-que, and axial planes

Heavily T2 weighted sequences can be acquired

in a single thick slab (30 to 80 mm thickness) in any plane and can be performed without postprocess-ing techniques The advantage of multiplanar im-aging, particularly in coronal and oblique planes,

is improved visualization of overlapping fluid structures.3–6 The advantage of HASTE is the acquisition of thin slices (3 to 4 mm) rapidly with minimum patient motion

If a patient is sedated or cannot breath-hold, these sequences can be performed with a

Department of Radiology, The Children’s Hospital of Philadelphia, 34th Street and Civic Center Boulevard,

Philadelphia, PA 19104, USA

* Corresponding author Department of Radiology, The Children’s Hospital of Philadelphia, 34th Street and

Civic Center Boulevard, Philadelphia, PA 19104.

E-mail address: anupindi@email.chop.edu (S.A Anupindi).

KEYWORDS

 Magnetic resonance cholangiopancreatography

 Children  Biliary disease  Pancreas  3 T  1.5 T

Magn Reson Imaging Clin N Am 16 (2008) 453–466

doi:10.1016/j.mric.2008.04.005

respiratory triggering Acquisition of both thick

col-limation slab and thin colcol-limation multislice images

complement each other in the visualization of the

biliary tree The thick slab image should be

inter-preted in conjunction with the thin slab axial and

coronal images to avoid artifact from volume

averaging

Conventional unenhanced T1 and T2 weighted

imaging also is performed routinely for evaluating

the pancreaticobiliary system T1 and T2weighted

images are necessary to assess extrahepatic

causes of biliary obstruction and the liver

parenchyma

Patient Preparation Before Scanning

Four hours before the study, the patient should have

nothing by mouth (NPO) to decrease bowel motion

Bowel paralytic agents are not used in the authors’

institution, nor have recent publications

recommen-ded this as part of their protocol Negative oral

con-trast agents that have superparamagnetic effects

may improve the visualization of the biliary ducts

by nulling the inherent high signal of gastric juices

in the stomach and duodenum Commercially

avail-able negative oral contrast agents, such as

feru-moxsil (Gastromark, Mallinckrodt, St Louis, MO),

use the iron content to produce dark signal in the

bowel.6More palatable and less expensive

alterna-tives, however, include pineapple or blueberry

juice, which have high manganese content and

have similar darkening effect on MR imaging.7

Coil selection is critical and depends on the

pa-tient size The smallest possible coil that covers

a body part of interest should be used to ensure

high signal-to-noise (SNR) and improve spatial

resolution

Contrast Agents

MR images of the biliary system and pancreas are

obtained routinely with conventional gadolinium

chelate agents Gadolinium-enhanced T1 weighted

images with fat saturation are helpful when

evaluat-ing hepatic parenchymal disease before and after

liver transplant or neoplastic processes affecting

the liver and bile ducts Delayed scanning 10 to

20 minutes after the intravenous administration of

contrast agents results in bile becoming

hyperin-tense.8–10Conventional gadolinium chelates used

presently are excreted renally and offer limited

assessment of the biliary system and function

On the other hand, newer contrast agents, such

as manganese derivatives, mangafodipir trisodium

(Teslascan, Amersham Biosciences, GE

Health-care Technologies, Chalfont, St Giles, United

Kingdom); improved gadolinium chelates, such

as gadobenate dimeglumine (Multihance, Bracco,

Milan, Italy); and gadolinium-ethoxybenzyl-diethylene-triamine-penta-acetic acid (Gd-EOB-DPTA), which are taken up by the hepatocytes and excreted into the biliary system, have the potential to improve visualization of the hepatobili-ary system.4,11They have rigorous protocols and delivery systems, however, which limit their use

in pediatric populations Teslascan is no longer available in the United States.5

Advanced Techniques: 3 T MR Imaging Advanced techniques that improve SNR and de-crease acquisition time include three-dimensional T2 weighted TSE techniques and imaging with 3T scanners.4,5,12 Maximum and minimum intensity projections reconstructed from three-dimensional T2 sequences performed with parallel acquisition technique allow for higher SNR, thinner slices without gaps, and overall improved anatomic ac-curacy.4The advantage of this technique in chil-dren is more diagnostic information with less scan time This is extremely beneficial from a seda-tion viewpoint Three-dimensional sequences can

be performed with both 1.5 T and 3 T magnets

In addition, techniques such as VERSE (variable-rate selective excitation) and SPACE (sampling perfection with application optimized contrasts using different flip angle evolution) have been introduced in the last 2 years for MRCP on both 1.5 T and 3 T equipment.4,5 The goal of these sequences, in conjunction with parallel imaging,

is again to shorten scan times and improve SNR and spatial resolution

The technical parameters for 3 T and 1.5 T scan-ners differ and need to be optimized for each scanner A 3 T magnet has more inherent T1 char-acteristics Thus, the repetition time, flip angle, and inversion time need to be selected to achieve the desired signal in the tissue examined T2 is virtually unchanged or perhaps slightly decreased with an increase in magnetic field strength.13

Several publications have described the follow-ing advantages with 3 T imagfollow-ing:

Superior visualization of the cystic duct and common bile duct (CBD) using HASTE and three-dimensional TSE sequences Increased sensitivity and specificity in the detection of intrahepatic ductal variants Improvement in radiologist’s confidence level

in diagnosis Improved visualization of nondilated ducts6

This last point is important in children, because often they have very small nondilated ducts The existing data, however, do not show that the pancreatic duct is evaluated better at 3 T than at

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1.5 T imaging.6The disadvantages of 3 T imaging

include greater susceptibility artifacts At the

pres-ent time, there are no dedicated studies

compar-ing MRCP at 3 T versus 1.5 T in children 3 T MRCP

imaging is promising for improving SNR and

contrast-to-noise ratio

Pitfalls in Diagnosis at Magnetic Resonance

Cholangiopancreatography

A major limitation of MRCP in children is the small

size of the peripheral ducts, which can result in

false-negative studies The use of both secretin

(Figs 1 and 2) and morphine sulfate has been

described to overcome this obstacle Secretin is

a hormone that stimulates the exocrine pancreas

to secrete fluid and bicarbonate, resulting in a tran-sient increase in pancreatic fluid volume that then distends the pancreatic duct.14,15A negative oral contrast may be administered also to suppress the signal of the stomach and duodenum, which otherwise may interfere with the signal of the biliary duct Fukukura and Fujiyoshi14 reported visualization of the main pancreatic duct in the head, body, accessory pancreatic duct, and branch duct before the administration of secretin

in 94%, 84%, 9%, and 1%, respectively Following the administration of secretin, each segment of the pancreas was visualized in 100%, 98%, 42%, and 18% respectively, allowing for a better evaluation

administration of secretin Images at 4 (B) and 10 (C) minutes following the administration of the hormone show

improved visualization of the pancreatic duct and excretion of pancreatic juices into the duodenum (Courtesy of

Ivan Pedrosa, MD, Boston, MA).

of the smaller ducts Another publication has

shown improved visualization of intraductal filling

defects and ductal narrowing by overdistending

the ducts with secretin.16 This finding was less

apparent in patients with chronic pancreatitis

who already had chronically dilated ducts These

authors also demonstrated that congenital

vari-ants, such as pancreas divisum and associated

anomalies including santoriniceles (a cystic

dilata-tion of the dorsal duct just proximal to the minor

papilla), were more evident after the administration

of secretin.17The use of secretin in the pediatric

population has been shown to be safe and to

significantly enhance visualization of the

pancre-atic duct.6The drawback of secretin

administra-tion includes the cost of the hormone and the

increased MR imaging scan time Its use,

how-ever, may obviate invasive procedures like ERCP

Morphine sulfate, which is an opioid analgesic,

also has been used to improve ductal visualization

Morphine increases the contraction of the

sphinc-ter of Oddi, resulting in an increase in the resting

biliary pressure and distension of the biliary and

pancreatic ducts Silva and Friese18 have

described the use of morphine during MRCP in

adults to improve the visualization of small

intrahe-patic biliary and cystic ducts, and the main

pan-creatic duct A slow intravenous injection (over 1

to 2 minutes) of 0.04 mg/kg of morphine sulfate

was given with a scan delay time of 10 to 20

min-utes.18The use of morphine appeared to be

partic-ularly helpful when evaluating the biliary anatomy

before transplant However, at this time, there

are no clear indications or published experience

regarding the use of morphine enhanced MRCP

in children

Artifacts Artifacts can be classified as motion-related, tech-nical, or miscellaneous

Motion artifacts Artifacts secondary to motion are the result of tis-sue movement during the acquisition of the data and are categorized as voluntary or involuntary.19

A key element in optimizing MRCP is suppression

of voluntary patient motion Voluntary motion is often the result of anxiety and claustrophobia, re-sulting in gross motion degrading the images Pro-cedural sedation can minimize voluntary motion, and patients should be screened carefully before imaging to determine the need for sedation Usu-ally children over 8 years of age can cooperate successfully for MRCP after explanation of the procedure and reassurance by the parents In the authors’ experience, procedural sedation is essential for children younger than 8 years It is also helpful to ensure that the patient is in a com-fortable position and has an empty bladder Pro-cedural sedation requires monitoring and can be achieved best using several agents, including but not limited to intravenous fentanyl citrate, versed, pentobarbital sodium, ketamine, and propofol.20

A complete discussion of the protocols for seda-tion is beyond the scope of this article, as they vary with institutional policies

Involuntary motion-related artifacts result from breathing, motion from adjacent structures, such

secretin, there is limited visualization of the pancreatic duct (arrows), particularly distally A possible cyst is present at the level of the pancreatic head (arrowhead) (B) Four minutes after administration of secretin, there is better visu-alization of the pancreatic duct, which drains into the minor ampulla (arrow) Communication of the dorsal duct with the cystic lesion is now evident In addition, a small ventral duct now is seen draining into the major ampulla (arrowhead) with no evidence of communication with the dorsal duct (Courtesy of Ivan Pedrosa, MD, Boston, MA.) Anupindi & Victoria

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as bowel, and pulsation artifacts from vessels.

Respiratory triggering can minimize

respiratory-related artifacts Respiratory motion artifact also

may result in misregistration of the ducts, which

can appear discontinuous or stenotic on maximal

intensity projection (MIP) sequences Careful

interpretation of the source images or use of

single-section sequences may help avoid these

problems Keeping the patient NPO to the study

can help reduce bowel peristalsis

Technical-related artifacts

The disadvantage of conventional MRCP

tech-niques, SSFSE, and HASTE is low signal-to-noise

at the expense of resolution, which can impair

visualization of small intrahepatic biliary

radi-cals.4,21–23 The disadvantage of the thick-slab

technique is impaired visualization of small

intra-ductal filling defects because of volume averaging

The limited number of projections with slab

tech-niques also means that anatomic detail may be

delineated poorly

Overestimation of ductal narrowing may occur

in MRCP when compared with ERCP.24 During

ERCP, the ducts are overdistended because of

the relatively high pressure injection of contrast

In MRCP, the ducts are imaged in the in vivo state,

sometimes artificially suggesting focal stenosis or

narrowing A normal duct distal to area of

narrow-ing suggests that narrowed area is in fact an

arti-fact rather than a true finding

MRCP imaging at 3 T also has brought new

challenges with regard to artifacts Radio

fre-quency (RF) inhomogeneity is one of the greatest

challenges of 3 T imaging.5 The physics behind

this artifact are beyond the scope of this article

Suffice it to say that constructive or destructive

interference from standing RF waves results in an

area of brightening and darkening, respectively.13

The larger the field of view, such as in obese

pa-tients, the more pronounced the artifact A related

artifact occurs with electrical current interference

in a highly conductive medium like ascites,

result-ing in focal signal dropout Chemical shift artifact is

also more apparent at 3 T imaging This artifact is

caused by difference between the RF of protons in

water and fat, resulting in misregistration artifact

only seen along the frequency-encoding axes

This may be overcome by use of saturation pulses

to null the signal of fat, or by swapping the

fre-quency and phase-encoding direction.13

Miscellaneous artifacts

Blood products, gas, and other debris in the bile

ducts can decrease the signal intensity of bile

and create pseudo lesions leading to false-positive

results.4 Metallic artifacts from surgical clips or

stents can also result in signal void and obscura-tion of pathology.23 The use of spin echo se-quences instead of gradient echo, and avoidance

of fat-suppressed sequences helps to decrease these artifacts

Another artifact on MRCP is a pseudolesion re-lated to adjacent arteries causing a flow artifact in

a duct-mimicking stones.23Such flow-related arti-facts can be seen on MIPs, and a thorough evalu-ation of source images can overcome this pitfall

The presence of iodinated material in the biliary tract from prior ERCP can appear as low signal intensity filling defect on heavily T2 weighted sequences, simulating pathology MRCP should not be obtained immediately after ERCP.23A plain abdominal radiograph may aid in evaluating resid-ual contrast in the biliary tree before obtaining an MRCP

NORMAL ANATOMY AND VARIANTS

By the fourth week of gestation, ventral and dorsal pouches develop at the junction of the foregut and the midgut (Fig 3) The ventral bud (or hepatic di-verticulum) develops into the liver, gallbladder, ducts, and ventral aspect of the pancreas and their accompanying bile ducts, whereas the dorsal bud gives rise to the dorsal pancreas At about week 7

of gestation, the dorsal and ventral anlagen of the pancreas fuse, and their ducts unite

The main pancreatic duct is formed from the ventral duct and the distal aspect of the dorsal bud, draining in most cases through the major papilla into the duodenum The portion of pancre-atic duct extending from the ampulla to the site of anastomosis of the dorsal and ventral pancreatic anlagen is referred to as the duct of Wirsung If

a segment of the dorsal duct persists distal to the site of developmental anastomosis, this duct

is termed the Santorini or accessory duct The cal-iber of the pancreatic duct increases slightly from the tail to the head of the pancreas In its course, the duct receives about 25 tributaries, which insert into the duct at right angles.25,26These usually are not seen at MRCP unless they are pathologically or iatrogenically (by means of secretin) distended

In 91% of the population, the main drainage route for the pancreas is through the duct of Wirsung, which joins the CBD at the major ampulla The accessory pancreatic duct or duct of Santorini may be present in up to 44% of the population and may drain through the minor papilla, located about 2 cm cephalad from the major papilla.27

The ducts of Wirsung and Santorini can be seen

on MRCP

The right hepatic duct divides into anterior and posterior portions, which then join proximally

The right hepatic duct, which is usually shorter than

the left, joins the left hepatic duct, and together

they form the common hepatic duct (CHD) The

cystic duct inserts into the CHD usually below the

confluence of the right and left hepatic ducts to

form the CBD The CBD should measure less

than 1 mm in neonates, less than 2 mm in infants

up to 1 year of age, and less than 4 mm in older

children and adults In the postcholycystectomy

patient, the CBD may measure up to 1 cm.25,26

Knowledge of normal congenital variants is

important for surgical planning Variants of the

pancreatic system include an anomalous

pancrea-ticobiliary junction, which has a prevalence of

1.5% to 3.2% of the population.26,28In this variant,

there is fusion of the pancreatic duct and CBD

out-side of the wall of the duodenum, forming a

com-mon channel that measures more than 1.5 cm in

length The junction is distal to the sphincter of

Oddi, allowing reflux of the pancreatic juices into

the CBD This finding has been associated with

the formation of type 1 choledochal cyst, perhaps

because of the weakening of the ductal wall by

pancreatic enzymes, and with an increased inci-dence of pancreatitis, thought to be related to retrograde reflux of pancreatic juices into the anomalous duct Other pancreatic ductal variants include a dominant duct of Santorini and a variant called ansa pancreatica, in which the pancreatic duct forms a small loop at the embryologic site

of anastomosis between the ventral and the dorsal duct.25There are also numerous variations of the cystic duct that can contribute to biliary injury at surgery.29

CONGENITAL PANCREATIC ANOMALIES

Pancreas Divisum

In 6% to 8% of individuals, the ventral and dorsal pancreatic anlagens fail to fuse, resulting in a lon-ger dorsal duct that drains by means of the minor ampulla, and a shorter, ventral duct that drains into the major ampulla, a congenital anomaly called pancreas divisum (Fig 4) Its significance is that the dorsal duct may not accommodate the flow

of pancreatic secretions through the minor papilla

tree arise from the hepatic diverticulum while the dorsal pancreatic bud arises from the dorsal mesogastrium (C, D) After clockwise rotation, the dorsal and ventral pancreatic anlagens fuse The main pancreatic duct drains

by means of the ventral duct into the major papilla, while the dorsal duct drains the accessory pancreatic ducts through the minor papilla.

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It is equivocal whether this entity truly causes

pan-creatitis MRCP and secretin-enhanced MRCP are

highly sensitive and specific in detecting pancreas

divisum,2,6,17,30as illustrated inFig 2

Annular Pancreas

Annular pancreas is the second most common

congenital anomaly of the pancreas, after

pancre-atic divisum It may occur as an isolated finding, or

it can be associated with other congenital

anoma-lies including tracheoesophageal fistula, duodenal

atresia or stenosis, esophageal atresia, and Down

syndrome In this anomaly, which occurs at a rate

of 1 of every 2000 births, the pancreatic tissue

completely or partially encircles the second part

of the duodenum, resulting in gastric outlet

ob-struction If the tissue completely surrounds the

pancreas, the obstruction is complete, and the

patient usually presents at infancy If there is

par-tial encirclement, the patient may become

symp-tomatic later in life, or the finding may be

detected incidentally on imaging studies

Embryo-logically, annular pancreas is thought to be caused

by a bifid ventral anlagen, which surrounds the

duodenum and then fuses with the dorsal

pancre-atic portion forming a ring around the

duode-num.26 On MR imaging, an annular pancreas

appears as high signal tissue on fat-suppressed

T1 weighted sequences, completely or partially

encircling the duodenum.6

Pancreas Agenesis or Hypoplasia Total pancreas agenesis is extremely rare and virtually incompatible with life Partial agenesis of the pancreas is usually caused by agenesis of the dorsal or ventral pancreatic anlage Dorsal agenesis is more common than ventral agenesis

Patients may present with abdominal pain caused

by pancreatitis or with diabetes mellitus from an insufficient excretion of insulin On imaging, dorsal agenesis may present as a foreshortened pan-creas, or in the most extreme form, it appears as

a rounded pancreatic head with nonvisualization

of the remaining pancreatic tissue.26

CONGENITAL BILIARY ANOMALIES

Biliary Atresia Biliary atresia is thought to be the sequela of a de-structive inflammatory process leading to ductal fibrosis.31It may be focal, intrahepatic, or extrahe-patic The focal and intrahepatic types are ex-tremely rare and thought to be caused by an intrauterine vascular insult The most common form is extrahepatic atresia (Fig 5)

Extrahepatic biliary atresia usually becomes symptomatic in the first days or months of life as jaundice Prompt diagnosis is imperative, as the prognosis decreases proportionally with increas-ing age Several studies have evaluated the utility

of MRCP evaluating the biliary ducts in infants.32

MRCP may be useful when findings on sonogra-phy and nuclear scintigrasonogra-phy are equivocal Find-ings of biliary atresia on MRCP include periportal thickening, which represents fibrosis, and a small gallbladder Guibaud and Lachaud32 have re-ported that if the extrahepatic bile ducts are nor-mal in appearance on MRCP, then biliary atresia can be excluded In clinical practice, however, biopsy still is performed routinely to make the diagnosis of biliary atresia

Alagille Syndrome

In 1987, Alagille described the syndrome of arte-riohepatic dysplasia This syndrome has five major components: (1) abnormal facies (large forehead, small pointed chin, hypertelorism, poorly devel-oped nasal bridge), (2) chronic cholestasis, (3) oc-ular abnormalities, (4) butterfly vertebrae, and (5) pulmonary hypoplasia or stenosis Other less frequent features include growth and mental retar-dation, renal disturbances undertubulation, and osteopenia of bones and vascular malformations

The intrahepatic component of Alagille syndrome, which is characterized by paucity of the intrahe-patic ducts, may present during infancy or later

in life with cholestasis.33–35Liver biopsy in addition

pancreatitis Coronal maximal intensity projection

acquired from three-dimensional T2 weighted image

with SPACE (sampling perfection with application

optimized contrasts using different flip angle

evolu-tion) shows that the main pancreatic duct drains

into the minor papilla while the common bile duct

drains into the major papilla, findings diagnostic of

pancreas divisum.

Fig 6 Caroli syndrome Autosomal recessive kidney disease with congenital hepatic fibrosis (A) Coronal T2 weighted half-Fourier acquisition single-shot turbo spin echo (HASTE) image in this 5-year-old patient demon-strates moderate intra- and extrahepatic biliary ductal dilatation that tapers at the level of the proximal common bile duct (arrow) (B) Axial HASTE shows fine linear areas in the subcapsular region of the liver (arrowheads), which are hyperintense to liver, consistent with hepatic fibrosis.

single-shot turbo spin echo (HASTE) T2 weighted and (B) axial HASTE T2 weighted images demonstrate mild cystic dilatation of the common bile duct (CBD) (arrow) with tortuosity of the bile duct (arrowhead) At surgery, the CBD was found to be distended, terminating in a fibrous cord (C) Intraoperative cholangiogram Contrast was injected into the gallbladder and then passed into the intrahepatic ducts The extrahepatic duct fills only proximally (arrow) No contrast entered the small bowel, confirming the diagnosis of extrahepatic biliary atresia.

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to at least three of the previously mentioned

fea-tures provides the definite diagnosis The MR

imaging/MRCP hepatic findings of Alagille have

not been reported in the literature

Congenital Hepatic Fibrosis

Congenital hepatic fibrosis is a heritable,

develop-mental disorder characterized by the presence of

abnormal fibrous tissue in the portal tracts.34–36

Other associated biliary anomalies include biliary

cysts, Caroli disease, and choledochal cysts In

most cases, hepatic fibrosis is associated with

other extrahepatic findings, including renal tubular

ectasia, polycystic kidney disease, renal dysplasia,

and nephronophthisis Many consider congenital

hepatic fibrosis and autosomal recessive

polycys-tic disease in the same spectrum.36Dilated biliary

ducts and portal hypertension may lead to serious

complications, namely gastrointestinal

hemor-rhage and cholangitis Although congenital hepatic

fibrosis is a histologic diagnosis, MR imaging can

provide a comprehensive assessment of the liver

and ducts and the degree of portal hypertension

demonstrates an enlarged, irregular common bile duct (arrow) (B) Coronal maximal intensity projection of a

re-spiratory-triggered T2 weighted three-dimensional fast spin echo image demonstrates mild extrahepatic

dilata-tion of the proximal common bile duct, which tapers abruptly distally (arrow), consistent with type 1 choledochal

cyst A second infant with prenatal diagnosis of mesenteric cyst (C) Transverse sonogram demonstrates large

cystic structure (arrow) in the region of the porta hepatis (D) Thick slab T2 weighted coronal oblique image

dem-onstrates fusiform dilatation of the common bile duct (arrow) with mild dilatation of the intrahepatic ducts of

the left lobe (E) Axial T2 weighted half-Fourier acquisition single-shot turbo spin echo sequence confirms the

same findings but more clearly depicts dilatation of the intrahepatic ducts (arrow).

weighted sequence demonstrates Todani type 3 chol-edochal cyst/choledochocele with localized cystic dila-tation of the duodenal portion of the common bile duct (arrow) with a windsock deformity distally.

and associated cystic renal disease Based on the

authors’ experience, the degree of ductal dilatation

on MRCP can be extensive (Fig 6)

Choledochal Cysts

Choledochal cysts are not uncommon and first

may be diagnosed on fetal imaging There are

five types based on the Todani classification

sys-tem, and all have been described well by

MRCP.21,25,26,37 Most of the cysts are type 1,

which is diffuse involvement of the CBD and

com-mon hepatic duct (Fig 7) Type 2 involves isolated

cysts that protrude exophytically from the CBD

Type 3 is choledochocele, which is a focal

dilatation of the intraduodenal portion of the CBD (Fig 8) Type 4A involves dilatation of the intra and extrahepatic ducts, while type 4B involves only extrahepatic ducts, and Type 5 (Caroli disease) involves only intrahepatic ducts (Fig 9) The literature has shown that MRCP is comparable

or superior to ERCP and conventional cholangiog-raphy for depicting these cysts.4

Inflammatory Diseases Pancreatitis and primary sclerosing cholangitis represent the most common inflammatory condi-tions in children requiring MRCP application

maximal intensity projection reconstructed from three-dimensional T2 weighted SPACE (sampling perfection with application optimized contrasts using different flip angle evolution) sequence and (B) axial half-Fourier acquisition single shot turbo spin echo T2 weighted image demonstrate marked dilatation of the extrahepatic bile duct (arrow) with moderate tortuosity and distension of the intrahepatic ducts (arrowheads).

maximal intensity projection of a T2 weighted three-dimensional fast spin echo image demonstrates an irregular and mildly distended pancreatic duct, sequela from several episodes of pancreatitis (arrow) (B) Axial fast imaging with steady state precession image reveals atrophy of the tail of the pancreas (arrowheads) Note branches emanating perpendicular from the pancreatic duct because of ductal ectasia.

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