Comprehensive evaluation of renal masses by CT requires a dedicated renal CT protocol.. In addition, the precontrast phase provides the low-est sensitivity for detecting renal masses.. A
Trang 1the corticomedullary, nephrographic, and excretory
phases, with little or no respiratory or
patient-motion artifacts[7] Multiphase imaging of the
kid-ney thus permits not only high-resolution imaging
of the renal parenchyma but also that of its
vascula-ture and collecting systems[8]
Comprehensive evaluation of renal masses by CT
requires a dedicated renal CT protocol The various
phases of CT imaging of the kidney include
pre-contrast, arterial (15–25 second delay),
corticome-dullary (35–80 second delay), nephrographic
(85–180 second delay) and excretory (3 minutes
or more) phases[7] Preliminary noncontrast scans
are used to detect calcifications and allow
quantifi-cation of enhancement on the postcontrast scans
However, unenhanced scans alone are inadequate
for lesion characterization because no information
exists regarding lesion vascularity/enhancement
In addition, the precontrast phase provides the
low-est sensitivity for detecting renal masses
During the corticomedullary phase (CMP), con-trast resides in the cortical capillaries, peritubular cells, proximal convoluted tubules, and columns
of Bertin [9] Optimal time delay for the CMP phase depends on the rate of injection, the amount
of contrast material administered, and the patient’s cardiac output Advantages of the CMP include the differentiation of normal variants of renal paren-chyma from renal masses and the better depiction
of tumor hypervascularity[10–12] Peak enhance-ment of renal vessels during early CMP also provides information on vascular anatomy and pa-tency[7,9] Two main disadvantages of the CMP are the difficulty in detecting small hypovascular lesions of the renal medulla (a low attenuation region during the CMP) (Fig 7) and detecting small hypervascular tumors of the cortex (a high attenuation region during the CMP) Small hyper-vascular cortical RCCs may enhance to the same de-gree as the normal cortex, whereas hypovascular tumors of the medulla may not enhance during this phase[9–13]
The nephrographic phase is obtained during the passage of contrast material through the renal tubu-lar system During the nephrographic phase, which usually begins 80 to 120 seconds after contrast injection, the renal parenchyma enhances homoge-neously Although the duration of the nephro-graphic phase is not clearly defined, for practical reasons it may be divided into an early phase and
a late phase, with the latter overlapping the excre-tory phase[7,9] The nephrographic phase is con-sidered the optimal phase for the detection and characterization of small renal masses [14] The excretory phase begins when contrast material is ex-creted into the collecting system, 3 to 5 minutes after contrast administration During this phase, the nephrogram remains homogeneous but its at-tenuation is diminished A summary of the phases
of renal enhancement for MDCT, including advan-tages and disadvanadvan-tages, is shown inTable 1
In many cases, the pattern of enhancement within a renal neoplasm is dense and irregular, and in such cases, subjective assessment for en-hancement is sufficient Even if enen-hancement is not particularly dense but is irregular or nodular within the mass, the mass is most likely neoplastic However, in some cases of hypovascular masses, enhancement may be more subtle and uniform
In such cases, it is useful to compare attenuation measurements between the precontrast and each
of the postcontrast phases Because enhancement
of the adjacent normal renal parenchyma results
in some degree of beam hardening, attenuation measurements often drift upward slightly, even in proven simple cysts This drift is more pronounced with smaller, predominantly intrarenal lesions,
Fig 5 AML with no detectable fat A soft tissue mass
(arrow) (M) is exophytic from the posterior aspect of
the right kidney (K) Although this finding was
path-ologically proved to be an AML, no fat was detected
at imaging, even on retrospective review.
Fig 6 Multiplanar reformation of the kidney
Isotro-pic scan acquisition and data reconstruction results in
multiplanar image quality comparable to the source
axial images In this case of multicentric RCC, the
dis-tribution of three renal masses (arrows) can be seen
on a single coronal image.
Cross-sectional Imaging Evaluation of Renal Masses 97
Trang 2Imaging of Hematuria
Owen J O’Connor, MD, MRCSIa,b,
Sean E McSweeney, MB, MRCSI, FFR(RCSI)a,b,
Michael M Maher, MD, FRCSI, FFR(RCSI), FRCRa,b,*
Hematuria may have a number of causes, the
more common being urinary tract calculi, urinary
tract infection (UTI), urinary tract neoplasms
(including renal cell carcinoma and urothelial
tu-mors), trauma to the urinary tract, and renal
paren-chymal disease[1–5] Hematuria is broadly divided
into macroscopic and microscopic varieties[6]
He-maturia is described as macroscopic or frank when
blood is visible within the urine[7,8] A diagnosis
of microscopic (occult) hematuria requires the
detection of three to five red cells per high powered
view, or greater than five red blood cells per 0.9
mm3of urine[5,9] The prevalence of microscopic
hematuria in asymptomatic individuals is
approxi-mately 2.5%[10]
Investigation of hematuria
The investigation of hematuria should begin with
a search for bacteruria or pyuria If either is present,
a urine culture should be ordered to confirm UTI
In the absence of infection, the next step is to distin-guish glomerular and nonglomerular sources of hematuria If the findings suggest a glomerular source of bleeding, no urologic evaluation is neces-sary, at least initially, and referral to a nephrologist
is indicated[11] Indeed, there is a body of opinion that suggests that patients aged less than 40 years and presenting with hematuria can be investigated initially by a nephrologist, as the risk of urologic malignancy is low[6] The results of a recent study
by Edwards and colleagues[6]support this policy
If a glomerular source is excluded in those with risk factors for urologic disease, urologic referral is advised[12] Risk factors include smoking history, occupational exposure to chemicals or dyes, history
of macroscopic hematuria, age greater than 40 years, previous urologic history, symptoms of irrita-tive voiding, UTIs, analgesic abuse, cyclophospha-mide intake, and history of pelvic irradiation
R A D I O L O G I C
C L I N I C S
O F N O R T H A M E R I C A
Radiol Clin N Am 46 (2008) 113–132
a Department of Radiology, Cork University Hospital, Wilton, Cork, Ireland
b Mercy University Hospital and University College Cork, Cork, Ireland
* Corresponding author Department of Radiology, Cork University Hospital, Wilton, Cork, Ireland.
E-mail address: m.maher@ucc.ie (M.M Maher).
- Investigation of hematuria
- Common urologic causes of hematuria
Urinary tract calculi
Malignancy
Macroscopic and microscopic hematuria and
prevalence of urologic disease
- Imaging of hematuria
Conventional radiography
Intravenous urography and excretion
urography
Retrograde pyelography
Ultrasound
- Multidetector CT urography
Indications for multidetector CT urography Imaging protocol
Image interpretation Current status of multidetector CT urography
in the evaluation of the patient with hematuria
How should we image the patient with hematuria in 2008?
- References
113
0033-8389/08/$ – see front matter ª 2008 Elsevier Inc All rights reserved doi:10.1016/j.rcl.2008.01.007 radiologic.theclinics.com