Radiological Evaluation of Renal Masses by Dr. Jeffrey Wong

Radiological Evaluation of Renal Masses

Renal Mass: Overview

Imaging Armamentarium

sensitivity of IVP is limited in detecting small renal lesions, and overall, fails to detect 1/5 to 1/3 of renal masses smaller than 3 cm
determining whether a renal mass is benign or malignant requires US or CT

Radiological Analysis of Renal Lesions

differential diagnosis of mass like lesions: pseudotumors(persistent fetal lobations, columns of Bertin, anomalies, or hypertrophied parenchyma), cysts, inflammatory lesions, and neoplasia
bronchogenic carcinoma is the most common tumor to metastasize to the kidney
CT scan with and without contrast remains the gold standard for characterization of renal masses
CT allows attenuation before and after contrast, margin with the surrounding kidney, presence and type of calcifications, presence and type of cyst wall or septation
fat has less than 0 Hounsefield units-diagnostic of hamartoma(AML)

Cystic Renal Lesions

Bosniak classification of cystic lesions is based on CT findings
Category I-benign simple cysts: anechoic, sharply marginated, smooth walls, low attenuation(0-20 HU)
Category II-mildly complicated cysts: thin septa, small amount of border forming calcifications
include “hyperdense cysts”: small(<3cm) nonenhancing, homogenously hyperdense(40-90HU) cysts with smooth walls
Category III-inderterminate:
Category IV-malignant: noninflammatory cystic lesions with definite solid features, such as irregularly thick margins, thickened septa, wall nodularity, large or nonborder forming calcification and/or equivocal enhancement
first two categories are benign and second two are malignant until proven otherwise
lesion enhances if a rise in attenuation of at least 10-20 HU

Ancillary Modalities

angiography rarely used because a negative angiogram does not exclude renal cancer
cyst puncture can occasionally provide useful data: infectious etiology can be ruled out, diagnostic accuracy rates can be as high as 99%
needle tract seeding is rare and is not considered a deterrent to cyst puncture

New Modalities

spiral CT:single continous XRAY exposure that is fast enough to be executed during a single breath hold
eliminate respiratory artifact
oncocytomas may constitute 10% or more of small(<3cm) solid neoplasms

Role of MRI

principle advantage is the identification of tumor-free vessels
gadolinium-DTPA is not nephrotoxic therefore can be used in renal failure patients

New