Internal Medicine

0521779407-18 CUNY1086/Karliner 0 521 77940 7 June 13, 2007 8:1

1286 Renal Masses and Tumors

■Presence of fat within a solid lesion is virtually diagnostic of angiomy-

olipoma

Cystic Renal Masses

■Vast majority of renal masses are simple cysts

■Incidence of simple renal cysts: 25–33% among patients >50 years of

age

■Renal ultrasound can definitively diagnose a simple cyst:

■Criteria: anechoic, through transmission, smooth-walled, without

solid components or calcifications.

➣Percutaneous cyst puncture generally not helpful in differentiat-

ing “benign” from malignant cysts

➣Bloody fluid or high protein content is not diagnostic

Cyst Classification (Bosniak System)

■Based on CT Criteria

■Accurate delineation requires:

■Pre- and post- contrast CT images with 5-mm cuts

Type I Cyst

■Simple cyst

■Smooth uncalcified walls, sonographic through-transmission,

■Uncomplicated simple cysts are definitively diagnosed by sonogra-

phy and/or CT, and are uniformly benign

Type II Cyst

■Minimally complicated cysts – are benign but have some radio-

graphic features of concern, including:

■Septated cysts, minimally calcified cysts, infected cysts, and high-

density cysts

■< 20% incidence of malignancy

Type II Hyperdense Cyst

■Smooth, round, sharply marginated, homogenous lesion

■Does not enhance, configuration remains unchanged after IV con-

trast

■3 cm or less

Type III Cyst

■More complicated cystic lesions that cannot be confidently be dis-

tinguished from malignancy on radiographic imaging

■Should be surgically explored unless clinically contraindicated

■Incidence of malignancy: 30–60%