Figure 6a. Renal sinus cyst in a 54-year-old asymptomatic man. (a) Excretory urogram shows splaying of the calices and compression of the right renal pelvis (arrows), findings suggestive of a focal lesion. (b) Axial contrast-enhanced CT scan shows a single, well-defined, water-attenuation cyst (arrows) protruding into the renal sinus. It has the same appearance as the more common renal cortical cyst (arrowhead).