CT of carcinoma of the renal pelvis.

CT in 28 histologically proven carcinomas of the renal pelvis (pTa-2, n = 12; pT3-4, n = 16) in 26 patients was evaluated retrospectively. Twenty-four of 28 tumors could be identified at CT, 17/28 at urography, and 12/14 at retrograde pyelography. Nineteen tumors appeared as a discrete intrapelvic mass with an attenuation close to that of the kidney on noncontrast scans. There was slight to moderate enhancement of the tumors following i.v. contrast medium injection but they appeared hypodense relative to the renal parenchyma. Five tumors caused only a diffuse obliteration of the renal sinus. Criteria to define peripelvic tumor growth are proposed, i.e. tumors obliterating fat planes or abutting of renal parenchyma should not be regarded as signs of extrapelvic extension, while inhomogeneous attenuation of peripelvic fat and renal parenchyma (in the absence of other explanation) should, or if the tumor mass is seen interdigitizing with surrounding structures. Thickening of Gerota's fascia or septa in the perirenal space are unspecific findings. With CT we were able to differentiate tumors confined to the renal pelvic wall from those with more advanced disease including metastases in 22 of 26 patients.