The nonopacified kidney with Wilms' tumor.

We reviewed 56 cases in which the preoperative diagnosis was Wilms' tumor at the Children's Hospital of Philadelphia (CHOP) during the three calendar years 1983 through 1985. Fifty-one had Wilms' tumor (38 operated on at CHOP; 13 were referrals for further treatment or consultation), three had renal cell carcinoma (RCC), and one each with metastatic mesoblastic nephroma and clear cell sarcoma. We reviewed these cases to determine the significance of the urographic finding of nonopacification of kidney with suspected Wilms' tumor, and what additional diagnostic studies are needed. Five Wilms' tumor patients (10%) and one RCC patient had nonopacification of the involved kidney on intravenous pyelography (IVP). Four Wilms' tumor patients had tumor extending into the collecting system: into the proximal ureter in one, obstructing the superior pole in another, and filling the renal pelvis in two, one of which also had tumor extending through the inferior vena cava and into the right atrium. One patient with Wilms' tumor and one with RCC had huge left-sided tumors that crossed the midline and appeared to replace completely the functioning renal parenchyma on that side. The most common cause of nonpacification of kidney by Wilms' tumor is collecting system blockage by tumor. Although extension into the renal pelvis is relatively uncommon in Wilms' tumor (five of 51 cases during the study period, 10%), when it occurs, nonopacification of IVP often results (four of five cases, 80%). Although renal vein involvement is more frequent (eight of 51 cases; 16%), nonopacification is unusual (one of eight cases, 13%; the tumor also had filled the collecting system).(ABSTRACT TRUNCATED AT 250 WORDS)