Filling defects in pyelograms are produced most frequently by renal tumors that arise from either the parenchyma or the pelvis. However, it is not uncommon for cysts, tuberculosis, nonopaque calculi, abscesses, blood clots or air bubbles to produce a roentgenological picture not unlike that of renal neoplasms. The urologist is aided materially in the diagnosis by the clinical picture, physical examination and laboratory tests.
Extrarenal diseases rarely produce pyelographic deformities. Perinephric abscesses, lipomas and retroperitoneal neoplasms occasionally produce abnormalities in the pyelogram either by invasion of or by pressure on the renal pelvis. Because of the close relationship of the surrounding viscera, it is theoretically possible for disease processes of the neighboring structures to produce pressure on the kidney and a filling defect in the pyelogram. Stone summarized nine cases of pancreatic cysts that simulated renal disease, one of which he observed personally. A report follows of a case in