Renal cysts: curios and caveats.

Interesting, unusual, and confusing renal cysts from a group of 200 cysts punctured percutaneously during the past decade are presented. Some cases illustrate pressure phenomena in cysts adjacent to each other or causing calyceal obstruction. Also reported are cyst wall findings, unusual cyst configurations, infection in pre-existing cysts, examples of cysts simulating renal cell carcinoma, and renal cell carcinoma presenting as cysts. In unusual cases, percutaneous needle puncture remains the procedure of choice for establishing the diagnosis of benign simple cyst versus malignancy or infection, or for determining the relationship of a cyst with the collecting system or with other cysts. Cyst puncture may also result in iatrogenic changes.