CT of the renal cyst: is cyst aspiration necessary?

Fifty patients with a total of 56 renal masses discovered on routine excretory urography or abdominal plain films and with ultrasonographic diagnoses of definite or probable benign cysts underwent computed tomography (CT) prior to cyst aspiration with cytologic study. All lesions met strict criteria for the CT diagnosis of benign cyst and subsequently proved to be benign cysts. In addition, CT scanning detected 11 other renal masses, only one of which could be retrospectively diagnosed on the original urogram. It is suggested that renal cyst aspiration need not be performed when lesions meet all CT criteria for a benign cyst.