Evaluation of renal masses considered indeterminate on computed tomography.

Of 815 renal masses studied by computed tomography (CT), 60 did not fit the criteria for cyst or neoplasm and thus were called indeterminate. When artifacts were present, the likely diagnosis was a simple cyst; when no artifacts were present to explain atypical features in cyst-like masses, further investigation was necessary. Angiography was useful in only 16%, while ultrasound combined with cyst aspiration was diagnostic in 84%. All solid lesions required surgical investigation. Ultrasound with or without aspiration is recommended for all cyst-like renal masses thought to be indeterminate on CT.