Incidental renal mass.

Fifty-five patients with 64 incidentally discovered renal masses were evaluated with sonography and/or computerized tomography (CT scanning). Cyst puncture or surgical exploration confirmed the nature of the mass in all cases. We demonstrate that ultrasound is accurate in evaluating renal mass lesions 3 cm. in size or greater, but cannot distinguish between simple or hemorrhagic cysts. CT scanning can characterize lesions 1.5 cm. or greater in size, and those masses that are clearly cystic by CT scanning do not require further evaluation. Masses found to be indeterminate or solid by CT scanning require a more traditional approach. A 9.1-per cent incidence of malignant tumors in this series emphasizes the need for a complete and meticulous evaluation of all renal masses.