Hyperdense renal masses: a computed tomographic dilemma.

High-density renal masses are atypical lesions that represent a diagnostic dilemma for computed tomography (CT). The differential diagnosis includes mainly complicated benign cysts and malignant neoplasms. This report analyzes the CT findings in 17 cases of discrete, sharply marginated masses that initially exceeded the density of the uninvolved renal parenchyma, averaging 50 H or more. The subsequently proven pathologic entities responsible for these high attenuation values included primary malignancies in six patients, one of whom also had multiple retention cysts containing highly proteinaceous, gelatinous material; a hemorrhagic cysts with an associated desmoplastic, fibrotic reaction in one patient; and single or multiple hemorrhagic cysts in four patients. No histologic proof was obtained in six patients, three with neoplastic disease and one mentally retarded youth who underwent renal aspiration without sufficient material obtained for analysis. Two patients with presumed hemorrhagic cysts have had serial CT scans without interval change in 8-12 months. An approach to the therapeutic management of affected patients is described.