High protein content: another cause of CT hyperdense benign renal cyst

A high density renal mass (35 Hounsfield units), which did not enhance after intravenous contrast material proved to be a renal cyst containing a very proteinaceous fluid. The high protein concentration was the apparent cause of the unusually high attenuation values observed. This case is discussed and the causes of hyperdense benign renal cysts on computed tomography are reviewed.