CT of the hyperdense renal cyst: sonographic correlation

The computed tomographic (CT) appearances of 19 hyperdense renal cysts in nine patients are reported. Sixteen of these cysts were found over a period of only 1 year with state-of-the-art CT equipment. A CT diagnosis of benign hyperdense renal cyst can be made if a lesion meets all of the following criteria: 1) smoothly outlined imperceptible wall with sharp demarcation from the kidney; 2) before intravenous contrast injection, homogeneous internal content with CT numbers 40-240% higher (70-240% higher for lesions 10 mm or more in diameter) than renal parenchyma; and 3) after intravenous contrast injection, persistent internal homgeneity and insignificant enchancement (less than 6%) relative to normal renal cortex. For masses exceeding 15 mm in diameter, sonography can be a valuable confirmatory test