Milk of calcium in renal cysts: new sonographic features.

Milk of calcium (MOC) in a small renal cyst or calyceal diverticulum is quite common. Ninety-one small renal cysts with MOC in 61 patients were found within a period of 4 years and 7 months. The main sonographic features are echogenic material layering in the dependent portion of a cyst, associated with reverberation echoes without shadowing. Shadowing was seen when MOC was present in larger amounts. Because MOC is usually asymptomatic and requires no treatment, differentiation from other lesions such as calculi or angiomyolipomas is important for proper patient management. MOC is detected more readily by ultrasonography than by radiography or CT.