Solution to Unknown Case #5 – Calyceal Diverticulum

History: 16 year old female with recurrent flank pain. 

Calyceal diverticulum: prone image from an intravenous pyelogram 25 minutes after intravenous iodine contrast injection reveals a small pooling of contrast in an upper pole calyx in the right kidney (yellow arrows) connected by a narrow channel to the renal pelvis, compatible with a calyceal diverticulum.

Calyceal diverticulum: Coronal CT of the abdomen and pelvis with contrast reveals a small outpouching in an upper pole calyx of the right kidney (yellow arrows), compatible with a calyceal diverticulum.

This is the appearance of a calyceal diverticulum, which is a small outpouching or eventration of a calyx into the renal parenchyma. They are usually connected by a narrow channel to the renal pelvis, as seen in the IVP image above. A calyceal diverticulum can be complicated by renal colic (renal stone), which was the cause of recurrent flank pain in this patient. Occasionally, milk of calcium can precipitate or layer within the calyceal diverticulum and mimic a renal stone. Most commonly, a calyceal diverticulum is incidentally discovered as they are typically asymptomatic.