A calyceal diverticulum will appear similar to a renal cyst on early post-contrast CT images, although it may contain stones in the dependent part.

In the excretory phase, the cystic structure fills with contrast material due to communication with the collecting system, and the layering of contrast material is seen within. This helps differentiate the calyceal diverticulum from a renal cyst, which does not connect with the collecting system.