Answer
Delayed Excretory Phase Caused by Obstruction – CT
CT of the upper abdomen in axial projection shows a right kidney that is in the corticomedullary phase while the left kidney is already in the excretory phase with contrast noted in the intrarenal collecting system, This finding is known as a delayed excretory phase of the right kidney. This patient presented with acute flank pain and hematuria and was shown to have a stone in the distal right ureter at the UVJ.
Ashley Davidoff MD TheCommonVein.net 16015b