What is the appearance of urinary tract obstruction on an IVU CTU and MRU?
Obstruction of the urinary tract causes delay in the development of a nephrogram in the affected kidney, a delay in contrast excretion, and dilation of the upstream collecting system. Long-standing severe obstruction can cause atrophy of the renal parenchyma and is referred to as hydronephrotic atrophy. Obstruction can be related to intrinsic causes in the collecting system or ureter, such as stones or urothelial tumors, while extrinsic obstruction is due to compression by lesions adjacent to the collecting system or ureter, such as metastatic tumors or retroperitoneal fibrosis. The cause of urinary obstruction is best evaluated on cross-sectional imaging studies such as CT or MRI.
