Impressions upon the ureters accounted for by extrinsic pressure defects exerted by adjacent or crossing arteries and veins are frequently noted on urographic studies. The observation of these extrinsic pressure defects is usually made, but their significance is often overlooked. We have discussed and illustrated those conditions which may result in ureteral notching on an arterial and venous basis.The arterial causes of ureteral impressions include:1. impressions by accessory but normal renal arteries;2. compression by a normal iliac artery;3. renal artery stenosis;4. aortic and iliac artery occlusion;5. cirsoid aneurysm of the renal artery;6. impression by aortic and hypogastric artery aneurysm.The venous impressions on the ureters may be due to:1. normal gonadal vein crossing defect on right or on left;2. right ovarian vein syndrome;3. varicocele and varices of the broad ligament;4. occlusion of the inferior vena cava below the level of the renal veins by tumor, clot, retroperitoneal fibrosis, or follo...