Evaluation of ureteral obstruction by early intravenous pyelography

Acute ureteral obstruction was studied in dogs by intravenous pyelography at two, four, six, nine, 12, 24, 48 and 168 hours after total occlusion of the ureter. Ureteral obstruction was correctly diagnosed in all instances, if intravenous pyelography was performed within nine hours from the time of obstruction and if a two hour sequence roentgenogram was obtained. A variably diagnostic rate of 36 to 75 per cent occurred when intravenous pyelography was delayed until 12 hours or later. In ureters with a positive diagnosis, 65 per cent were correctly identified on the 15 minute film, 98 per cent on the one hour film and 100 per cent on the two hour film. Intravenous pyelography should be performed immediately after the onset of renal insufficiency to obtain maximal information, as deterioration in renal function from total ureteral obstruction rapidly causes inadequate excretion and concentration of contrast material and prevents visualization of an obstructed collecting system.