Robert L. Lebowitz, M.D. Children' s Hospital, Harvard Medical School Boston, Massachusetts

UPJ Obstruction with a Crossing Vessel

This 9 year-old boy had many years of intermittent right abdominal and flank pain. Finally, he was sent for ultrasonography of his abdomen, which showed severe right hydronephrosis (figure 1). A dilated ureter was not identified. An IVP was then performed. The preliminary film was normal. After the injection of contrast material, a film at 3 minutes (figure 2) showed a normal left kidney, but on the right there were prominent calyceal crescents, a urographic sign of chronic obstructive hydronephrosis. The crescents are due to concentrated contrast material in dilated, reoriented distal collecting ducts arranged around dilated calyces. In addition, "puddles" of contrast material are seen in the center of dilated calyces, surrounded by nonopaque urine.

A film at 90 minutes (figure 3) after injection showed typical findings for ureteropelvic junction obstruction of severe degree with very dilated calyces and pelvis. Of special interest was a small amount of contrast material in a nondilated proximal segment of ureter, just below the ureteropelvic junction. This appearance is very suggestive of extrinsic obstruction from a crossing lower pole renal vessel (see arrow). Extrinsic obstruction from a crossing lower pole renal artery was indeed found to be the cause of the obstruction at the time of surgery. The ureter was moved in front of the vessel and a dismembered pyeloplasty was performed. The hydronephrosis improved and the pain disappeared.

Right Kidney

3 Minutes

90 Minutes