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

Prenatal diagnosis of hydronephrosis. Ultrasonography after delivery showed severe right hydroureteronephrosis with a very dilated and tortuous ureter seen just below the level of the kidney (figure 1) and behind the bladder (figure 2) VCUG was normal. IVP showed very severe hydronephrosis with marked dilatation of the renal pelvis and marked ureteral dilatation and tortuosity (figure 3) Calyceal crescents were seen on some of the earlier images (figure 4) The baby underwent excision of the distal segment and tapering and reimplantation of the right ureter (megaureter repair). The post-op IVP showed marked decrease in the degree of hydronephrosis. The pelvicalyceal system was almost normal in volume. The concentration of contrast material was markedly improved and the ureter returned to an almost normal calibre (figure 5)