We evaluated 25 patients undergoing urinary diversion with a nonrefluxing colonic conduit. Renal scarring developed in 10% of the kidneys during a median followup of 12.7 years. In 11 renal units (22%) deterioration of the ureteroenteric anastomosis occurred due to the development of reflux or stricture. Of these kidneys 45% had scarring; no renal unit in which the anastomosis remained intact had renal scars (p less than 0.001). Of our patients 96% had bacterial colonization of the colonic conduit but this was not associated with renal scarring if the urinary diversion was anatomically intact.