Does hydronephrosis after extravesical ureteral reimplantation deteriorate renal function?

We analyzed whether newly developed or aggravated hydronephrosis deteriorates differential renal function after extravesical ureteral reimplantation. We performed extravesical ureteral reimplantation in 93 patients with unilateral vesicoureteral reflux between January 2006 and December 2009. Excluding 3 patients with other combined disease, a retrospective cohort analysis of 90 consecutive patients was conducted. We performed ultrasonography before and 1 month after extravesical ureteral reimplantation, and dimercapto-succinic acid scan before and 6 months after extravesical ureteral reimplantation. Of the patients 83 underwent final dimercapto-succinic acid scan at 6 months postoperatively. We analyzed the preoperative studies and perioperative parameters to evaluate the factors affecting newly developed or aggravated hydronephrosis at 1 month, and decrease in differential renal function at 6 months after extravesical ureteral reimplantation. Newly developed or aggravated hydronephrosis was observed in 25 patients (28.4%) 1 month after extravesical ureteral reimplantation. Younger age at surgery was a risk factor (p = 0.003). Of the patients 23 showed improvement on ultrasound 6 months postoperatively. In 12 patients (15.7%) a decrease in differential renal function of more than 5% was observed 6 months postoperatively. Preoperative parenchymal reduction on dimercapto-succinic acid scan was the only significant factor (p = 0.008). There was no correlation between newly developed or aggravated hydronephrosis and final decrease in differential renal function (p >0.999). Although newly developed or aggravated hydronephrosis after extravesical ureteral reimplantation is common, especially in younger patients, it is transient and does not affect differential renal function. A postoperative decrease in differential renal function without further urinary tract infection could develop when there is a parenchymal reduction on preoperative dimercapto-succinic acid scan.