Use of renal ultrasound to detect hydronephrosis after ureteroscopy.

INTRODUCTION: Ureteral obstruction is a potentially serious complication after ureteroscopy. Postoperative imaging with intravenous urogram and CT has been described as a means to detect asymptomatic or "silent" obstruction. We sought to evaluate the use of renal ultrasound to diagnose hydronephrosis after ureteroscopy in a large, contemporary series.
MATERIALS AND METHODS: Of the 438 ureteroscopies performed by one staff surgeon at our institution from August 2003 to June 2008, 289 underwent a strict follow-up protocol that included renal ultrasound at approximately 1 month from the date of operation in patients without a stent or 1 month from the date of stent removal in patients with a stent.
RESULTS: Of the 289 patients with proper follow-up, 27 (9.3%) had sonographic evidence of hydronephrosis. Fourteen patients were asymptomatic, and 13 patients experienced ipsilateral flank pain. A total of 4.8% of the patients (14/289) had silent hydronephrosis. The negative predictive value and positive predictive value of ipsilateral flank pain for hydronephrosis were 94% and 35%, respectively. There was no difference between the symptomatic and asymptomatic groups with respect to need for further surgery (38% vs. 21%, p = 0.42). The number of asymptomatic patients after ureteroscopy needing renal ultrasound to diagnose one case of hydronephrosis was 18.
CONCLUSIONS: This study demonstrates that hydronephrosis is present in a small percentage of patients after ureteroscopy. Hydronephrosis can be present in both symptomatic and asymptomatic patients and may warrant further surgery. Renal ultrasonography at 1 month after ureteroscopy permits appropriate detection of hydronephrosis and should be considered as an imaging option.