ObjectiveTo determine the prevalence of hydronephrosis in patients undergoing surgery for pelvic organ prolapse and to determine whether hydronephrosis is associated with the type and severity of prolapse.MethodsThe charts of 375 consecutive patients undergoing surgery for pelvic organ prolapse at the Cleveland Clinic Foundation between January 1, 1990, and December 31, 1993 were reviewed. Preoperative renal ultrasounds and intravenous pyelograms (IVP) were evaluated for hydronephrosis based on the final diagnosis established by the radiologists. The severity of prolapse was determined from the preoperative office examination or from the examination under anesthesia at the time of surgery.ResultsOf 375 patients, 323 had either a preoperative renal ultrasound or IVP. The mean age was 66.0 ± 10.2 years (range 35–93) and median parity was 3.0 (range 0–10). Of the 323 patients, 25 (7.7%, 95% confidence interval 5, 11) had hydronephrosis. Thirteen patients (4.0%) had mild hydronephrosis, nine (2.8%) had moderate hydronephrosis, and three (0.9%) had severe hydronephrosis. The prevalence of hydronephrosis increased with increasing severity of prolapse. Two patients with hydronephrosis had evidence of renal insufficiency (creatinine ≥ 1.6), and both had severe bilateral hydronephrosis and complete procidentia. The prevalence of hydronephrosis was lower in patients with vaginal vault prolapse versus uterine prolapse (3.9% compared with 12.6%,P< .01).ConclusionThe prevalence of hydronephrosis in patients undergoing surgery primarily for pelvic organ prolapse is low, increases with worsening pelvic organ prolapse, and is lower in patients with vaginal vault prolapse than in those with uterine prolapse.