478 40% of patients having a post-voiding residual of more than 200 mL after removal of the catheter on the first postoperative day versus 9% of patients having retention after removal of the catheter on the fifth postoperative day [2]. We concluded that removal of the indwelling catheter on the first day postoperatively is too soon. Based on these conclusions, we hypothesized that 2 days of indwelling catheterization postoperatively after an anterior colporrha- phy is more appropriate than 5 days, which is most commonly applied in The Netherlands. Bladder catheterization, however, increases the risk of urinary tract infections [5]. After removal of the catheter on the first day postoperatively, only 4% of patients had infections, compared to 20% when the catheter had been removed on the third day and 40% after removal of the catheter on the fifth day [2, 4]. In a retrospective study, high-grade cystocele, higher intra-operative blood loss, Kelly plication, and levator plication were identified by multivariable analysis as independent risk factors for short-term urinary retention after vaginal prolapse surgery [6]. The aim of the present study was to determine in a randomized controlled trial the incidence of bladder retention and urinary tract infections after postoperative indwelling catheterization for 2 days versus indwelling catheterization for 5 days. Methods Between January 2006 and September 2008, a random- ized controlled trial was performed in three different hospitals in patients undergoing an anterior colporrhaphy comparing postoperative temporary indwelling catheteri- zation for 2 days versus indwelling catheterization for 5 days. The primary outcome measure was the number of temporary catheter replacements after the first removal of the catheter postoperatively. A catheter was temporarily replaced in case the residual volume after micturition was more than 200 mL. Despite the definition of the International Continence Society for bladder retention, which is one third of the bladder volume, the cut-off value of 200 mL was chosen to make the results of the study comparable to those of another study [2]. Second- ary outcome measures were the rate of urinary tract infections and the length of the hospital stay. Furthermore, the factors that appeared to be associated with post- voiding residuals more than 200 mL after removal of the catheter in univariable regression were assessed by multivariate logistic regression to find out if they were independent risk factors for temporary catheter replace- ments. The assessed factors in univariable analysis were age, BMI, history of obstructive micturition or recurrent Int Urogynecol J (2011) 22:477–483 urinary tract infections, advanced stage of prolapse preoperatively, used operation techniques, concomitant surgery, mean amount of blood loss, urinary tract infections, and the protocol for catheterization used. All patients with a cystocele undergoing an anterior colporrhaphy were eligible. As the POP-Q classification was not generally introduced in daily practice at the study start, prolapse was staged at the outpatient clinic according to the Baden–Walker classification. Stage I was a cystocele, rectocele, or descensus uteri into the first half of the vagina, in stage II the prolapse protruded into the distal half of the vagina, in stage III the prolapsed tissue bulged out of the vagina, and stage IV was a total protrusion of the bladder, rectum, or uterus. Doctors were encouraged to perform the anterior repair as they were used to. Combinations with other vaginal operations like hysterectomy, sacrospinal fixation, or posterior colporrhaphy were allowed. Excluded were women who were performing self-catheterization because of voiding dysfunctions preoperatively, women under 18 years of age, and those who were not able to understand informed consent because of low IQ or a language barrier. After informed consent, patients were included at the outpatient clinic at the time the operation was planned. The protocol was approved by the medical ethical commit- tees of the three participating hospitals. Patients were randomized to postoperative temporary indwelling catheterization for either 2 or 5 days. A randomization list was made by an independent statistician. Randomization was performed in blocks and was stratified for the different hospitals. According to the randomization list, opaque, numbered, and sealed envelopes were prepared by an independent person. At the start of the operation, urine was collected for sedimentation. After the operation was finished, the indwelling catheter was inserted; the envelope with study number was opened, and at that moment, the patient was randomized to temporary indwell- ing catheterization for either 2 or 5 days. The catheter was removed in the morning of the second or fifth day postoperatively. The residual volume was measured by bladder ultrasound scan 6–8 h later. A residual volume after micturition of more than 200 mL was considered abnormal, and a new indwelling catheter was inserted. A required minimum void was not defined. The next morning, the catheter was removed, and again the post-voiding residual volume was assessed 6–8 h later. If the volume was still more than 200 mL, a new catheter was inserted, this time for 3 days. In case the residual volume was still more than 200 mL after these three extra days, the patient started intermittent self- catheterization until the residual volume after spontaneous micturition was less than 200 mL. All patients received prophylactic antibiotics at the beginning of the operation. Postoperative prophylactic