(Poster 72) Impact of Methenamine Hippurate on Postoperative Urinary Retention & Infections

Objectives: Postoperative urinary retention (POUR) rates after pelvic organ prolapse (POP) and stress urinary incontinence (SUI) surgery range from 2.5-43% with bladder decompression the standard treatment. At our institution, an indwelling catheter is placed for POUR with planned outpatient voiding trial around postoperative day 3. Indwelling catheterization and surgery near and/or involving the urethra are known risk facts for UTIs.

Methenamine hippurate (MH) is a well-established bacteriostatic agent that can be used to prevent UTI without the risk of contributing to bacterial resistance. Starting in April 2024, patients at our institution who developed POUR were discharged on MH (1 gram orally twice daily) for the length of indwelling catheter use. This study investigated the impact of MH on POUR duration and incidence of UTI postoperatively.

Methods: This retrospective study included patients undergoing POP or SUI surgery between April 1 – November 30, 2023, and April 1 – November 30, 2024. Exclusion criteria included surgery outside collection dates; known MH allergy/sensitivity; medications or medical conditions affected by MH; preoperative urinary retention (PVR > 150); intraoperative cystotomy or other condition requiring long-term catheterization. POUR duration and incidence of postoperative UTI (at 6 and 12 weeks) was compared using Fisher Exact and Chi-square with a level of significance at 0.05 and odds ratio with 95% confidence interval. Linear regression examined the relationship between catheter days and MH, with covariates of age and BMI. Logistic regressions examined the relationship between UTI and MH, with covariates of catheter days and age.

Results: Of the 217 eligible patients, 35 patients (22 in 2023, 13 in 2024) had POUR and were discharged with indwelling catheters. Five patients in 2024 did not receive MH and were included in the control group. This group, who did not receive MH, were compared to the eight who received MH. There was no difference in age, menopausal status, BMI, or EBL between the two groups (Table 1). Duration of catheter use in the MH group was 4.00 ± 3.29 days (95% CI 1.25-6.75) compared to 4.93 ± 3.82 days (95% CI 3.4-6.44). Age and duration of catheter placement were found to predict postoperative UTI while use of MH was not. (Table 2)

Conclusions: MH use did not have a statistically significant impact on duration of catheter placement. Yet, the MH group had resolution of POUR sooner, as measured by catheter use of 4 days versus 4.9 days; this may be clinically significant. MH use does not appear to impact incidence of UTI in this small sample size. The data supports increased rates of postoperative UTI are associated with increased age and duration of catheter use. The greatest limitation was the small sample size of those discharged with MH. MH use continues with planned future study expansion.