Comparing Acute Urinary Retention Rates: Slings versus Polyacrylamide Hydrogel

Objectives: Stress urinary incontinence is a common and bothersome condition affecting up to 30% of women. Midurethral slings are considered the gold standard for surgical treatment of SUI, with an efficacy up to 80%. Another therapeutic option is the use of bulking agents, which create an artificial mass in the urethral submucosa contributing to urethral coaptation. According to the literature, urinary retention rates after polyacrylamide hydrogel injections were found to be 5% and 20% after retropubic sling procedures. We hypothesize that the acute urinary retention rates after bulking are comparable to those of midurethral slings. The objective of this study was to evaluate the acute post-operative retention rates after retropubic sling placement compared to transurethral bulking with polyacrylamide hydrogel.

Methods: This was a retrospective cohort study done at a tertiary care center from October 2021 to November 2023. Study participants were identified by Current Procedure Terminology codes corresponding to retropubic midurethral slings and polyacrylamide hydrogel injections. Pregnant patients, those under 18 years of age and undergoing concomitant procedures were excluded. Based on the literature reported urinary retention rates, we determined that 76 patients were needed per group to achieve an 80% power with a p < 0.05. The primary outcome was the rate of urinary retention determined by post-operative voiding trials. OAB symptoms, smoking status, menopausal status and operative times were assessed as predictors of acute urinary retention.

Results: We reviewed 310 charts and found 152 to meet inclusion criteria, allocating 76 patients per study arm. Patients who received polyacrylamide hydrogel injections were older, more likely to be post-menopausal and diabetic than in the midurethral sling group. More of the patients who underwent midurethral slings were sexually active and had baseline OAB symptoms. Patients who underwent bulking injections had a higher rate of voiding trial failure post-operatively, but this was not statistically significant, 17.1% vs 14.5% (p=0.66). Post-operative UTI rates were higher in the sling group, 10.5% vs 2.6% (p=0.05). Premenopausal patients were more likely to pass the voiding trial, but this was not statistically significant, 90.6% vs 79.5% (p=0.06). BMI, vaginal estrogen use, diabetes or pre-operative OAB symptoms were not associated with the likelihood of passing a voiding trial. OAB symptoms resolved in 51.3% of patients undergoing slings and in 25.0% of patients undergoing bulking (p < 0.001). Age was a significant predictor of the likelihood of failing the voiding trial in the bulking group (p=0.003).

Conclusions: Our results showed that the acute urinary retention rates after bulking are higher than previously reported in the literature and are comparable to those of midurethral slings. Increasing age is a risk factor which could predict voiding trial failure in bulking patients. OAB symptoms were more likely to resolve in patients undergoing midurethral slings.