Real-World Results of Urethral Bulking With Polyacrylamide Hydrogel Versus Legacy Injectables: A Retrospective Study

Urethral bulking agents are established minimally invasive treatments for stress urinary incontinence (SUI), though efficacy varies among available materials. Comparative evidence on contemporary bulking agents, particularly polyacrylamide hydrogel (PAHG), remain limited. This study aimed to compare retreatment rates following primary periurethral bulking with PAHG versus other FDA-approved agents.

We performed a multicenter retrospective cohort study of women undergoing primary periurethral bulking for SUI or stress-predominant mixed urinary incontinence between 2011 and 2024. Only current FDA-approved bulking agents were included. The primary outcome was retreatment, defined as any subsequent anti-incontinence procedure, including repeat bulking injections. Retreatment rates were estimated using Kaplan-Meier methods, with comparisons between PAHG and other agents, as well as between index and non-index patients treated with PAHG. Cox proportional hazards models assessed predictors of retreatment.

Among 623 women undergoing periurethral bulking, 268 (43.0%) received PAHG, 332 (53.3%) calcium hydroxyapatite, 12 (1.9%) polydimethylsiloxane, and 11 (1.8%) carbon-coated zirconium oxide. The median follow-up was 2.2 years (IQR 0.9-6.6). Overall, 223 patients (36.6%) underwent retreatment at 2 years (80.7% with repeat bulking, 11.2% with urethral sling placement, and 8.1% underwent both repeat bulking and urethral sling placement). Bulking injection with PAHG was associated with lower retreatment rates compared with other agents (1-year: 16.5% vs 34.8%; 2-year: 24.4% vs 44.3%; p < 0.001). After adjusting for comorbidities and procedural factors, PAHG use remained independently associated with a reduced risk of retreatment (HR: 0.53, 95% CI: 0.38-0.75; p < 0.001) as did concomitant prolapse surgery (HR: 0.40, 95% CI: 0.22-0.72; p < 0.001). Retreatment rates following PAHG injection did not differ between index and non-index patients (p = 0.73).

In this large multicenter cohort, PAHG was associated with significantly lower two-year retreatment rates compared with other FDA-approved bulking agents, with consistent effectiveness across index and non-index patients. PAHG may represent a more durable bulking option than legacy agents for the treatment of SUI in real-world practice, though long-term data remains limited.