Adjuvant bladder thermal irrigation for ultrasound-guided botulinum toxin a injection in refractory bladder pain syndrome: a retrospective cohort study.

[PURPOSE] This retrospective preliminary study aimed to evaluate whether adjuvant bladder thermal irrigation (TI) enhances the efficacy of ultrasound-guided botulinum toxin type A (BoNT-A) injection in patients with refractory bladder pain syndrome (BPS).

[METHODS] We analyzed patients with refractory BPS who received an initial ultrasound-guided injection of 100 U BoNT-A into the bladder trigone between February 2019 and January 2025. Patients were divided into two groups based on irrigation temperature: the Thermal Irrigation Group (TI Group, n = 38) received warm saline irrigation at 43 °C ± 2 °C, and the Room-Temperature Irrigation Group (CON Group, n = 38) received irrigation at 22-25 °C. Propensity score matching (PSM) was used to balance baseline characteristics. The primary endpoint was median duration of efficacy. Secondary endpoints included changes in Visual Analogue Scale (VAS) pain scores and O'Leary-Sant Symptom Score (OSS) at 1, 3, and 6 months, and the Global Response Assessment (GRA) at 6 months.

[RESULTS] After PSM, 32 matched pairs (n = 64) were included. The median duration of efficacy was significantly longer in the TI group than in the CON group (34.5 weeks vs. 24.0 weeks, log-rank test P = 0.012; HR = 0.52, 95% CI 0.31-0.88). At 3 months, the TI group demonstrated significantly greater pain reduction (adjusted mean VAS difference: -1.00, 95% CI -2.05 to 0.05, P = 0.008). At 6 months, the overall treatment success rate (GRA ≥ 2) was 71.9% in the TI group versus 50.0% in the CON group (OR = 2.57, 95% CI: 1.02-6.49, P = 0.043).

[CONCLUSION] Adjuvant bladder thermal irrigation was associated with a longer duration of efficacy and greater symptom improvement in refractory BPS patients receiving BoNT-A injection, with a favorable safety profile. These findings support the need for prospective randomized trials to confirm the role of thermal irrigation as an efficacy enhancer for intravesical BoNT-A therapy.