To investigate the relationship between bladder capacity measured during hydrodistension and symptom scores in patients diagnosed with bladder pain syndrome (BPS).

Between January 2024 and December 2024, a total of 40 adult patients who underwent diagnostic cystoscopy and hydrodistension under general anaesthesia due to suspected BPS were included in the study. All patients underwent bladder hydrodistension for 5 minutes at a pressure of 80 cm H₂O. After hydrodistension, bladder capacity was measured. Demographic characteristics, perioperative findings, and symptom scores were retrospectively reviewed. Correlation analyses were performed between intraoperatively measured bladder capacity and demographic variables, uroflowmetry parameters, and symptom scores, including the Interstitial Cystitis Symptom Index (ICSI), Interstitial Cystitis Problem Index (ICPI), Overactive Bladder Validated 8-question score (OAB-V8), and Visual Analog Scale (VAS). Endoscopic findings were also evaluated, and subgroup analyses were conducted.

The mean age of the patients was 48.51 years; 7 (17.5%) were male and 33 (82.5%) were female. The median symptom duration was 62 months (range: 6–240 months). Thirteen patients (32.5%) had a history of hydrodistension. The mean bladder capacity measured during hydrodistension was 618.87 ± 215.4 ml. Correlation analysis revealed a significant negative relationship between bladder capacity and ICSI score (p = 0.027). Bladder capacity was positively correlated with maximum urinary flow rate (Qmax) and voided volume. Furthermore, all four symptom scores were positively correlated with each other. Among the patients with glomerulations, 75% had grade 1 and 25% had grade 2 glomerulations. In subgroup analysis based on the presence of glomerulations, no significant differences were found in symptom scores; however, Qmax was significantly lower in patients with glomerulations (p = 0.019).

These findings suggest that reduced bladder capacity may be associated with greater symptom severity in patients with BPS, as reflected by higher ICSI scores. This inverse relationship highlights the potential role of bladder capacity as a marker of disease burden.

A negative correlation has been identified between bladder capacity and ICSI score in patients with BPS. Prospective studies are needed to further clarify these relationships and subgroup differences, including the evaluation of treatment response and its association with bladder capacity.