ObjectiveHyaluronic acid (HA) is currently used in Taiwan as intravesical instillation for the treatment of interstitial cystitis/bladder pain syndrome (IC/BPS). This study investigated the therapeutic effects of HA on IC/BPS in the Taiwanese population.Materials and methodsMen and women aged ≥18 years with documented IC/BPS were initially treated with four weekly intravesical HA instillations (treatment time, 1 month) and then with five monthly instillations (total treatment time, 6 months). Clinical assessments included the evaluation of the Visual Analog Scale (VAS) score of bladder pain, O'Leary–Sant Symptom (OSS) score, IC Symptom Index (ICSI), IC Problem Index (ICPI), functional bladder capacity (FBC), uroflowmetry parameters, and global response assessment (GRA). Therapeutic effects were compared between responders (GRA increased ≥ 2 scales) and nonresponders (GRA increased < 2). Multivariate linear analysis was used to determine predictive factor for successful treatment.ResultsA total of 64 patients (3 men and 61 women) with mean age of 49.4 years (range, 20–79) completed the study. Compared with the baseline data, VAS, ICSI, ICPI, OSS score, daytime frequency, nocturia, and FBC all improved at 1 month or 6 months after starting HA treatment. Significantly more improvements in ICSI, ICPI, OSS score, VAS, and FBC were noted in the responders than in the nonresponders at 6 months of treatment. A low-grade glomerulation was the only predictor for successful treatment response to intravesical HA treatment.ConclusionIntravesical HA administrations improved IC symptoms, decreased bladder pain, and decreased frequency after four instillations, and decreased nocturia and increased bladder capacity after completion of all nine instillations. Low-grade glomerulation predicts successful outcome