Maximal bladder capacity (MBC), grade of glomerulations (Glom) and presence of Hunner’s ulcer are the three major findings/parameters of cystoscopic hydrodistention used for diagnosis of interstitial cystitis/bladder pain syndrome (IC/BPS). Based on the finding on Hunner’s ulcer, IC/BPS has been traditionally classified into the ulcer type and non-ulcer type which have been considered as two distinct diseases. However, the role of other two cystoscopic parameters (MBC and Glom) on the clinical characters of IC/BPS has not been elucidated. We investigated the correlations between clinical variables and the phenotype based on Glom and MBC subgroups in IC/BPS patients.

IC/BPS patients who have undergone cystoscopic hydrodistention were retrieved from a database containing 496 subjects. According the severity of Glom (grade 0, 1, 2, 3, 4) and MBC (≥760 or <760 mL) measured during hydrodistention, the patients were categorized into five phenotypes (PTs): PT1) Glom=0/1, MBC≥760. PT2) Glom=0/1, MBC<760. PT3) Glom=2/3, MBC≥760. PT4) Glom=2/3, MBC<760. PT5) Glom=4 (ulcer type). Clinical variables including age, gender, disease duration, prevalence of various functional somatic syndromes, number of medical comorbidities, IC symptom scores, urodynamic study (UDS) parameters such as first sensation of filling (FSF), first desire to void (FD), strong desire to void (SD), maximum flow rate (Qmax), detrusor pressure at Qmax (Pdet), voided volume, postvoid residual volume (PVR), cystometry bladder capacity (CBC) and compliance, and video UDS diagnoses, result of potassium sensitivity test (PST) and long-term treatment outcome were analyzed and compared among the five IC/BPS phenotypes.

A total of 488 IC/BPS patients (male:female=65:423; mean age, 58.8±13.8; mean duration: 13.6±9.8 years; mean follow-up: 5.8± 5.1 years) were included in this study. There were significant differences in mean age, distributions of psychosomatic disorder (PSD) and arrhythmia and number of comorbidities among the five IC/BPS PTs (Table 1). PT5 had the oldest age and highest prevalence in PSD while PT1 and PT3 had the highest prevalence in arrythmia. The mean number of comorbidities decreased from PT1 through PT4. In addition, the mean IC symptom scores increased from PT1 to PT5. The UDS storage parameters (FSF, FD, SD, CBC, volume) and compliance decreased from PT1 to PT5. Also, the prevalence of hypersensitive bladder (HSB) increased from PT1 to PT5. There was no significant difference in distributions of gender, duration, video UDS diagnoses, result of PST and long-term treatment outcome among the five PTs.

With combination of the two cystoscopic parameters (grade of Glom and MBC), the five PTs (from PT1 to PT5) represent increased severity of bladder pathology in patients with IC/BPS. Significant differences in mean age, distributions of PSD and arrhythmia and number of comorbidities reflect the distinct nature of the five IC/BPS PTs. The fact that the mean number of comorbidities decreased from PT1 through PT4 may imply the systemic involvement decreased as the severity of bladder pathology increased in non-ulcer type IC/BPS. Our results further demonstrated the positive correlation of symptom scores, and negative correlation of UDS storage parameters with the five PTs, indicating the clinical value of the novel IC/BPS phenotype system based on Glom and MBC subgroups.

This study demonstrated the novel IC/BPS phenotype system based on the severity of bladder pathology (Glom and MBC subgroups) was correlated well with the symptom scores, UDS storage parameters and compliance, and prevalence of HSB, providing a valuable tool for clinical description and patient counseling.