Histological evidence supports low anesthetic bladder capacity as a marker of a bladder-centric disease subtype in interstitial cystitis/bladder pain syndrome

Introduction and hypothesis: Low anesthetic bladder capacity has been shown to be a biomarker for bladder-centric interstitial cystitis/bladder pain syndrome (IC/BPS). The goal of this study was to determine if histopathological evidence from bladder biopsies supports anesthetic bladder capacity (BC) as a marker to distinguish a bladder-centric IC/BPS subtype.

Methods: From a review of our large IC/BPS cohort of patients undergoing hydrodistention, we identified a total of 41 patients with low BC (≤ 400 ml); an additional 41 consecutive patients with BC > 400 ml were selected as the comparator group. The original bladder mucosal biopsy pathology slides were re-reviewed by a single pathologist (blinded to patient information) using a standardized grading scale developed for this study.

Results: Histologically, the low BC subjects exhibited higher levels of acute inflammation (p = 0.0299), chronic inflammation (p = 0.0139), and erosion on microscopy (p = 0.0155); however, there was no significant difference in mast cell count between groups (p = 0.4431). There was no significant gender difference between the groups; female patients were the majority in both groups (low BC: 94.12%, non-low BC: 100%; p = 0.1246). Individuals in the low BC group were older (p < 0.0001), had a higher incidence of Hunner's lesions on cystoscopy (p < 0.0001), and had significantly higher scores, i.e., more bother symptoms, on two IC/BPS questionnaires (ICPI, p = 0.0154; ICSI, p = 0.0005).

Conclusions: IC/BPS patients with low anesthetic bladder capacity have histological evidence of significantly more acute and chronic inflammation compared with patients with a non-low bladder capacity. These data provide additional evidence to support low bladder capacity as a marker of a distinct bladder-centric IC/BPS phenotype.