Pathophysiology of Interstitial Cystitis/Bladder Pain Syndrome: Update on Urothelial and Neural Mechanisms

Abstract

Introduction: Interstitial cystitis/bladder pain syndrome (IC/BPS) is a debilitating chronic condition of unclear etiology. This review critically evaluates emerging evidence on urothelial barrier dysfunction, mast cell activation, and peripheral sensitization.

Methods: A narrative synthesis of basic science and translational studies (2015–2024) from PubMed and Google Scholar. Inclusion: original research on human bladder tissue or validated animal models, reporting on urothelial permeability, nerve density, or inflammatory mediators. Exclusion: studies on Hunner lesions only.

Results: Forty-two studies were included. Impaired tight junction proteins (ZO-1, occludin) were found in 81% of IC/BPS biopsies versus 12% of controls. Urinary antiproliferative factor (APF) was elevated (sensitivity 89%). Mast cell density in detrusor was increased 3-fold, with tryptase levels correlating with pain scores (r=0.67). Suburothelial nerve fiber density (PGP9.5-positive) increased by 210% in non-Hunner IC/BPS.

Discussion: Evidence supports a model of primary urothelial leak leading to potassium diffusion, mast cell activation, and neurogenic inflammation. Heterogeneity between Hunner and non-Hunner subtypes likely reflects distinct pathobiology. Most animal models do not replicate human chronicity.

Conclusions: Interstitial cystitis/bladder pain syndrome involves convergent urothelial, inflammatory, and neural abnormalities. Subtype-specific biomarkers are needed to guide targeted therapy (e.g., antihistamines vs. bladder instillations).