A Review of the Etiopathology of Phenotypes in Interstitial Cystitis/Bladder Pain Syndrome

Aims: The aim of this manuscript was to provide a narrative review of the etiopathology of three different interstitial cystitis/bladder pain syndrome (IC/BPS) phenotypes: Hunner lesion, widespread pain, and low bladder capacity. Methods: IC/BPS literature was reviewed by the authors specific to the three phenotypes, focusing on etiopathology. Evidence was condensed and summarized on the different causes of each phenotype, emphasizing papers and abstracts dealing with basic science research, symptoms, and treatment options for patients afflicted with the three different IC/BPS phenotypes. Results: Hunner lesion patients are marked by a distinct, visible inflammatory lesion in the bladder, inflammatory serum and urinary biomarkers, and respond well to bladder-centric treatments targeted specifically at the Hunner lesions. Widespread pain patients have diffuse pain attributed to central nervous system changes manifesting in the bladder, often with co-occurring non-bladder chronic pain conditions such as fibromyalgia and seem to respond better to systemic therapies. Low bladder capacity patients have a marked decrease in anesthetic bladder capacity during therapeutic hydrodistension of the bladder. They also tend to have higher pain scores, symptoms specifically concentrated at the bladder, and respond to localized treatments, constituting another bladder centric phenotype. Conclusions: IC/BPS should not be thought to represent one unique type or pathophysiology, but rather a diverse group of patients, each with their own etiopathology and phenotypic manifestations. Clinical Trial Registration: This was a narrative review and did not involve any direct intervention on patients nor direct patient contact and was not a clinical trial.