Aetiology

Various aetiologies have been postulated, yet none definitively explain the multitude of presentations, clinical courses, or response to therapies. The condition is most probably a multifactorial disease process, with one or more of the following causative factors present:[14][15]

  • Autoimmune disorder

  • Creation of toxic substances in the urine, followed by glycosaminoglycan-layer deficiency, which lets these toxic substances permeate the bladder's submucosal tissues

  • Hypersensitivity to bladder inflammation

  • Pelvic-floor muscle dysfunction

  • Infection that resists immediate identification or cure.

  • Up-regulation of pelvic c-fibre afferent signals, triggering central sensitisation and sacral reflex signalling. This leads to pelvic floor dysfunction, hypersensitivity to normal stimuli, and resistance to local or regional therapies.

Pathophysiology

The pathophysiology is poorly understood. Prevailing theories include up-regulation of nerve growth factors leading to chronic stimulation of afferent pain sensations. Through poorly understood feedback and sacral reflex mechanisms, this leads to pelvic floor dysfunction, myofascial trigger points, and pain. The ulcerative form of the disease has no unifying theory on the inflammatory and fibrotic changes seen. Treatment has been associated with normalisation of some urinary cytokines, suggesting a paracrine response to some underlying endothelial or neurological dysfunction.

Classification

International Consultation on Incontinence classification[6]

Bladder pain syndrome (BPS)

  • An unpleasant sensation (pain, pressure, discomfort) perceived to be related to the urinary bladder, associated with lower urinary tract symptom(s) of more than 6 weeks' duration, in the absence of infection or other identifiable causes.

Interstitial cystitis (IC)

  • Patients manifest the same symptoms as with BPS but with the co-requisite cystoscopic findings due to inflammatory changes in the bladder.

Interstitial cystitis/bladder pain syndrome clinical classification (ESSIC criteria)[4]

IC may be divided into subgroups based on intra-operative findings at cystoscopy with bladder distension.[4]

Non-ulcerative

  • This type is epitomised by the same clinical symptoms as the classic form, but the cystoscopic findings present in the classic form are absent. (ESSIC type 1.) However, after over-distension, many of these patients demonstrate glomerulations (discrete, tiny, raspberry-like lesions appearing as minuscule mucosal tears and haemorrhages). This is also sometimes seen in patients without symptoms, calling into question this clinical finding. (ESSIC type 2.)

  • Bladder biopsy findings are normal or non-specific and usually not required. (ESSIC type A/B.)

Ulcerative (previously termed classic IC)

  • The characteristic features are 1 or more ulcerative patches surrounded by mucosal congestion on the dome/lateral walls of the bladder. (ESSIC type 3.)

  • Biopsy findings demonstrate that the ulcerative lesions can be transmural and are associated with marked inflammatory changes, granulation tissue, mast cell infiltration, and, in some cases, fibrosis. (ESSIC type C.)

  • This type accounts for <10% cases in the US and is rare.[7]

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