Interstitial cystitis (IC): Disease that involves inflammation or irritation of the bladder wall. This inflammation can lead to scarring and stiffening of the bladder, and even ulcerations and bleeding. Diagnosis is based on symptoms, findings on cystoscopy and biopsy, and eliminating other treatable causes such as infection. Because doctors do not know what causes interstitial cystitis, treatments are aimed at relieving symptoms. Most people are helped for variable periods of time by one or a combination of treatments.