Interstitial cystitis (IC) is a poorly understood disease with unknown origins that produces chronic inflammatory condition of the bladder that causes frequent, urgent, and painful urination and pelvic discomfort. The natural lining of the bladder (epithelium) is protected from toxins in the urine by a layer of protein called glycoaminoglycan (GAG). In IC this protective layer has broken down, allowing toxins to irritate the bladder wall. The bladder then becomes inflamed and tender and does not store urine well.

Unlike inflammation of the bladder caused by bacterial infection (cystitis), which is associated with urinary tract infections (UTI) and usually treated with antibiotics, no infectious agent has been found in IC. Though not curable, IC is treatable and most patients find some relief with treatment and lifestyle changes.

IC may occur following gynecological surgery. Some evidence suggests an increased risk for IC in Jews; and studies of mothers, daughters, and twins who suffer from it suggest a hereditary risk factor.