The bladder is a hollow organ located in the lower part of the abdomen that functions to collect urine before removing it from the body through the urethra. Interstitial cystitis, also called painful bladder syndrome, is a chronic condition characterized by an inflammation of the bladder wall tissue. Interstitial cystitis is more common in young and middle-aged women. The exact cause of interstitial cystitis is unknown. A defect in the protective lining of the bladder may allow toxic substances in the urine to cause irritation of the bladder wall, resulting in interstitial cystitis.