Interstitial cystitis (also referred to as painful bladder syndrome) is a chronic bladder condition of unknown etiology. It is formally defined by the American Urological Association as an unpleasant sensation (pain, pressure, or discomfort) perceived to be related to the urinary bladder and associated with lower urinary tract symptoms of more than 6 weeks' duration, in the absence of infection or other identifiable causes.

Historically, it was believed that the potential pathophysiology was related to damage to the urothelium provoking an inflammatory response. Potential triggers were thought to include infection, pelvic surgery, pelvic floor muscle dysfunction, bladder overdistention, pelvic floor injury, and spinal cord issues. Currently, the etiology is less clear, and interstitial cystitis is grouped with other chronic pain conditions such as fibromyalgia and irritable bowel syndrome (IBS). This condition can occur at any age, although it is seen most often at midlife and more commonly in females.

Patients will present with symptoms of dysuria, increased urinary frequency and urgency, pelvic pain and pressure, as well as possible dyspareunia. Most commonly, patients will report pain with the bladder being full, which is relieved upon emptying.
 
Symptom onset is usually gradual over a number of months. Sometimes a triggering event can be identified, but more often the onset is insidious.