Interstitial cystitis (IC) is a chronic pelvic pain disorder. It is characterized by irritation or inflammation of the bladder wall. The main symptom of this condition is recurring pain or discomfort in the bladder and pelvic region.

The symptoms and severity of IC vary greatly among individuals. Most researchers believe that IC is caused by several diseases rather than a single disease. The condition is typically chronic, rather than acute or progressive, which means that symptoms do not typically become worse over time, but remain constant. In women, symptoms of IC can become more severe before or during menstruation.

Although the cause of IC remains unknown, some researchers theorize that the condition is an autoimmune response to the triggering factors of a urinary tract infection. Others speculate that IC may occur when the bladder wall becomes damaged and allows irritants in the urine to penetrate its deeper layers. Heredity may also be a factor in developing the condition.

Some symptoms of IC resemble the symptoms typically caused by a bacterial infection of the bladder. However, medical tests have found no bacteria present in the urine of IC patients. In addition, IC patients are unresponsive to antibiotics, which are usually effective in treating bacterial infections.

Previously, IC cases were mainly classified as either ulcerative or nonulcerative, depending on whether ulcers had formed on the patient’s bladder wall. However, there is much debate over whether this classification is useful. 

Most IC cases are nonulcerative and factors, such as the capacity of the bladder or the presence of mast cells have greater influence on treatment decisions. These elements can be obtained when the bladder is measured and examined while under anesthesia. Mast cells in the tissues of the bladder may indicate an allergic or autoimmune reaction. In some cases, the success or failure of treatments (e.g., whether IC responds to dietary changes) may help characterize the type of interstitial cystitis.

There is no diagnostic test that exclusively identifies IC at this time. Tests that may be performed include a variety of diagnostic tests, including urine tests and cystoscopy, a procedure that uses a lighted scope to view the inside of the urethra and bladder.

According to the National Institute of Diabetes and Digestive and Kidney Diseases, around 1.3 million Americans are estimated to have this condition. Women account for 90 percent of cases. Researchers are working to identify the cause of this condition and develop less-invasive diagnostic techniques.