What is feline idiopathic cystitis?

According to the Cornell University College of Veterinary Medicine, feline idiopathic cystitis, also known as "interstitial cystitis," is inflammation of a cat's bladder with no known cause. It is the main cause of feline lower urinary tract disease, or FLUTD.

A cat with feline idiopathic cystitis has a bladder that is easily felt through the skin, pain in reaction to the bladder being touched, lack of urination, frequent attempts to urinate without producing a stream, and blood in the urine that is produced. The diagnosis is given to cats that show these symptoms but do not have any other obvious cause for them, like a bacterial infection or kidney stones. The illness is often in reaction to stress, such as a sudden change in routine.