Cystitis is an inflammation of the bladder that is common in pets, especially cats. It is not just an “inconvenience,” but a serious condition that requires the owner’s attention and professional help. 🐾 What is cystitis and why does it occur? Cystitis is an inflammation of the mucous membrane of the bladder , which can be caused by: bacterial infection; hypothermia; stress; urolithiasis; unbalanced diet; sedentary lifestyle. This disease is more common in cats than in dogs