The most common reason for performing surgery on the bladder is to remove uroliths, or bladder stones.  These are very common in certain breeds of dogs (Miniature Schnauzers, Bichons, Shih Tzu, Dalmation, etc) and can lead to blockages of the urethra preventing urination.  This is an emergency that needs to be addressed immediately.  Dogs and cats that are "blocked" are straining to urinate but little to no urine is produced. We often diagnose bladder stones during the work-up for a bladder infection.  Animals that are prone to bladder stones are often put on a special diet to help prevent the formation of these stones.