Taken from a site;- (easier than bothering to think what to write)
The term "cystitis" literally means irritation of the urinary bladder. Although this term is rather general, there is a common form of cystitis that occurs in male and female cats. This disease is also known as Feline Urologic Syndrome (FUS) or Feline Lower Urinary Tract Disease (FLUTD). It affects the bladder (not the kidneys), resulting in the production of tiny crystals and bloody urine. The cat often urinates much more frequently than normal, usually with the passage of only a few drops of urine. This can be confused with constipation. Many cats will urinate in places other than the litter box due to the irritation of the bladder wall, Hard cool surfaces such as tile floors, counter tops, sinks, and bathtubs are often used. They should not be punished for doing so.
We are not completely sure of the cause of this problem. Bacterial infections are the most common cause of cystitis in dogs and humans, but most cats with cystitis do not have bacteria in their urine. Dry foods may not initiate, but will aggravate the problem after it begins. This is because of the higher mineral content (ash) and lower water content of dry foods. A herpes virus has also been incriminated.
