Urine, produced by the kidneys, is stored in the urinary bladder before exiting the body through the urethra. The urethra acts as a channel for urine excretion; its length offers protection against infection from the outside. Cats with urinary bladder inflammation (cystitis) strain to produce small amounts of urine (may be mistaken for constipation), urinate outside the litter box, and may have blood in their urine. Common causes of cystitis include feline idiopathic interstitial cystitis, stones, polyps, and tumors. Urinary tract infections affect cats less commonly (<5%) due to their highly concentrated urine. Suspicion of feline cystitis is based on history and physical examination; definitive diagnosis requires a urinalysis, urine culture, and abdominal x-rays. Complicated cases of cystitis may require more advanced imaging with ultrasound and/or contrast studies. Treatment for cats with uncomplicated (non-obstructive) cystitis includes a combination of fluid therapy to help flush the bladder, dietary changes, pain relief, and medications to alleviate bladder spasms and restore normal urine flow. Antibiotics are indicated only when an infection is found. An inability to urinate (straining with no urine production) requires emergency treatment to relieve the painful, life threatening urinary tract obstruction.