Feline urinary obstruction (UO) is an acute obstruction of the urinary tract, and although this disease can affect any cat, it is most common in males. It can be caused by stones, but usually it's cause is a plug of inflammatory debris and crystals as part of the common syndrome called feline idiopathic cystitis (FIC), which is an inflammation of unknown cause affecting the lower urinary tract. Factors that may play a role in the development of FIC include viruses, diet (dry food diets with high mineral content), stress, strict confinement, and genetic factors (long-haired cats seem to be more affected).
Other medical problems can lead to symptoms similar to those encountered in FIC. These conditions should be excluded before establishing a diagnosis of FIC. Some of them include: Bacterial urinary infection (bacterial cystitis). A bacterial cystitis is an uncommon cause of lower urinary tract symptoms in young to middle-ages cats.
Bladder stones (calculi or uroliths)Urolithiasis
Congenital anatomic abnormality. These are defects present at birth such as outpouching of the bladder.
Constipation. It is easy to confuse difficult urination and difficult defecation. Observing your cat's posture may help because cats assume a more upright posture when defecating.
Tumors of the bladder. These are rare in cats.
Nervous system abnormalities. These sometimes interfere with the normal control mechanisms of urination.
Inappropriate urination as a result of behavioral disorder. Cats are territorial by nature, and when they sense their "space" has been invaded, they often mark their territory by urinating outside the litter box. It might be difficult to distinguish this behavior from symptoms of FIC.