Feline lower urinary tract disease (FLUTD) is the term that replaces FUS, or feline urological syndrome. It describes many urinary tract related symptoms including straining to urinate, blood in the urine, inappropriate urination (out of the litter box), and inability to urinate (blockage). The term does not indicate the causes of the symptoms, which can be numerous. Typically, bladder infection is not the primary reason for FLUTD, but it can occur secondarily. In fact, frequently the underlying cause is speculative or unconfirmed.
More than half of cats with FLUTD under the age of 10 years will have an undetermined cause of their symptoms. Twenty percent may develop bladder stones or urethral blockage. Male cats have a tapering urethra, the tube that carries urine outside of the body. Because it narrows toward the opening, cells and mucous may dam up and form a blockage. This is called a urethral plug, and it is a life threatening emergency. The cat will usually howl or growl in pain while it strains to urinate, but it will be unable to do so or pass tiny drops of blood-tinged urine. Females rarely develop a blockage, but it does occur.
For cats over 10 years old with FLUTD, more than half will have a concurrent bladder infection and some degree of kidney dysfunction. Therefore, while extensive testing for a cause of symptoms may not yield results in younger cats, older cats with FLUTD should be screened for kidney failure.
Idiopathic cystitis describes a chronically inflamed bladder with an unknown cause. Cats may strain, urinate outside of the litter pan, and pass blood. No infection is associated with this condition.
When a cat presents with any of the symptoms listed above, a urinalysis is performed to categorize the type of urinary tract disease. Cells found in the urine sediment can allude to a bacterial infection as a primary or secondary factor. Antibiotics are prescribed any time a large number of white blood cells, the cells that fight infection, are observed. Sometimes, bacteria are obvious under the microscope. In this case, a culture and susceptibility should be run to determine the type of bacteria present and whether it has any antibiotic resistance. Most cats with FLUTD will have a large number of red blood cells present on urinalysis. Blood may be obvious to the owner, or it may be occult, revealed only on microscopic examination. X-rays and/or ultrasound of the urinary tract may be performed on all symptomatic cats to rule out bladder stones. Bladder stones are less common in cats than in dogs, but if they are present, symptoms will not resolve until they are removed surgically or dissolved with special diets. A chemistry panel, blood count, and electrolytes may be checked to discover other illnesses that may contribute to FLUTD.
Treatment for feline lower urinary tract disease depends on what is found during diagnostics. For the cat without infection, antibiotics are pointless. Cats diagnosed with idiopathic cystitis may be started on one or a combination of various medications which may include pain medications, antidepressants, and/or glycosaminoglycans. The exact mechanism by which these drugs work is unclear. Many cats respond well to amitriptyline, a tri-cyclic antidepressant that is given orally once or twice daily.