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Feline lower urinary tract disease (FLUTD) is a broad term that is used to cover a number of conditions associated with the feline lower urinary tract. It may present as any of a variety of problems such as, inflammation of the bladder (cystitis) or urethra, formation of urinary crystals/stones in the bladder (crystalluria/urolithiasis), and partial or total obstruction of the urethra. The latter condition is also known as plugged-penis syndrome. Complete urethral obstruction is fatal if left untreated.
FLUTD is a common disease in adult cats, affecting from 0.5% to 1% of the population. FLUTD affects cats of both sexes, but tends to be more dangerous in males because they are more susceptible to blockages due to their longer, narrower urethrae. Urinary tract disorders have a high rate of recurrence, and some cats seem to be more susceptible to urinary problems than others.
The older term, Feline urologic syndrome (FUS) was renamed to discourage the perception that the clinical signs seen represent one disease with one cause.
Approximately 15-20% of FLUTD cases are caused by uroliths, with the most common form being calcium oxalate and struvite (magnesium ammonium phosphate) uroliths. The majority of uroliths are located in the urinary bladder, but can also form in the kidneys, ureters and urethra.
Many studies have concluded magnesium in the diet as a primary cause of struvite urolithiasis in cats. However, researchers have found that urine pH is a more important contributing factor. Urine that is acidic helps to dissolve struvite uroliths and also provides a less favourable environment for its formation. Commercial feline diets now limit the amount of magnesium and add acidifiers in the food to increase urine acidity, thereby reducing the likelihood of struvite formation. The decrease of struvite uroliths coincides with an increase in oxalate uroliths, low magnesium levels and urine pH both being a factor in calcium oxalate formation. Oxalate uroliths are not dissolvable in cat urine and have to be removed surgically, barring those small enough to pass out the urinary tract.
Less common forms of uroliths includes ammonium urate, uric acid, calcium phosphate, and cystine uroliths. Urine acidification has been induced in felines by using ethylenediamine dihydrochloride, DL- methonine, ascorbic acid, ammonium chloride, calcium chloride phosphoric acid, and sodium bisulphate. Increasing dietary phosphorus has been shown to reduce the excretion of magnesium in urine, but if a higher phosphorus diet has been administered with a high magnesium diet, formation of struvite crystals may occur if the pH of the urine is not low enough. Further supplementation may come from administrating glucosamine to the feline, though this may not be enough to reduce cystitis of the bladder.
Urine pH can be made more acid by increasing protein intake from animal and fish sources. Examples include human table scraps such as beef (steak/hamburger) and fish. Low cost urine test for humans can be used for monitoring and verifying that a cat's pH is below 6.8. A syringe can be used to suck up the urine from the floor when a cat urinates inappropriately and then squirted onto the test strip.
A complete urethral obstruction can happen suddenly and is life-threatening, therefore immediate treatment is necessary. A combination of crystal precipitates (most typically struvite uroliths) and protein matrix (mucus or blood cells) can form a urethral plug and cause a complete blockage of the urethra. Inflammation of the bladder wall can cause the protein matrix to "leak" from the wall. Even without crystal formation, a thick protein matrix may cause urethral obstruction by itself. Renal failure and uremia will follow within 36–48 hours of complete urethral obstruction. The time from complete obstruction until death may be less than 72 hours.
Bacterial infection is a very rare cause of FLUTD, accounting for 1-5% of cats younger than 10 years.
Other conditions that can contribute to this disease include physical trauma, tumors of the urinary tract, intentional urinary retention (a common behavior seen in cats not given a suitable place to void (e.g. no litterbox or dirty litterbox)), congenital abnormalities and neurological problems. In about 60% of cases, the cause is never discovered. These are classified as idiopathic FLUTD cases or Feline Idiopathic Cystitis(FIC).
GP-51, a specific glycosaminoglycan, lines healthy bladders of felines, where it prevents bacterial adherence and protects the bladder from the toxic properties of urine. Cats with interstitial cystitis (internal link), or inflammation of the bladder, excrete lower amounts of GP-51 along with other glycosaminoglycans, leaving the lining of the bladder exposed. Substances from the urine contact sensory neurons in the bladder, causing pain and neurogenic bladder inflammation. The sensory neurons are composed of unmyelinated C-fibers (group C nerve fiber), and when stimulated cause pelvic pain. Prolonged stimulation of the C-fibers causes chronic inflammation that is maintained through the release of the neurotransmitter, substance P. This increases the vascular permeability of the bladder, allowing red blood cells and lymphocytes to enter.
The disorder may be caused by a combination of these factors. For example, a diet which is high in magnesium or other minerals and high in pH, combined with inadequate intake of water may lead to favorable conditions for precipitating buildup in the lower urinary tract. However, these factors affect individual cats differently.
The locus coeruleus (LC) and the paraventricular nucleus in afflicted cats have been found to possess higher levels of tyrosine hydroxylase immunoreactivity, suggesting that these brain sites may be areas of high catecholamine synthesis. Consistent with this, elevated levels of catecholamines have been found in afflicted cats both at rest and during high stress situations as well. Desensitization of α2-adrenoceptors found in the LC, spinal cord, and bladder mucosa have been found in felines with FIC. α2-adrenoceptors normally regulate the flow of blood to the bladder and inhibit catecholamine release and pain perception to the brain. Chronic stimulation yields desensitized receptors and may lead to potent inflammatory responses in FIC felines. Felines with FIC also have abnormalities in corticotropin stimulation and larger adrenal medullary areas, suggesting that they are susceptible to over stimulation to the sympathetic nervous system.
Regardless of cause, there are a common set of symptoms, which includes frequent trips to the litter box (pollakiuria), prolonged squatting and straining during attempts to urinate (dysuria), small amounts of urine voided in each attempt, blood in the urine (hematuria) and urinating outside of the litter box. Owners with outdoor cats may not be able to observe the symptoms associated with litter box use and should watch for unusual behavioral changes.
A cat experiencing a urethral obstruction behaves similarly to any other cat with FLUTD. However, as time passes, the bladder fills up with urine and cause painful bladder distension. Kidney failure and uremia will follow within hours. The cat becomes increasingly distressed, and may howl or cry out in pain. The male cat may constantly lick at his penis and the penis may be protruded. The cat may seek seclusion, stop eating and drinking, begin to vomit, and become lethargic and eventually comatose as toxins accumulate in the bloodstream.
Urethral obstruction is a serious medical emergency which will lead to death if not treated in time. Any cat suspected of suffering from this condition should be seen immediately by a veterinarian.
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A blocked urethra is a life-threatening medical emergency that requires immediate veterinary attention. If the bladder cannot be emptied, it can reach capacity and inhibit kidney function resulting in Renal failure. This will cause kidney damage, thus it is important that treatment begins as soon as possible. The plug must be removed from the penis and the bladder drained. Gentle mechanical manipulation of the penis may dislodge the blockage, or a catheter might be used to drain the bladder. Intravenous fluids are given to treat uremia. Antibiotics and a special diet may be prescribed. Diets low in magnesium and urine acidifiers may be helpful. Cats susceptible to repeated attacks of this disorder may require surgery, such as the removal of the penis (Urethrostomy) to prevent its blockage.
Cats with chronic feline lower urinary tract disease caused by struvite crystals or oxalate crystals can be treated with a lifelong diet of a prescription wet or dry food which minimizes the content of the building blocks of the crystals. These foods will be prescribed by vets if needed and will replace all other food to ensure a healthy urinary tract. Even after treatment, cats need to be checked regularly for urinary problems as the crystals can return.
Cats with LUTD and especially those with reoccurring FIC may benefit from environmental enrichment. Environmental enrichment includes changing of the type of litter used and maintaining a clean area for the litter boxes. The “1+1” rule for multiple cat owners is highly advised, where the house has a litter box for each cat they own, plus an additional one. If cats have urinated outside of the litter box in inappropriate places, thorough cleaning of the area is advised to reduce the interest of other cats. Placing litter boxes in areas of low noise and traffic and away from other pets is also suggested.
Mimicking natural behavior for a cat with chronic stress helps them relax. They benefit from “hide and seek” games with their food, where they are “hunting” in their environment. Placing scratch posts or raised walkways where they can retreat and hide increases their sense of security and familiarity of the area. The use of laser pointers and toys to increase their exercise levels is also advisable, as obese and sedentary cats seem to be at higher risk for the development of LUTD and FIC.
Cats that are particularly sensitive to their environment require a strict routine with minimal environmental changes. For instance, owners can inadvertently stress their cats out with their own emotional displays or changes in their routines. The use of simulated feline facial pheromone can reduce the activation of the sympathetic nervous system and reduce stress through a sense of familiarity. Lastly, anti-inflammatory drugs such as carprofen may be prescribed to reduce pain. Amitriptyline, an antidepressant, has also shown benefits but needs further research.
Carlson, Delbert G. & Giffin, James M. Cat Owner's Home Veterinary Handbook. New York: Howell Book House, 1995.