The most common cause of FLUTD in cats less than 10 years of age is non-obstructive
feline idiopathic cystitis. Less common causes are
urolithiasis, and urethral plugs which usually result when an attack of
feline idiopathic cystitis is not self-limiting and escalates into a blockage of the bladder (i.e. obstructive FIC). Urinary tract infections (UTIs) can also be a cause of FLUTD but are very rarely seen in younger/middle-aged cats. However, in cats over the age of 10, UTIs are more frequently seen, particularly in female cats. The rarest forms of FLUTD for any age/sex cohort include anatomic defects, behavioural disorders and
neoplasia.
Urolithiasis 15-20% of FLUTD cases are caused by
uroliths ("stones") which occur when crystals which may be present in urine coalesce to form small stones. The most common types observed are
struvite and
calcium oxalate. The majority of uroliths are located in the urinary bladder, but can also form in the kidneys, ureters and urethra. The underlying microscopic crystals which go on to form bladder stones are not on their own an abnormal finding. They are often found in well-hydrated healthy cats who simply flush them out with their urine. However, they can pose the risk of urethral obstruction if they accumulate in the bladder and are allowed to clump together to form larger stones (i.e. uroliths) which then become lodged in the urethra. Alternatively, they can coalesce with inflammatory bladder debris (or "matrix") to form obstructive
§ urethral plugs following an attack of
feline cystitis (see below). If the obstruction (whatever the cause) prevents urination altogether then it is a medical emergency which requires immediate intervention.
Causes Some studies have concluded
magnesium in the diet could be a primary cause of struvite urolithiasis in cats. However, researchers have found that concentrated urine (due to low levels of hydration) and
alkaline urine
pH are more important contributing factors. Increasing moisture intake via wet food is above all the most important preventative measure as it dilutes the urine which dissolves struvite crystals as well as encouraging urination to flush out any crystalline debris remaining in the bladder. Acidic urine also helps to dissolve struvite uroliths and discourages its formation. Commercial feline foods limit the amount of magnesium and add acidifiers such as DL-
Methionine to increase urine acidity, thereby reducing the likelihood of struvite accumulation. However, whilst acidic urine is associated with a decrease in struvite uroliths, excessive acidity can result in an increase in calcium oxalate uroliths, low magnesium levels and urine pH both being factors in calcium oxalate formation. Oxalate uroliths do not dissolve in cat urine and cannot be managed with diet. Less common forms of uroliths include ammonium urate, uric acid, calcium phosphate, and cystine uroliths. • ethylenediamine dihydrochloride • DL-methionine • ascorbic acid (
vitamin C) • ammonium chloride • calcium chloride phosphoric acid • sodium bisulphate but there always remains the risk of possible obstruction whilst waiting for the stones to dissolve. Increasing dietary
phosphorus can reduce the excretion of magnesium in urine; but, if a high phosphorus diet is combined with a high magnesium diet, and the urine pH is not low enough, struvite crystals may form. High phosphorus diets are contraindicated in cats with chronic kidney disease. Further supplementation may come from administrating
glucosamine to the feline, though this may not be enough to reduce cystitis of the bladder. Urine pH is also naturally made more acidic by increasing the meat/fish-based protein percentage in food. Cats with
chronic feline lower urinary tract disease caused by struvite uroliths are sometimes treated with a lifelong diet of prescription wet food as these special diets acidify urine which dissolve struvite. However ordinary wet food with high moisture content and rich in animal protein can be just as effective in many cases as it keeps the urine mildly acidic and dilute, both of which militate against struvite formation. Dry food of any sort should be avoided due to its low moisture content and possible dehydrating effects. Even after treatment, cats need to be checked regularly for urinary problems as the crystals can return.
Urethral plugs During an acute attack of feline idiopathic cystitis, the bladder experiences painful inflammation. This inflammation can cause a protein matrix to "leak" from the bladder wall. The
matrix is formed of material such as mucus and blood cells which can coalesce with crystal precipitates (most typically struvite) to form a urethral plug. A urethral plug can cause a complete blockage of the urethra and prevent urination. Even if there is no crystal formation, a thick protein matrix may cause urethral obstruction by itself though this is seen more rarely. Urethral plugs are described as "mechanical" blocks of the urethra. Signs include: • frequent trips to the
litter box (
pollakiuria) • prolonged squatting and straining during attempts to urinate (stranguria) • blood in the urine (
hematuria) • urinating outside of the litter box • no urine voided at all at each attempt or only isolated drops produced ("spotting") Confusingly, all but the last symptom can be also observed in cats who are suffering from "non-obstructive"
feline cystitis where a urethral plug has not in fact yet developed and the cat's urethra remains patent (i.e. open). These non-obstructive episodes usually resolve themselves in a week with good hydration,
analgesia and/or
anti-inflammatory medication together with anti-spasm drugs such as
prazosin. The key difference between the two types of episodes will be that a blocked cat will not be able to pass urine at all whereas the unobstructed cat will still be able to void, albeit in small, frequent amounts (i.e. urination is still possible but it presents abnormally). A vet will be able to distinguish between the two by
palpating the cat's bladder to see if it can be emptied without obstruction. Most episodes remain non-obstructive and do not progress to the formation of urethral plugs. Owners with outdoor cats may not be able to observe the symptoms associated with litter box use and should watch for unusual behavioural changes. If the cat is indeed blocked with a urethral plug, as time passes, the bladder fills up with urine and causes painful bladder distension. 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.
Treatment 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, causing kidney damage.
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. However, in cats over 10 years of age, UTIs are much more prevalent and
idiopathic cases much less frequent. Other FLUTD conditions include physical trauma, tumors of the urinary tract, voluntary urinary retention (a common behaviour 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). Cats with FLUTD 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 behaviour for a cat with chronic stress helps them relax. Since indoor cats are an at-risk cohort, supervised outdoor play for restricted periods will increase stimulation and reduce stress. They can also 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 play time and toys to increase their exercise levels is advised 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, pain medication such as
buprenorphine or
meloxicam may be prescribed to reduce swelling and pain during an acute flare-up of
cystitis and can assist recovery and provide relief to the cat. This should usually be taken for 7–14 days or until symptoms subside. Anti-spasm drugs such as prazosin may also be given to prevent painful urethral spasms which could escalate into a functional block.
Amitriptyline, an antidepressant, has also shown some benefits but needs further research. ==References==