Feline lower urinary tract diseases ("FLUTD")...formerly known as "FUS"...are either:
1) Obstructive or 2) Non-Obstructive:
In the obstructive form, more commonly observed in male cats, the narrow pathway from the urinary bladder to the external world, the urethra, contains proteinaceous or crystalline or mineralized solid or semi-solid material which impedes (i.e. "obstructs") the flow of urine. Urine produced by the kidneys accumulates in the bladder; the bladder becomes distended, inflamed and painful. The ensuing pressure from urine retention negatively affects the kidneys and can result in rupture of the bladder. Toxins, metabolites and electrolytes normally cleared by urine voiding may accumulate in the blood. Animals are sick, painful, noticeably distressed and if able, strain to urinate in or out of the litter box. This condition is potentially life-threatening and requires immediate veterinary intervention!
Infection:.... In some instances, lower urinary tract infection can precipitate subsequent development of FLUTD. However , in cats infection can also develop secondarily to ongoing FLUTD
Stress...may play a role in the development of FLUTD, though exactly how it contributes is not yet clear.
Allergy...is postulated to sometimes affect bladder wall mucosa and result in inflammation. Allergen may include food(s) and environmental sources.
Diet.... A dietary role has been postulated, in part based upon the decrease in the incidence in this syndrome since the introduction of specially formulated ("prescription") diets over the last decade or so1,2,3. Additionally, retrospective studies several years ago at The Ohio State University Veterinary School suggest that cats eating kibble diets are more likely to develop FLUTD than cats consuming canned (moist) diets
Gender and/or age of neutering.... have also been suggested as contributory factors: The relatively narrow lumen of the male cat urethra (compared to the female counterpart) possibly predisposes to obstruction. However, there is no evidence supporting the view that early (prior to puberty) neutering retards the development of the urethral diameter in any way leading to or exacerbating the liklihood of obstruction.
In non-obstructive lower urinary tract diseases, clinical signs depend upon the underlying cause(s):
Signs of voiding urgency, frequency and discomfort and voiding in inappropriate places are hallmarks of this type of non-obstructive lower urinary diseases. This differs from the obstructive form in that the bladder is small and contains little urine (even though "the urge" to urinate is marked) and...urine flows normally through the urethra. Males and females are both affected. Causes, and laboratory findings are similar to the obstructive form; treatment principles are the same (but relief of an obstruction is obviously unnecessary). Of the non-obstructive types of FLUTD, this form occurs in a minority of affected cats.
This is the most common form of non-obstructive lower urinary tract disease! The cause(s) is unknown but in humans with this disease, it is thought that the immune system is "reacting" to (or "attacking") the lower urinary tract and this phenomenon causes painful inflammatory lesions to develop in the bladder wall (i.e.this is an "autoimmune" disease). The vast majority of cats are presented for inappropriate urination but usually there is no sign of urgency, increased frequency or any other indications of a medical problem. Indeed, urinalysis is usually normal and urine is sterile (occasionally one may see a small amount of blood). Unfortunately these animals are frequently misdiagnosed with behavioral urinary incontinence (they are thought to have a psychological "issue"). There is, however a medical problem! Clues that a medical problem exists, if present, are subtle and may include an area of the abdomen where hair has been chewed (perhaps a futile attempt to "relieve" discomfort in the area) or "verbal" or physical indication that the abdomen is painful when touched. Historically, most (>75%) of cats with this type of disease consume either exclusively or predominantly dry food! The composition of the dry diet does NOT matter. This means that even cats placed on prescription diets are suseptible.
Diagnosis ...These type II- affected cats have Idiopathic (Interstitial) Cystitis (this means the bladder is inflamed and the cause is unknown); this condition is an all too common occurence in humans..especially women. It is now being recognized with increasing frequency in our pet cats...male and female individuals. Diagnosis is extremely difficult without either special instruments (urethrascope/cystoscope) or surgical exploration and biopsy of the bladder. Simple and special (contrast) x-rays, though helpful can provide only a presumptive diagnosis. When bladder wall is viewed by either of the aforementioned special techniques, a unique inflammatory/hemorrhagic pattern is observered (called "glomerulations")..which is considered diagnostic of the syndrome.
Treatment.... Available data suggests that a moist diet should be fed to these cats. If a cat will only eat kibble then moistening this as well as encouraging additional water consumption may also be beneficial. In addition, some advocate use of the antidepressant, amitriptylline (Elavil®), though there is no scientific data authenticating its efficacy. It is postulated that (in theory) this drug relieves bladder inflammation and pain by acting as both a potent antihistamine and also as an antispasmodic and that, psychologically, it may diminish some anxiety associated with the condition (and reduce stress).
Some are advocating glycoseaminoglycan ("gag") therapy as well. In human interstitial cystitis, these molecules appear to be deficient in the bladder lining, possibly allowing urine to seep into and irritate sensitive bladder tissue. The drug Elmiron ® has been approved for precisely this purpose in humans. Whether this is an important therapeutic option in veterinary medicine is unclear at this time, but several veterinarians are reporting, anecdotally, some positive effects of Elmiron ® .
In addition to these possible remedies, a few cats will benefit from some form of pain management. At a recent veterinary meeting (TNAVC 2004) data were presented showing that the use of oral butorphanol seemed to make some cats more comfortable (though it had no positive benefit on the intensity nor the progression of bladder inflammation).
Finally...and most importantly...most FLUTD-affected cats will go into (and out of) remission periodically whether we intervene or not!
Special Notes on Prescription Diets
1. Previously there was a strong belief that high magnesium content contributed to the occurence of FLUTD; however, some magnesium salts, by virtue of their ability to make urine more acid, are actually beneficial for certain types of urinary tract crystal and stone dissolutions.
2. Some prescription diets, while helpful in medically dissolving certain stones and crystals, may actually increase the probability of other types of stone formation that can NOT be dissolved medically.
3. Diets advertised "...to promote urinary tract health" SHOULD NOT to be fed to animals with upper urinary tract (i.e.kidney) disease, as such feeding will worsen the liklihood of the progression of renal disease to renal failure! There are other prescription diets specifically formulated to help with the management of kidney disease.
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