Feline lower urinary tract disease

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 and blocked cat 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.[1]
Causes
===[edit] Uroliths===
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.
===[edit] Diet===
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.[2][3] 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.[3] Urine acidification has been induced in felines by using ethylenediamine dihydrochloride, DL- methonine, ascorbic acid, ammonium chloride, calcium chloride phosphoric acid, and sodium bisulphate.[4][5] 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.[6] Further supplementation may come from administrating glucosamine to the feline, though this may not be enough to reduce cystitis of the bladder.[7]
===[edit] Urethral obstruction===
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.[8] 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.[9]
===[edit] Infectious causes===
Bacterial infection is a very rare cause of FLUTD, accounting for 1-5% of cats.
===[edit] Others===
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).
===[edit] Feline Idiopathic Cystitis===
GP-51, a specific glycosaminoglycan, lines healthy bladders of felines and is meant to prevent bacterial adherence and to protect 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
Category:Medical & Preventive Care