term FUS (Feline Urological Syndrome or FLUTD...Feline Lower Urinary
Tract Disease) is a broad expression that covers cystitis or bladder
infections in the female and cystitis and urinary blockage in the male.
The most common feature of FUS is the presence of struvite crystals, which
consist of magnesium-ammonium-phosphate. Bacteria are often present...the
result and not the cause of FUS.
The ash content, and especially the magnesium content, of cat food was formerly thought to be significant in the production of struvite crystals, but recent experiments where excess magnesium was added to the food showed that this did not increase the incidence of FUS. FUS occurs almost exclusively in cats fed a diet, either partially or completely, of dry food. As many of you know, cystitis can be very annoying with the cats constantly trying to pass a few drops of urine, wherever they happen to be. However, urinary blockages can be fatal in males as the toxic wastes build up in the blood due to backpressure from the bladder into the kidneys, which can no longer filter out urine.
Cats are generally not big drinkers. They drink by rapidly dipping the tongue into a liquid and drawing it back into the mouth. The rough tongue holds some of the liquid. This is not a very efficient way to consume liquids. In the wild, cats get most of their water from their food and don't need to drink much. Horses and ruminants, which suck up water, are efficient drinkers because they need to be, given their diet of often-dry roughage.
Dr. Steven Tobin explains that cat's urine is quite concentrated under the best of circumstances. The cat's natural diet (meat) is about 75% water. That means that for every 1 part of solids (25% of the meat), the cat is taking in 3 parts of water (75% of the meat). Cats eating dry food (90% dry matter) therefore need to drink almost 3 times as much water as the food they are eating to obtain the same ratio of water to dry matter. Most cats, being such inefficient drinkers, seldom do this. Thus, the normally very concentrated urine becomes even more concentrated almost to super saturation, so that any little upset causes crystals to form. These crystals irritate the bladder walls, which allows bacteria to settle. The bacteria split urea to release ammonia which raise the pH of the urine allowing it to hold even less solutes in solution, so more crystals form causing more irritation allowing more bacteria, etc.
This irritation causes the cat to try to urinate continually. The lining of the bladder wall, being a mucous membrane, reacts as mucous membranes do and produces mucous. The combination of crystals and mucous can cause a plug in the narrow male urethra, blocking the outflow of urine from the bladder.
The best diet to feed a cat to prevent this is one consisting mostly of raw meat or poultry. Meat produces a lower urinary pH than plant material in the diet. This, along with the higher percentage of water, will help prevent crystal formation. Any cat that has had a bout of cystitis should be put on a raw meat diet, along with a small amount of food processed raw vegetables and supplements which include bone meal.
To confirm that FUS is correlated to lack of water, consider cats with chronic renal failure. These cats drink large amounts of water, as their kidneys cannot recycle the water passing through. Their urine is very dilute. How often have you seen one of these cats have FUS?
Further, plain water does not re-establish the proper electrolyte balance (sodium chloride, potassium, calcium). If your cat or kitten is drinking water but not eating, this condition often necessitates a trip to the vet for subcutaneous fluid therapy. Dehydration can be fatal.
If your cat is eating a dry food or canned commercial food diet, I recommend you convert to the raw food diet (which is outlined on my website, www.celestialpets.com, and in my book, Natural Cat Care) supplemented with my Celestial Pets® supplements. We have had incredible results over the past decade.