1500 East Boston Post Road o Mamaroneck, NY 10543

Judith S. Johnessee, MS, DVM
Diplomate, American College of
Veterinary International Medicine


Feline Urinary Tract Problems

Both male and female cats can develop cystitis, which you the owner usually notice because of changes in litter box behavior. Instead of a few trips to the box a day, your cat is continually in and out of the box, passes only a few drops of urine at a time, vocalizes and is restless, and may urinate outside the box on newspapers, clothing, or in the tub or shower. The urine can look grossly normal or can be overtly bloody, but usually contains at least microscopic traces of blood. Since male cats have a very narrow urethra where it passes through the penis, the blood and mucus can cause a complete obstruction which can be a life-threatening problem. If this happens, he will not be able to pass even a few drops of urine, his bladder will become very enlarged and painful and he may cry out when picked up, and he will stop eating, become extremely depressed, and may vomit. If this occurs, he must be seen by a veterinarian immediately -- he cannot wait until the next day or he might die. Females with their larger urinary openings rarely obstruct, but it is possible and the same serious symptoms of loss of appetite, vomiting, and significant distress are present.

The cause of cystitis in cats is not completely understood at the present time. Rarely, it can be due to a bacterial infection of the bladder, and although this is not the most common cause, it needs to be ruled out by urine analysis and culture. Although other factors like stress and things which promote urinary retention like obesity and dirty or inaccessible litter boxes and even certain viruses have been implicated, the current theory is that the dietary magnesium level is one of the most important variables. Ash content is actually magnesium, calcium, and phosphorus, and some low ash foods are actually high in magnesium but low in dietary calcium, so simply checking the ash content of food is not helpful. Also, just feeding canned food and not dry does not guarantee a low magnesium diet as some dry foods are actually lower in magnesium than some canned foods. Thus the recommendation that male cats should not eat dry food is an old wives tale. It is the magnesium level of the total diet which is important. As mentioned earlier, magnesium is probably not the entire story and some cats can tolerate more magnesium in their diet than others, so you have to see what works for your individual cat. There are a wide variety of low magnesium foods available now, but some require the addition of acidifiers and some are available only through pet stores or veterinarians. You and your cats will decide what works best for you. Generally it is much easier to feed all the cats in the household the same thing even though they may not all be affected.

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