Feline Cystitis and Bladder/Kidney Stones
|Written by Lisa A. Pierson, DVM|
|Tuesday, April 28, 2009 11:38 AM|
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Cystitis and stones are extremely common in the cat and can be very painful and life-threatening. Cystitis can lead to inappropriate urination — urinating outside of the litter box — and stones can cause a fatal rupture of the bladder by blocking the outflow of urine.
Any cat that is repeatedly entering the litter box but not voiding any urine is in need of immediate medical attention. It is important to note, however, that "crystals" are not the same thing as stones. Crystals are often a normal finding in a cat's urine and it is not appropriate to put the cat on a "special urinary tract" formula when these are found in the urine.
Important: I often see too much clinical significance placed on the identification of crystals in the urine without regard to how the urine sample was handled. It is very important to understand that crystals will often form once outside of the body within a very short period of time, as little as one hour. If the veterinarian does not examine the urine right away and either sends it to an outside laboratory or uses a free-catch sample that the owner brought from home, an erroneous diagnosis of crystals may be made. This is called a "false positive" report and results in unnecessary worry on the part of the owner and often leads to the cat being placed on an inappropriate diet.
With regard to overall kidney and bladder health, I cannot stress strongly enough how important water, water, water is in both the prevention and treatment of diseases involving this organ system.
When a cat is on a diet of water-depleted dry food, they produce a more highly concentrated urine, with higher urine specific gravity, and they produce a lower volume of urine which means that a higher concentration of crystals will be present in the urine. This increases the chance of these crystals forming life-threatening stones. The concentrated urine and the lack of volume production can also be very irritating to the lining of the bladder wall predisposing them to painful cystitis.
Please keep in mind that a cat has a very low thirst drive and is designed to get water with their food. A diet of canned food will keep a proper amount of water flowing through the urinary tract system and help maintain its health.
Urine pH is also often considered when discussing urinary tract problems but we really need to stop focusing on pH. Again, a proper amount of water in the diet is the important issue here - not urine pH. Many of the so-called feline lower urinary tract diets are formulated to make the urine acidic but it is thought that these low magnesium, acidifying diets may actually exacerbate painful cystitis. Also, these acidifying diets, which are so often prescribed, may end up promoting calcium oxylate stones and hypokalemia.
It is also important to note - for those people still stuck on worrying about the urine pH - that there are many factors which determine the pH of urine and only one of them is diet.
With regard to dry food and urinary tract health, aside from the lack of water in this type of diet, there is also a correlation between the consumption of a high carbohydrate diet and the formation of struvite crystals as shown by a study published in February 2004 in the American Journal of Veterinary Research. Veterinarians often prescribe Science Diet® dry c/d® and x/d® for urinary tract problems but again, these diets are only ten percent water and contain a high level of species-inappropriate ingredients and questionable preservatives. They are also very high in carbohydrates with dry c/d® containing 42 percent of its weight as carbohydrates. Please note the first few ingredients in c/d while remembering that your cat is a carnivore:
Brewers rice, chicken by-product meal, corn gluten meal, pork fat (preserved with mixed tocopherols and citric acid), chicken liver flavor, taurine, preserved with BHT and BHA.
Diet is not the only issue involved with cystitis but it is an important one and one that we can control. Stress is also thought to play a very significant role in cystitis and even cats that are fed a 100 percent canned food diet may experience bouts of cystitis. This is a very frustrating disease to deal with and one that the veterinary community does not have all the answers for. What we do know is that decreasing stress and increasing the water content of the diet are the most important management issues to address. The water content of the diet is easy to control. The stress issue is another matter and is not always easy to address since cats can be very sensitive and are often "silent" in their stress.
Cystitis can be extremely painful and it is very important to address pain management in these cats. Remember pain = stress and we are trying to minimize the stress in these patients. Buprinex® is a good choice for a pain medication. This is superior to Torbugesic® which has been used for pain management in the cat in the past. Buprinex® is a prescription medication that you must get from your veterinarian. Unfortunately, many veterinarians overlook pain medications as a very important part of the treatment of this common feline problem.
A note on antibiotic usage in these cases. Most cases of cystitis are sterile. In other words, they are not the result of an infection and should not be placed on antibiotics.
Only ~1% of cats with cystitis that are under 10 years of age have a urinary tract infection, yet many veterinarians place these patients on antibiotics when these drugs are not warranted. Most cats under 10 years of age produce a very concentrated urine — USG greater than 1.030 — and bacteria do not grow well in concentrated urine.
In cats over 10 years of age, infections are more common but that still does not mean that older cats with cystitis should automatically be put on antibiotics. The reason that an older cat is more prone to urinary tract infections is because kidney disease is more common in this age group and so these cats will have a more dilute urine which is not as hostile to bacterial growth. Diabetes is also more common in cats over 10 years of age and diabetes makes a cat more prone to urinary tract infections.