Dog Bladder Stones

Oxalate Bladder Stones (canin)

* 73% of calcium oxalate patients are male. This stone type is unusual in females * Breeds at especially high risk include: miniature schnauzers, lhasa apsos, Yorkshire terriers, miniature poodles, shih tzus, and bichon frises * Most cases occur in dogs between ages 5 and 12 years

How do we know there are calcium oxalate stones? Although a urinalysis can provide a clue, the only way to know for sure that a dog's bladder stone is an oxalate stone is to retrieve a stone and have a laboratory analyze it. If the stones are very small, flushing the urinary bladder and forcefully expressing it may produce a stone sample for testing. The only other way to obtain a sample is to surgically open the bladder and remove the stones. The surgical method is invasive but provides the most rapid resolution of the bladder stone issue. Calcium oxalate stones cannot be made to dissolve over time by changing to a special diet (as can be done with struvite or uric acid bladder stones).

Why would my dog form calcium oxalate stones? It should not be too surprising that there is a strong hereditary component to the formation of oxalate bladder stones. This is also true in humans. There is a substance (called nephrocalcin) in urine that naturally inhibits the formation of calcium oxalate stones. This substance is defective in both humans and dogs who form calcium oxalate bladder stones. The production of defective nephrocalcin may be a genetic problem.

In humans, the genetic predisposition for stone formation is coupled with dietary issues (problem foods include: spinach, peanuts, chocolate, dairy products, calcium supplements, vitamin C supplements, and tea). Dogs are more likely to eat simply a commercial brand of dog food without nearly the dietary variety that humans experience. This means that diet can be used to manage the problem in the dog but, unless the dog is receiving an unusual treat supply, probably the diet is not a cause.

Why can't the stones stay where they are? The most immediate concern for the dog with bladder stones is that the urinary opening may obstruct as the dog attempts to pass the stones. This is largely a male dog problem but the results can be life-threatening uremic poisoning. In such cases, the veterinarian will try to dislodge the stone, flushing it back into the bladder to restore the patency of the urinary opening. If the stone cannot be dislodged, a new urinary opening may have to be surgically created. The urethra (the narrow tube connecting the urinary bladder to the outside world) is a difficult place to perform surgery so it is preferrable to move the stone back into the bladder for removal rather than attempting removal from the urethra.

Bladder stones are irritating to the bladder simply by rubbing on the tender bladder lining. Bleeding typically results and, of course, the chance of developing chronic bladder infections is markedly increased with the presence of bladder stones.

Because calcium oxalate stones cannot be dissolved by diet change, surgical removal of the stones is usually necessary.

Studies have shown that 50% of dogs that have undergone such surgery will develope new3 calcium oxalate stones within 3 years.

The following tehrapeutic plan has been devised to minimize the chance of recurrance: BR>
STEP ONE: DIET While special diets cannot dissolve existing stones, they do help prevent the development of new stones. Prevention centers on creating a urinary environment with minimal calcium and minimal oxalate as well as creating a urine pH that is not conducive to calcium oxalate formation.

The usual diets recommended include:

* Hills K/D diet * Hills U/D diet * Select Care Modified diet * CNM NF from Purina * Waltham's Low Protein Diet

For each of the above diets, the canned form is preferrable to dry so as to increase water consumption and thus help dilute the urine. It is especially important to avoid table scraps when caring for an oxalate stone forming dog. Still, no one wants their dog to live life without treats. The following treats are acceptable for oxalate stone-forming dogs: plain cooked chicken, plain cooked turkey, eggs, rice, popcorn, peas, and pasta.

Many pet owners ask if any non-prescription diets are appropriate for this condition. None are.

There are some medications which can increase the risk of calcium oxalate stone development and these should be avoided. Prednisoneand other cortisone-type medications (commonly used for itchy skin, arthritis, inflammatory bowel disease, and other inflammatory conditions) should be avoided if possible. Furosemide(brand name: Lasix) is a diuretic mostly used in the treatment of heart failure. It also leads to excess calcium in urine. Should a diuretic be needed for a patient at risk for calcium oxalate stones, one from the thiazide class (see later) would be a better choice. Supplementation with Vitamins D or C also increase risk of forming oxalate stones; such supplementation should be discontinued.

STEP TWO: Urinalysis Two to four weeks after surgery, a urine sample is checked. If the urine is not adequately dilute, water consumption will have to be increased (either by adding water to the food or increasing the amount of canned food).

If urinary pH is less than 6.5 or if oxalate crystals are seen, it is time to go to Step Three. If all is well, a urinalysis should be performed every 2 months or so for the rest of the dog's life (University of Minnesota's current recommendation).

Radiographs are taken every 3 to 6 months so that any new stones will still be small enough to be retrieved from the bladder by flushing. If one skips this monitoring, one may find stones present have developed to a large size and surgery is again needed to remove them.

STEP THREE: Potassium Citrate. By taking potassium citrate orally, citrate levels increase in the urine. Calcium binds to citrate instead of to oxalate which is a desirable event since calcium citrate tends to stay dissolved whereas calcium oxalate tends to precipitate out as mineral deposit. Potassium citrate also helps create an alkaline urine (in which calcium oxalate stones have difficulty forming). Potassium citrate supplements are typically given twice a day.

STEP FOUR: URINALYSIS Two to four weeks after diet change, a urine sample is checked. If the urine is not adequately dilute, water consumption will have to be increased (either by adding water to the food or increasing the amount of canned food).

If urinary pH is less than 6.5 or if oxalate crystals are seen, it is time to go to Step Five. If all is well, a urinalysis should be performed every 2 months or so for the rest of the dog's life (University of Minnesota's current recommendation). Again, radiographs should be taken every 3 to 6 months.

STEP FIVE: THIAZIDE DIURETICS A diuretic is a medication designed to increase the amount of urine produced. The thiazide class of diuretics does this in a way that reduces the calcium content of the urine. This medication is typically given twice a day and electrolytes are generally measured via blood test within the first 2 weeks of this treatment.

There will always be some dogs who continue to form stones no matter what is done. With radiography monitoring, it is hoped that new stones can be detected while they are still small. As research continues, it is possible that new developments will arise that will not require such frequent monitoring. Until then, these are the guidelines for oxalate prevention as proposed by the specialists at the University of Minnesota.

The above is general veterinary information. Do not begin any course of treatment without consulting your regular veterinarian. All animals should be examined at least once every 12 months.

About the author:

Copyright 2002 - 2006 by the Veterinary Information Network, Inc. All rights reserved.

Linda Mar Veterinary Hospital and its cat-only affiliate, Coastal Cat Clinic, are small animal practices located in Pacifica, California. To find a veterinarian or to learn more about the vet clinic and our staff, visit:[ Other Articles You Might Enjoy:

The History Of The Yorkshire Terrier Although the history of the Yorkshire Terrier is sketchy, there is a great deal known about the origins of this exceptional, vibrant breed. The Yorkshire Terrier, or Yorkie for short, finds it humble beginnings in Northern England, in the counties of Yorkshire, Manchester and Leeds, during the years prior to 1750. During this time, the onset of the Industrial Revolution gave rise to small communities located around coal mines, textile mills and factories. The people of these areas originally made their living from the land and experienced great upheaval during the time of the Industrial
Click here to read the rest of this article ...

A Step-By-Step Guide To Puppy PickingWith hundreds of breeds to choose from, how do you decide which one is right? Narrow down the choices in a few simple steps. Size Matters First, consider your available space. If you live in an apartment, you can rule out large dogs. Look for dogs in the Toy group, such as Yorkshire Terriers, or some of the smaller dogs in the Terrier group, like the Miniature Schnauzer. If you have children, you may want to rule out very small dogs, such as Chihuahuas or Maltese. They are delicate and can be accidentally injured by young
Click here to read the rest of this article ...