We have all heard of how excruciatingly painful kidney stones are in humans, imagine how painful and frightening this condition must be to a dog that cannot explain what he or she is feeling. Cystinuria is a congenital genetic defect, which means that puppies are born with the condition but it may not become developed until the puppies mature. That is not to say the puppies may not have trouble with kidney stones even at a young age, it will vary greatly from dog to dog. Factors such as overall health, other presenting genetic or congenital problems or even kidney and bladder infections can make this situation more problematic at younger ages. Breeds that are known to have problems with kidney stones include Scottish Deerhounds, Mastiffs, Newfoundlands, Boxers, Cairn Terriers, Corgis and Labrador Retrievers.
Cystine is a naturally occurring amino acid produced by the dog's body. In normally functioning kidneys the cystine is filtered out of the urine in the tubules of the kidneys. When the tubules allow the cystine to get into the urine, it causes the formation of lumps of hard crystals that from kidney stones. This hard material can be small or large and can either fully or partially block the passage of urine through the urinary system. It is often most problematic in males but can occur in females as well. Not all dogs with cystinuria will actually develop kidney stones or deposits that are problematic for the dog. If stones do form and are blocking and restricting the movement of urine out of the body the results can be fatal.
Symptoms of kidney stones or cystinuria in dogs include painful and frequent attempts to urinate, blood in the urine and a very foul "rotten egg" smell to the urine because of the high cystine levels. The dogs may become very despondent or walk with their backs arched since the pain is localized in the kidney area. Vets can do a simple urine test to look for any trace of the amino acid cystine in the urine.
Treatment can include several different options. If the dog is diagnosed with the condition but has no presenting conditions such as the kidney stones, problems with urination or signs of pain and discomfort a special diet that is very low in protein can help reduce the risks of stones occurring. Special supplements can also be used to buffer the urine and keep the cystine from clumping to form stones. In cases where stones have already occurred they will need to be surgically removed from the bladder to prevent possible obstruction of the urinary tract. When a blockage of the urinary tract has already happened a process known as hydropulsion can be used to push the stone back up into the bladder where it can be removed.
In cases where surgery is not possible there are some new drugs available that can be given to the dog to try to break down the stones. These drugs are rather risky and very expensive and are not typically advised unless there are no other options. In some males a surgical procedure is used to re-route the urinary tract to a small, surgically developed opening beside or just to the front of the scrotum, more like the female dogs urinary opening, to prevent the problem of stone lodging in the smaller urinary tube of the penis.