Urinary Calculi: Bladder and Kidney Stones

Just about all of us have heard stories of people "passing kidney stones". However, most of my clients are surprised when their pet is diagnosed with either kidney or bladder stones. Dogs, in fact, are quite commonly affected by the formation of stones in both their kidneys and bladder. The stones are composed of varying mixtures of minerals that accumulate within the urinary tract. The particular type of stone that forms is determined by several factors including diet, water consumption, breed predispositions, urinary tract infection and medical conditions that affect the pet's metabolism.

The most common symptom observed in patients is an increased frequency of urination. This may also be accompanied by straining to urinate, dribbling of urine or the passing of blood in the urine. These are symptoms that should be checked out by veterinary examination ASAP.

Male pets (canine and feline) frequently become partially or completely blocked when trying to pass the stones. A urinary blockage is a life-threatening emergency and requires immediate veterinary attention. The first x-ray image is a cat that was completely blocked with small bladder stones that had become wedged into the urethra. This cat required emergency catheterization to relieve the obstruction and surgery to remove the stones. The second x-ray is a dog with numerous bladder stones in the bladder and a large accumulation of stones in the urethra at the base of the penis. This dog also required emergency catheterization and surgery to relieve the urinary obstruction.

The most common type of bladder stones are known as "Struvite". These typically form in response to a bladder infection and are most commonly found in female patients. This type of stones can be dissolved with special prescription diets fed over a period of several weeks coupled with long term antibiotics to resolve the underlying infection. Unfortunately, not all patients are candidates for dietary dissolution and surgery is required to resolve the problem. Following surgery or dietary dissolution, modifications in the pet's diet can usually prevent the formation of new stones.

The seond most common type of stones are composed of calcium oxalate. These cannot be dissolved and must be surgically removed in all cases if the problem is to be resolved. There are no diets available to reliably prevent the formation of new calcium oxalate stones. However, with proper dietary management and the use of appropriate medications we can decrease the chances of new stone formation.

The photos are from 4 different cases that required surgical removal of the stones. The top and bottom pictures are two variations of calcium oxalate stones. The middle two pictures are struvite stones.

Other types of bladder stones may be formed due to liver disease and metabolic disorders. Occasionally we seen bladder stones being formed due to a pet being fed an inappropriate diet.

Certain breeds of dogs are notorious for forming bladder stones. Most notably these include the Schnauzer, Bichon Frise and Dalmation breeds. However, all dogs and cats are at risk.

If your pet shows any signs of urinary problems (urinary accidents, increased frequency of urination, straining to urinate, passing blood in the urine or change in urinary odor), have your pet examined as soon as possible. Insist on a urinary ultrasound exam or x-ray to rule-out this potentially life-threatening problem.