Bladder Stones (Urinary Stones)
Bladder stones are a common cause of urinary signs in dogs, cats, and small mammals (rabbits and guinea pigs).
What is a bladder stone?
A bladder stone is a stone composed of crystals that form inside the urine of the animal. These stones are commonly made up of magnesium ammonium phosphate (or struvite) crystals or calcium oxalate crystals. There are other, less common, components including calcium phosphate, cystine or urate crystals. Depending on the composition of the stone, some stones are smooth and round, while others are rough with projections on them.
What causes stones to form?
Stones form because of an ideal growing environment inside the bladder. The contributing factors are the pH (level of acidity) of the urine, presence of a urinary tract infection, dietary factors, and genetic predisposition.
What are the signs of my pet having a bladder stone?
Most owners notice signs of urinary discomfort in their pet. These signs include: blood in the urine, straining to urinate (squating or posturing but very little urine comes out), accidents in the house or outside the litter box, or increased frequency of urination. Your pet exhibits these signs because the stone can rub against the wall of the bladder, causing discomfort and irritation. The bladder wall may shed blood into the urine from this irritation. Additionally, many animals have concurrent urinary tract infections and the bacteria inside the bladder can lead to discomfort as well. Sometimes urinary stones can be an incidental finding, meaning that they were found inside the bladder on an x-ray but are not currently causing any issues.
How is a bladder stone diagnosed?
The best way to diagnose a bladder stone is though an x-ray or ultrasound. These imaging techniques also us to visually observe the bladder and determine the size, shape, and number of stones. Sometimes crystals can be seen on a urinalysis test (an examination of the urine under the microscope), but not always.
How is a bladder stone treated?
When stones cause urinary discomfort in animals, the best treatment is to have them surgically removed. If a bladder stone is present but not causing urinary discomfort, certain stones (those made up of struvite crystals), may be amenable to medical dissolution with a special prescription diet.
Are some pets more predisposed to urinary stones?
Yes. For example, because of the physiology and metabolism of small mammals, many guinea pigs and rabbits are predisposed to developing bladder stones or sludge (sand) inside their bladders. Furthermore, certain breeds of dogs including Bichon Frises, Yorkshire Terriers, and Miniature Schnauzers are genetically more prone to developing stones. Additionally, if an animal has a history of stone formation, they are more likely to redevelop stones in the future.
