Bladder stone (animal)

The stones form in the urinary bladder in varying size and numbers secondary to infection, dietary influences, and genetics.

Smaller stones may become lodged in the urethra, especially in male animals, causing urinary tract obstruction and the inability to urinate.

Oversaturation of urine with crystals is by far the biggest factor in stone formation in dogs and cats.

Other contributing factors include diet, frequency of urination, genetics, current medications, and the presence of a urinary tract infection.

[4] It is possible for the nidus to be made of a different type of crystal than the rest of the stone, also known as epitaxial growth.

Sodium, calcium, phosphorus and potassium ratios and quantities play a large role in urinary health of animals.

Research indicates that low dietary inclusion of potassium is associated with increased renal calcium excretion, which lowers urinary pH.

By feeding proper amounts of calcium and potassium we avoid this issue, which is especially common in male cats.

Bacterial infections contribute to their formation by increasing the pH of the urine through the urease enzyme in dogs.

Certain dog breeds are predisposed to struvite stones, including Miniature Schnauzers, Bichon Frises, and Cocker Spaniels.

Calcium oxalate stones form more readily in animals with hypercalcaemia, which can be caused by Addison's disease or certain types of cancer.

For prevention a diet low in protein and oxalates and high in magnesium, phosphorus, and calcium is recommended.

Prevention is through reducing calcium intake by feeding more hay and less commercial rabbit pellets, and by not using mineral supplements.

Urate stones form due to an increased excretion of uric acid in the urine.

Dalmatians (especially males)[13] and to a lesser extent Bulldogs are genetically predisposed to the formation of urate stones because of an altered metabolism of purines.

Feeding a diet high in purines while simultaneously administering allopurinol can result in the formation of xanthine (C5H4N4O2) stones.

Dog breeds possibly predisposed to calcium phosphate stone formation include Yorkshire Terriers, Miniature Schnauzers, and Cocker Spaniels.

There is possibly an increased incidence associated with dogs on diets that have a large amount of corn gluten or soybean hulls.

[3] Reasons for treatment of bladder stones include recurring symptoms and risk of urinary tract obstruction.

In male dogs with recurrent urinary tract obstruction a scrotal urethrostomy creates a permanent opening in the urethra proximal to the area where most stones lodge, behind the os penis.

Recurrent cases can be treated surgically with a perineal urethrostomy, which removes the penis and creates a new opening for the urethra.