Bladder Stones in Dogs and Cats
There are many types of bladder stones, and each tends to form in a specific breed or species under specific conditions. Stones in the urinary tract are common in dogs and cats. Even though dogs and cats do get kidney stones, it is bladder stones that causes more problems. The medical terms for bladder stones are urolithiasis or cystic calculi.
Bladder Stones, Ureteral Stones, Kidney Stones, Cystotomy, Urolithiasis, Cystic Calculi
Urinary stones (urolithiasis) are a common condition responsible for lower urinary tract disease in dogs and cats. The formation of bladder stones (calculi) is associated with precipitation and crystal formation of a variety of minerals. Several factors are responsible for the formation of urinary stones. The understanding of these processes is important for the treatment and prevention of urinary stones. In general, conditions that contribute to stone formation include:
- a high concentration of salts in urine
- retention of these salts and crystals for a certain period of time in the urinary tract
- an optimal pH that favors salt crystallization
- a scaffold for crystal formation
- a decrease in the body’s natural inhibitors of crystal formation.
The sequence of events that triggers stone formation is not fully understood. High dietary intake of minerals and protein in association with highly concentrated urine may contribute to increased saturation of salts in the urine. Disease conditions such as bacterial infections in the urinary tract can also increase urine salt concentration.
The symptoms of bladder stones are very similar to the symptoms of an uncomplicated bladder infection or cystitis. The most common signs that a dog has bladder stones are hematuria (blood in the urine) and dysuria (straining to urinate). Hematuria occurs because the stones rub against the bladder wall, irritating and damaging the tissue and causing bleeding. Dysuria may result from inflammation and swelling of the bladder walls or the urethra, from muscle spasms, or due to a physical obstruction to urine flow caused by the presence of the stones. Veterinarians assume that the condition is painful, because people with bladder stones experience pain, and because many clients remark about how much better and more active their dog becomes following surgical removal of bladder stones.
Large stones may act almost like a valve or stopcock, causing an intermittent or partial obstruction at the neck of the bladder, the point where the bladder attaches to the urethra. Small stones may flow with the urine into the urethra where they can become lodged and cause an obstruction. If an obstruction occurs, the bladder cannot be emptied fully; if the obstruction is complete, the dog will be unable to urinate at all. If the obstruction is not relieved, the bladder may rupture. A complete obstruction is potentially life threatening and requires immediate emergency treatment.
In some selected referral centers, another option may be available to treat bladder stones. This option is ultrasonic dissolution, a technique in which high frequency ultrasound waves are used to disrupt or break the stones into tiny particles that can then be flushed out of the bladder. It has the advantage of immediate removal of the offending stones without the need for surgery. Your veterinarian will discuss this treatment option with you if it is available in your area.