Like humans, dogs can develop a variety of bladder stones. These stones are rock-like structures that are formed by minerals. Some stones form in alkaline urine, while others form when the urine is more acidic. Bladder stones are very common in dogs, especially small breed dogs.
The most common signs that a dog or cat has bladder stones are blood in the urine and effort to urinate. Blood is seen through the bouncing stones that hit the bladder wall. This can irritate and damage tissues and cause cystitis, which is inflammation of the bladder. The stress of urination occurs due to the inflammation and irritation of the walls of the bladder or urethra, or due to muscle spasms. The stone itself can even obstruct the flow of urine if it blocks the urethra. Small stones can get stuck in the urethra and cause complete obstruction. This can be life-threatening if the obstruction is not relieved as the bladder can burst as more urine is produced without it being able to continue.
Bladder stones form due to changes in urine pH. Normal dog urine is slightly acidic and contains waste products like dissolved minerals and enzymes like urease. Urease breaks down excess ammonia in the urine. An ammonia overload in the urine can cause a cystitis and thickening known as a cystitis. There are a variety of stones that can form in the bladder, some form in acidic urine while others form in alkaline urine. The two most common types of stone are struvite and oxalate. Struvite stones are formed when the pH of the urine rises and becomes alkaline. Calcium oxalate stones form when the pH of the urine drops, making the urine more acidic.
Bladder stones can be diagnosed on a physical exam if your veterinarian does an abdominal palpation. In some cases the bladder is too painful or the stones are too small to be felt. Bladder stones can then be found using diagnostics such as x-rays and ultrasound. Treatment for bladder stones depends on the type of stone found. There are several options including diet change, surgical removal, and nonsurgical removal. Diet changes can be made to adjust the pH of the urine, which can help dissolve stones and prevent new stones from forming. Antibiotic therapy is typically required while the stones are being broken up. Non-surgical removal involves inserting a catheter into the bladder and flushing out the stones. This is only effective for very small stones and typically requires sedation or general anesthesia. Surgical removal is indicated when there are large stones, a large number of stones, or when dietary treatment is unsuccessful.
Prevention of bladder stone formation begins with diagnosing your dog’s specific stone type and then includes treatment with a lifelong therapeutic diet. Frequent tests may be needed to determine your pet’s urine pH, as well as biannual x-rays or ultrasounds to detect early stone formation. If you have any concerns about your pet’s bladder health, speak to your veterinarian for control.
Dr. Shana Bohac is a veterinarian and owner of the Navarro Small Animal Clinic.