Kidney and Bladder Stones (Uroliths) in Dogs

Uroliths are commonly known as “stones” and can form anywhere in the urinary tract. Stones may be single or multiple; can vary in size; and come in a variety of compositions. Most stones form in the lower urinary tract; 97% of stones are found in the ureters, bladder, or urethra. There are more than ten different types of urinary stones that can form in the urinary system of dogs.

Uroliths are very common and can be an incidental finding that does not need intervention, depending on where the stone is located and whether it is impacting normal function of the urinary system. If a dog is not passing urine, urinating with a small stream, or straining to urinate, urgent veterinary attention is required. This may indicate a life threatening urinary obstruction.

Severe cases of uroliths may lead to a urinary blockage, which is life threatening.

Urinary obstruction leads to kidney failure in as little as two days. Affected dogs may deteriorate quickly.

The inability to pass urine can have severe systemic effects. Cardiac dysfunction and damage to the kidneys are two of the severe life threatening complications of a urinary blockage.

Male dogs are prone to having complications from uroliths due to their urethra being smaller in diameter, longer, and more curved than females which makes stones more difficult to pass. Small/toy breeds are more prone to forming uroliths compared to large and giant breed dogs.

Uroliths form due to sustained alterations in the composition of urine which lead to high concentrations of minerals. The overabundance of minerals and other substances initially form crystals which may join together into larger stones.

Factors thought to influence the formation of stones include acidity (pH) and concentration of the urine, nutrient imbalance in the diet, infection, and individual metabolic abnormalities.

Foreign objects, like sutures, and bacterial infections can also contribute to stone formation.

Diagnostics include:

• Blood work
• Urinalysis
• Abdominal imaging
• Electrocardiogram (ECG) if urinary blockage is suggested

Culture of the urine and any retrieved stones is typically performed as concurrent infection is common.

Treatment is determined by location of the stone, suspected type of stone, and if normal function of the urinary system is compromised. Most stones of the lower urinary tract need surgical removal. Most kidney stones are incidental findings and treatment is often not warranted.

Chemical analysis of stones identifies their mineral make up which can yield information on how better to prevent recurrence. Some types of stones can be dissolved with a specialized diet, but this method increases the risk of urinary blockage.

If secondary infections are present, they are treated with antibiotics.

Surgical removal of uroliths results in immediate correction of the problem. If a dissolution diet is attempted, the time to full dissolution is dependent on number, size, and type of stone. In general, dissolution diets take several weeks to months for full dissolution. Prognosis is very good for most types of uroliths with appropriate treatment but lifelong management is needed to prevent reformation.

Dietary management is the hallmark of prevention, although not all types of stones can be prevented with dietary management.

Prevention of uroliths involves investigation and treatment of any urinary infections, encouragement of water intake to dilute the urine, and a specialized diet that promotes balanced mineral intake. Preventive measures need to be continued for life or uroliths will likely reform.

Uroliths are not contagious.

Uroliths are common in dogs.

• Surgical removal
• Lithotripsy or extracorporeal shockwave therapy
• Treatment of concurrent infection
• Dietary dissolution
• Dietary management
• Increased water intake