My dog has calcium oxalate bladder stones. What are they?
Bladder stones (uroliths or cystic calculi), are rock-like formations of minerals that form in the urinary bladder, and are more common than kidney stones in dogs. There may be a large, single stone or a collection of stones that range in size from sand-like grains to gravel.
One of the more common uroliths in the dog is composed of calcium oxalate crystals.
What causes calcium oxalate bladder stones to form?
The exact cause of calcium oxalate bladder stones is complex and poorly understood at this time. Normal dog urine is slightly acidic and contains waste products from metabolism including dissolved mineral salts and other compounds. These mineral salts will remain dissolved in the urine as long as the pH stays within a narrow range, and as long as the urine does not become too concentrated.
Current research indicates that urine high in calcium, citrates, or oxalates and is acidic predisposes a pet to developing calcium oxalate urinary crystals and stones. Recent studies have shown diets that cause high urine acidity (urine pH less than 6.5) may predispose dogs to develop this type of bladder stone.
There are likely other causes of calcium oxalate bladder stones. Over-usage of antibiotics may reduce numbers of the intestinal bacteria Oxalobacter formigenes whose sole nutrient is oxalate. In dogs with low populations of Oxalobacter, excess oxalate is secreted in the urine, increasing the likelihood that calcium oxalate crystals and stones can form if the urine is highly concentrated or becomes acidic.
What other kinds of stones are there?
Gall stones form in the gall bladder and contain bile salts. Kidney stones are mineralized formations that develop in the kidney. Neither of these are directly related to bladder stones. Even though the kidneys and urinary bladder are both part of the urinary system, the development of kidney stones is not usually linked to the development of bladder stones. All stones form as a result of disease or inflammation in the affected structure.