Bladder stones in dogs
Bladder stones, or urinary crystals, are a common problem in dogs. Urinary crystals are small “particles” that form in the urine. When these particles clump together, they eventually become bladder stones.
When your dog suddenly urinates indoors, repeatedly urinates only small amounts, and/or there is blood in the urine, you may suspect urinary crystals or bladder stones.
There are several types of bladder stones, or urinary crystals, that can form in a dog’s urinary tract. Types of bladder stones include struvite stones, calcium oxalate stones, urate stones, and cystine stones.
Struvite stones
These are the most common bladder stones in dogs and cats. In America, approximately 50% of animals suffering from bladder stones have struvite stones. Struvite stones can develop when a dog has a bacterial bladder infection or when the urine pH is alkaline (less acidic).
Treatment of struvite stones may consist of a special diet or surgical removal of the stones. A struvite diet makes the urine more acidic (lower pH), causing smaller struvite stones to dissolve naturally. A struvite diet is therefore a solution for smaller struvite stones when the risk of urinary tract blockage is low. A struvite-dissolving diet may be given to a dog for a maximum of 6 months.
When struvite stones are too large or there is a risk of the urinary tract becoming blocked, surgical removal of the struvite stones is necessary.
In some cases, struvite stones form as a result of a bladder infection. In this case, treatment consists of administering a course of antibiotics for the bladder infection.
*A diet to dissolve struvite stones is often lower in protein, magnesium, and phosphorus. A struvite-dissolving diet also contains urine-acidifying nutrients (ammonium chloride, methionine, phosphoric acid, sodium bisulfate, calcium chloride, or calcium sulfate).
Calcium oxalate
This type of bladder stone forms when a dog’s urine is highly concentrated or when the calcium level in the blood is elevated. Excess calcium in the blood may occur when a dog has hyperparathyroidism (an overactive parathyroid gland), hyperthyroidism (an overactive thyroid gland), kidney failure, or an excessive intake of vitamins A or D.
Treatment consists of surgically removing the stones. To help prevent calcium oxalate formation, it is important to encourage a dog to drink more, for example by adding water to dry food or feeding wet food. Any underlying health problem causing the elevated calcium level must also be treated.
Urate stones
Urate stones develop when the breakdown of uric acid is impaired. An elevated uric acid level can develop as follows: protein breakdown produces waste products that are normally further broken down by the liver. When the liver does not break down these waste products further, they enter the urine, resulting in an elevated uric acid level. The uric acid then combines with other substances in the urine to form so-called urate stones.
Treatment of urate stones consists of surgically removing the stones. Afterwards, a dog will need to drink more and therefore urinate more frequently, keeping the risk of the stones forming again as low as possible.
Two specific dog breeds are prone to developing urate stones: Dalmatians and English Bulldogs. In these animals, a genetic factor is often the cause of the increased uric acid level.
Cystine stones
Cystine is an amino acid released during protein digestion. The amino acid is present in small amounts in the blood. The kidneys filter cystine from the blood, after which it enters the “pre-urine.” The kidneys then reabsorb this amino acid, so only a small amount is excreted in the urine. However, in the presence of a genetic defect, the kidneys do not reabsorb cystine from the pre-urine. As a result, excess cystine is excreted in the urine. An elevated cystine level in the urine leads to the formation of cystine stones.
Treatment of cystine stones consists of surgically removing the stones. In addition, cystine diets are available that reduce the risk of cystine stones forming. These cystine diets have a low protein content, a moderate content of sulfur-containing amino acids, and urine-alkalizing properties. A cystine diet may be given for a maximum of one year.
