Bladder stones in dogs
Bladder stones, or bladder sludge, are a common problem in dogs. Bladder sludge consists of small 'granules' that form in the urine. When these granules clump together, they eventually turn into bladder stones.
If your dog suddenly urinates indoors, urinates in small amounts frequently, and/or if there is blood in the urine, you might suspect bladder sludge or stones.
There are various types of bladder stones or sludge that can form in the urinary tract of dogs. Types of bladder stones include: struvite stones, calcium oxalate, urate stones, and cystine stones.
Struvite Stones
These are the most common bladder stones in dogs and cats; in America, about 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 can involve a special diet or surgical removal of the stones. A struvite diet acidifies the urine (lowers pH), causing smaller struvite stones to dissolve naturally. Therefore, a struvite diet is a solution for smaller struvite stones and when the risk of urinary tract blockage is low. A struvite dissolving diet should be given to a dog for a maximum of 6 months.
If struvite stones are too large or there is a risk of urinary tract obstruction, 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 involves administering a course of antibiotics against the bladder infection.
*A diet to dissolve struvite stones is often lower in protein, magnesium, and phosphorus. It 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 very concentrated or when the calcium level in the blood is elevated; too much calcium in the blood can occur when a dog suffers from hyperparathyroidism (overactive parathyroid gland), hyperthyroidism (overactive thyroid gland), kidney failure, or excessive intake of vitamin A or D.
Treatment consists of surgical removal of the stones. To prevent the formation of calcium oxalate stones, it is important to encourage a dog to drink more, for example by adding water to dry food or providing wet food. Treatment of any underlying health problem causing the elevated calcium level is also necessary.
Urate Stones
Urate stones develop when the breakdown of uric acid is reduced. An increased level of uric acid can arise as follows: during protein breakdown, waste products are formed that are normally further broken down by the liver. When the liver does not break down these waste products further, they end up in the urine, resulting in elevated uric acid levels. The uric acid then combines with other substances in the urine to form so-called urate stones.
Treatment of urate stones involves surgical removal of the stones. Afterwards, a dog will need to drink more, causing it to urinate more frequently, reducing the chance of stone formation.
Two specific dog breeds are prone to urate stones: the Dalmatian and English Bulldog. A genetic factor is often the cause of increased uric acid in these animals.
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, which then enters the 'pre-urine.' The kidneys normally reabsorb this amino acid, so only a small amount is excreted in the urine. However, due to a genetic defect, the kidneys do not reabsorb cystine from the pre-urine. As a result, an excess of cystine is excreted in the urine. This elevated cystine level in the urine leads to the formation of cystine stones.
Treatment of cystine stones involves surgical removal of the stones. Additionally, there are cystine diets that reduce the risk of cystine stone formation. These cystine diets have a low protein content, a moderate level of sulfur-containing amino acids, and urine-alkalizing properties. A cystine diet should be given for a maximum of one year.
