Bladder stones affect millions of dogs and cats every year. In many cases they can be asymptomatic, causing no outward signs or discomfort, but in others they can cause serious discomfort and even become life-threatening.

"Bladder stones and their smaller relatives, urinary crystals, are accumulations of minerals that form when chemicals dissolved in the urine precipitate out of solution," says veterinarian David Gething, of Creature Comforts www.creaturecomforts.com.hk. "These form microscopic deposits, but they can grow to form crystals, and eventually stones. Bladder stones can become sizeable and it's not uncommon to see stones as big as a golf ball."

Bladder stones result from a combination of factors, including a high-mineral and high-protein diet, abnormal urinary pH (acid or alkaline urine), and the dog or cat's underlying breed and genetics.

There are various types of crystals and stones, but the two most common are struvite and oxalate. Struvite crystals are composed of phosphorus, magnesium and urea, whereas oxalate crystals are composed of calcium and oxalate. "All of these are found in meat, and animals on an unbalanced, high-meat, high-protein diet are much more likely to develop stones," Gething says. "Diet also strongly influences urinary pH."

Chronic bacterial infections of the bladder predispose an animal to forming crystals and stones by altering the urine chemistry, acting as a microscopic seed on which the crystal can start growing.

Gething says that many bladder stones cause little discomfort, at least initially, but over time they grow, rub and cause irritation. This can result in blood in the urine, straining to urinate, and passing small amounts of urine frequently. It is also common for pets to urinate inside the house (or outside the litter box for cats) because they are distressed.

"In some cases, a small bladder stone or even a conglomeration of crystals can pass down from the bladder and become stuck in the urethra [the pipe connecting the bladder to the outside world]. This can block the flow of urine, a life-threatening emergency."

Signs of a urethral blockage include straining, but not producing any urine, often while making painful moans. If the urethral blockage is not cleared quickly toxins will build up in the body, resulting in weakness, lethargy and vomiting.

"A urethral blockage is a critical situation and the cat or dog must be seen by a veterinarian immediately," says Gething.

Treatment for most bladder stones involves a cystotomy. This operation involves carefully opening the bladder and removing the offending stones, then flushing out the pipes to make sure no crystals or small stone fragments remain. The removed bladder stones are tested to determine the stone chemistry and how to prevent more forming in future.

Gething says: "In some cases, it may also be possible to avoid surgery, instead, slowly dissolving the stone with a special diet. This does take months but, depending on the stone type, it can be a gentle and effective treatment."

Bladder stones can be prevented. "Due to improvements in diet and care, bladder stones are less common than they were 10 years ago. The most important step in preventing bladder stones is feeding a high-quality diet that is suitable for your pet's breed and age," the vet says.

Commercial or home-made diets are excellent choices, as long as they are well formulated and balanced. With a commercial diet, Gething advises checking for an AAFCO accreditation on the side of the packet. This certifies that the food has been formulated according to accepted veterinary guidelines.

If your dog or cat has been diagnosed with crystals or urinary stones, they would need to be on a special diet as they would be more prone to forming new stones if not treated. These diets are carefully balanced with low levels of the offending minerals. Your vet would be able to advise which diet is best based on previous stone and urine test results.

Gething says that all pets should also have free access to as much water as they like. Remaining well hydrated will prevent an overconcentration of urine and greatly reduce the chance of crystal formation.

"Stones and crystals used to be a major problem but with recent advances in diet, diagnosis and treatment these conditions are now very treatable and preventable. And a healthy balanced diet isn't just good for stones and crystals; it is one of the most important steps to maintaining overall longevity." 

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