Bladder Stones


What are bladder stones?

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

Bladder stones, and their smaller relatives urinary crystals, are accumulations of minerals that generally form when chemicals dissolved in the urine precipitate out of solution. These initially form microscopic deposits, but over time they can grow to form crystals, and eventually larger stones. Bladder stones can become sizeable – it’s not uncommon to see stones as big as a golf ball and sometimes even larger.


What causes bladder stones?

Bladder stones are generally the result of 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 a number of different 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 chemicals are found in meat, and animals on an unbalanced, high meat and high protein diet are much more likely to develop stones. Diet also strongly influences urinary pH, another major factor in crystal and stone formation.

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


What are the common signs of bladder stones and crystals?

Many bladder stones cause little discomfort or irritation, at least initially, but over time they grow and 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 quite 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.


How are bladder stones diagnosed?

Your vet will perform a careful physical examination, but definitive diagnosis requires an x-ray and/or an ultrasound, as well as a urine test.


How are bladder stones treated?

Most bladder stones need to be surgically removed in an operation called a cystotomy. This 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. Great care must be taken as with any surgery, but the procedure is generally fairly straight-forward and complications are rare. The bladder stones that were removed would normally be sent for laboratory testing to determine the stone chemistry and how to prevent more stones forming in future.

In some cases, it may also be possible to avoid surgery, instead slowly dissolving the stone using a special diet. This does take a number of months, but in depending on the stone type it can be a gentle and effective treatment.

If your vet suspects that a stone is blocking the urethra and the animal cannot pass urine they will immediately pass a catheter to relieve the blockage and stablise the pet prior to any surgery.


Can bladder stones be prevented?

Definitely. Due to improvements in diet and care, bladder stones are much less common than they were even ten 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. Commercial or home made diets are both excellent choices, as long as they are well formulated and balanced. For a commerical diet, check for an AAFCO accreditation on the side of the packet. This certifies that the food has been formulated according to accepted veterinary guidelines. For home-made diets I’d suggest following a recipe from one of the online home-cooked diet websites.

If your dog or cat has been diagnosed with crystals or urinary stones they will need to be on a special diet, as they are highly prone to forming new stones in future if not treated. These diets are carefully balanced with low levels of the offending minerals. Due to the very specific formulation these stone prevention diets I’d recommend using a commercial prescription food. Your vet will be able to advise you on which specific diet is suitable for your pet based on their previous stone and urine test results.


All pets should also have free access to as much water as they would like.  Some vets recommend feeding a canned or wet diet as well to increase water uptake. You can also encourage your pets to drink more by installing a water fountain – these work really well with cats who often prefer to drink from running water. Remaining well hydrated will prevent over concentration of urine, which greatly reduces the chance of crystal formation.



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