Bladder Stones – Why They Form and How to Prevent Them


Left – bladder stone visible on x-ray. Right – same bladder stone removed after surgery.

Bladder stones, also called urolithiasis, are a common occurrence in veterinary medicine. They come in all shapes and sizes and have several different factors that cause them. When formed, these stones irritate the bladder wall can can cause blood in the urine, straining to urinate, increased frequency of urinations, and possibly accidents in the house. They can occur at any age, and can happen to any breed of cat or dog. Bladder stones can be life threatening in the case of male dogs/cats, as the stone can become lodged in the urethra and cause a blockage.


So how do they form? Any substance found in the urine is a result of the kidneys. Your kidneys filter your blood and keep a stable balance of salts, minerals, and other substances in your body. Anything that is believed to be in excess in your bloodstream is excreted in the urine. It is believed that when a pet eats a diet too high in certain minerals, that these minerals are filtered by the kidneys and excreted in excess in the urine.


If the level of minerals is high enough, and other factors including pH and concentration of the urine is just right, then these minerals can form compounds called crystals. Crystals are microscopic and require a urinalysis to detect. When enough crystals are formed in the urine, they clump together and grow into a stone. There are several types of crystals, but the two most common we see are struvite (formed from magnesium, ammonium, and phosphorus) and calcium oxalate (formed from calcium). A bladder stone made from struvite crystals can be dissolved in the bladder with a special diet however, a stone made from calcium oxalate crystals cannot and must be surgically removed. Deciding which treatment option can be tricky however, as bladder stones can be made up of both types of crystals.

Crystals can also form due to bladder infections, liver/kidney disease, endocrine disorders, and certain types of cancers. Certain breeds are also more prone to developing crystals as well.


How to prevent them:

  • Feed your pet a well formulated diet that has been tested and reviewed by a veterinary nutritionist. Some of the patients we see that have bladder stones were being fed a homemade/raw diet. While their owners had the best intentions in feeding what they believed was right, many of these recipes available are not properly formulated. In other cases, we sometimes see patients that were on food from the pet store or even a diet purchased from a vet clinic. Those cases are often attributed to breed or genetic factors in developing stones which is why the next way of preventing bladder stones is equally important.
  • Bring your pet in for routine check ups! A veterinarian’s experience and knowledge can pick up on many things with an examination and thorough history. We often find problems on seemingly healthy pets with screening lab tests. Cats and dogs can be very good at hiding health issues as part of their survival instinct.