Urinary tract stones occur in many species, including people. Whereas we tend to have stones form in our kidneys, in dogs and cats stones most commonly form in the bladder (although they can have kidney stones as well). The stones are formed of minerals, such as calcium and magnesium, that are usually dissolved in the urine. In dogs, the most common cause of bladder stones is a urinary tract infection. Certain types of bacteria can cause the pH of the urine to increase, which causes the minerals in the urine to start to form crystals. If these crystals stick together, they can form a stone. Some breeds of dogs, especially Schnauzers and Dalmatians, can form stones as a result of congenital problems with their liver or kidneys that causes them to lose extra minerals in their urine.

The most common symptoms of bladder stones are frequent urination, straining to urinate, and blood in the urine. Large stones, like the one this dog has, can be felt when the abdomen is palpated. When there are numerous small stones in the bladder, the bladder will feel kind of like a bean bag because the stones rub together. Many bladder stones are very obvious on X-rays, but some can only be seen with an ultrasound.

Occasionally bladder stones can cause a life-threatening obstruction of the bladder by becoming lodged in the urethra. If this is not caught and treated in time, the bladder can rupture. This is most commonly a problem in male dogs and cats because of their long, slim urethra, but it can occasionally happen in females as well.

There are several treatment options for bladder stones. Certain types of stones can be dissolved by putting the pet on a special diet. This can take several months, and it would not be practical for a stone as large as this dog's because of the length of time involved. The other option for treatment is surgery to remove the stone(s). For large stones, or ones that cannot be dissolved with a special diet, this is the best treatment. It may also be recommended even for smaller stones to avoid the risk of urethral obstruction. Once removed, the stones are sent to a lab to be analyzed to see what types of minerals they contain. Certain types of stones can reoccur, and a change in diet and sometimes medications can be used to help prevent recurrence.