Bladder Stones (Cystic Calculi)

Bladder stones (also known as cystic calculi) are a very common disorder of both dogs and cats. Bladder stones in the urinary bladder often mimic the signs of a urinary tract infection, and sometimes happen in conjunction with an infection. Dogs and cats with bladder stones may urinate more frequently, urinate in the house or in odd places, and might have blood in the urine, or have urine that smells odd or stronger than normal. Bladder stones cause pain and discomfort, and can lead to further bladder problems. On occasion, bladder stones can lodge in a pet’s urethra causing a urinary obstruction-a life threatening emergency. Bladder stones almost always require surgery, known as a cystotomy, in order to remove them.

There are many different types of stones. The most common types of urinary calculi in cats and dogs are struvite and calcium oxalate stones.

Struvite bladder stones form when there are recurrent or chronic urinary tract infections, and in urine that is concentrated and basic. They used to be the most common bladder stone found in cats. If a bladder stone is known to be struvite, it can sometimes be dissolved medically with either a special prescription diet or medication. However, we need to be sure we are dealing with a struvite stone, as the treatment to dissolve them can worsen other types of bladder stones. Further complicating the picture is that most bladder stones are made up of multiple layers, which are often made up of different types of compounds. It is for these reasons that medical therapy of bladder stones has fallen out of favor.

Calcium oxalate stones are becoming the most prevalent stone we diagnose in both dogs and cats. Calcium oxalate bladder stones form in urine that is concentrated and acidic, as well as in response to certain diets. Unfortunately, calcium oxalate bladder stones can’t be dissolved and often repeatedly recur if strict dietary and management changes are not adhered to very closely, and sometimes even if they are.

Other, less common, types of bladder stones include cystine and urate.Urate (uric acid) bladder stones occur most commonly in Dalmatians because of a genetic defect in the ability to metabolize uric acid. Urate bladder stones in non-Dalmatians are usually a result of an underlying birth defect known as a liver shunt.

Pets that have, or previously had, bladder stones need to be monitored closely throughout their lives for recurrence.