Understanding Cat Bladder Stones (Uroliths)

Cat bladder stones, or uroliths, result from a build-up of crystals in the urine that form stones. Under the commonly-accepted Precipitation-Crystallization Theory, some cats' urine contains a level of compounds that is too high to dissolve in urine. Instead, the compound precipitates the formation of tiny crystals, which are bound together with mucus-like material to form bladder stones that increase in size and number over time. The high compound level may be due to diet or a prior feline bladder infection.

Increased Calcium Oxalate Stones

In the past, most cat bladder stones were made of a material called struvite. Food manufacturers then developed more acidic foods to counter the formation of struvite. While this helped, the higher acidity increased the amount of calcium in the urine, leading to the rise of calcium oxalate stones. Burmese and Himalayan cats appear genetically predisposed to developing calcium oxalate stones, which generally develop in cats between 5 and 14 years of age.

Symptoms of Bladder Stones

The presence of bladder stones results in a variety of symptoms, including: hematuria (blood in the urine); dysuria (difficulty urinating); urinating outside the box or in odd places; and genital licking. Because these symptoms are also consistent with feline bladder infections, an x-ray or ultrasound may be required to confirm the presence of stones. Some stones can be palpated by the veterinarian or are suspected because of pain on palpating the bladder. A urinalysis can help determine the type of stone.

Recurrent bladder infections, hematuria and dysuria are the main signs. Hematuria is caused by the stones irritating the bladder wall. Dysuria results when the stones block the passing of urine through the urinary tract. This causes abdominal pain that prompts the cat to cry out and stoop to urinate without success. Such obstructions must be treated promptly.

Treatment of Cat Bladder Stones

Treatment of bladder stones in cats is two-pronged: Eliminating the immediate problem and taking steps to ensure it does not recur. There are several ways to eliminate stones. If it is small and the cat is female, simply waiting for the cat to pass the stone may be appropriate. Male cats have narrower urinary tracts that make them more prone to stones.

Struvite stones may potentially be dissolved through dietary changes. Calcium oxalate stones that cannot be passed must be removed surgically through a cystotomy. Under anesthesia, the cat's abdomen is opened up, the stones removed, and the area stitched up. The cat is usually hospitalized for up to two days and given pain medication and antibiotics. Cultures are obtained to rule out infection.

Dietary changes are usually recommended for cats who develop bladder stones. Notably, 35% of cats with calcium oxalate stones also have elevated blood calcium; meanwhile, some cats have a vitamin B-6 deficiency, which can promote the development of stones. Such underlying conditions must be treated along with the stones. Then, the cat's diet can be adjusted to create a more dilute, pH-balanced urine, which will prevent the development of any one compound, following the Precipitation-Crystallization Theory. A high-fiber, low-protein diet, along with potassium citrate supplements, is recommended for stone prevention. Canned food is preferred over dry due to its high water content, which helps dilute the urine.