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If you share your life with a cat, you might know that litter box problems aren't uncommon. However, the particular affliction of bladder stones in cats doesn't receive the attention that it should. Read on to learn about the most common types of feline bladder stones — calcium oxalate and struvite — including how to prevent and treat them.
Basic Facts About Bladder Stones in Cats
Bladder stones, or uroliths, are simply organized accumulations of hardened minerals that are found in urine. They can occur anywhere along the urinary tract, from the kidneys all the way to the urethra — the narrow tube that carries urine from the bladder to the outside of the body.
Stones range in size. Your cat could have a tiny stone or one the size of their bladder. Stones also range in shape and color. They can be smooth or have jagged edges. Stones pose problems because they can damage the surrounding tissue, cause inflammation, scar tissue and predispose a cat to infection, especially if they have rough or jagged edges.
Crystals vs. Stones
If you've heard of urine crystals, you might be wondering how they differ from bladder stones. According to the Merck Veterinary Manual, when crystals clump together and grow, becoming visible to the naked eye, the result is called a stone. However, it should be noted that crystals may be present in certain urinary environments that favor the formation of a stone but is not a definitive precursor.
Clinical Signs of Bladder Stones in Cats
The signs that cats with bladder stones display differ depending on where the stones are located in the urinary tract. Many times, cats with bladder stones exhibit no signs at all. Other times, the stones may cause bladder irritation or infections, which may present as frequent trips to the litter box, frequent urination, blood in the urine, vocalizing while urinating, urinary accidents and decreased urination.
If a urinary stone becomes stuck, it may cause urinary obstruction also known as a blocked urethra so the cat cannot urinate at all. This is a life-threatening condition that requires prompt intervention. This is most often seen in male cats. If you notice your cat trying to urinate, but doing so unsuccessfully, you should see your veterinarian promptly. It's also important to consider that a cat with urinary obstruction may act like they're constipated. While the behavior may look similar, the results can be drastic — if you notice this behavior, it is likely a good idea to call your local vet to get their recommendation.
Types of Bladder Stones in Cats
The two most common types of bladder stones in cats are struvite stones and calcium oxalate stones. According to the American College of Veterinary Surgeons, while the development of these stones is complex, a cat's food may play a role. They also rarely form secondary to bladder infections in cats.
Radiographs and a microscopic exam of urine sediment may provide indications as to what type of stone your cat has. However, the identity of a stone cannot be determined unless it is collected and analyzed.
Calcium Oxalate Stones
Calcium oxalate stones are the most common urinary stone in cats, according to the Merck Veterinary Manual. They're most often seen in middle-aged to older cats. Breeds most likely to develop calcium oxalate stones include the Ragdoll, British shorthair, exotic shorthair, Himalayan, Persian and Scottish fold. Calcium oxalate stones can form in overly acidic urine. They may be seen in cats with elevated blood and urine calcium levels secondary to a condition called idiopathic hypercalcemia or in cats with chronic kidney disease.
This type of stone requires surgical removal. Infections and underlying conditions must also be treated. Once the stones have been removed, switching your cat to a therapeutic food formulated to reduce urine mineral content and increasing their water intake — by switching them to wet food, for example — may help prevent a recurrence. It's necessary to have your cat adhere to your veterinarian's recommended meal plan.
Struvite stones are typically found in younger cats who've been neutered. Unlike calcium oxalate stones, struvite stones in cats tend to form in highly concentrated alkaline urine. While any breed can be affected, those most at risk are the domestic shorthair, exotic shorthair, Ragdoll and Himalayan. Cats who consume high amounts of magnesium, phosphorus, calcium, chloride and fiber are also more likely to develop struvite stones.
A special therapeutic food, such as Hill's Prescription Diet, can help dissolve struvite stones. Therapeutic urinary foods come in a variety of flavors and forms and therapeutic treats may be available so your cat will not be deprived. In many cases struvite stones can be dissolved quickly. One study showed that stones were, on average, 50% smaller in just 2 weeks and the average time to completely dissolve stones in about a month. In most cases, it's recommended that a cat remain on a therapeutic food to prevent stones from returning. This is becase while a cat that may no longer be symptomatic of urinary issues, recurrence is possible if the cat resumes eating a food that contributed to stone formation in the first place. Keeping your cat on a pet food formulated for urinary health may help extend the time between urinary problems.
While bladder stones in cats have a high recurrence rate, they can be successfully treated. Together you and your veterinarian can determine the right therapy or combination of therapies to keep the stones at bay.
Dr. Laci Schaible
Dr. Laci Schaible is a small animal veterinarian in the pet technology space. She is the Head of Veterinary Medicine at Rhapsody.vet.