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Ask a Vet: Can a special diet help my cat avoid urinary problems?

Q: I plan to adopt a couple of kittens/young cats in a few months. I want them on a diet that is least likely to cause urinary crystal formation because my current cats are suffering. What can I do to prevent issues?

A: On their own, crystals — which can be seen only under a microscope — are not always cause for concern. However, in some cats, they can aggregate into stones or jellylike plugs that block the flow of urine, a deadly situation. To prevent these problems, hydration is key — you’re doing all the right things! You can also lower the risk of urinary problems by reducing stress, ensuring access to clean litter and managing obesity. Special diets for urinary health are best reserved for cats with known problems.

What causes urination problems in cats?

Cats have urination problems like house-soiling and straining in the litter box because of behavioral problems or a variety of diseases of the urinary tract itself. Before you spend a lot of money on treatment and prevention, it’s important to first understand what’s behind your cat’s problem.

• Behavioral problems. If you have a male cat that deliberately pees on walls or other vertical surfaces, it’s more likely to be a behavioral problem. Behavioral problems are often triggered by stress over the presence of dogs or an inadequate litter box setup. Special diets and medications for diseases of the urinary tract won’t do anything for behavioral problems; they might even create more stress for your cat and cause issues like diarrhea.

• Urinary tract diseases. Straining to pee without producing a good stream (sometimes while vocalizing), peeing tiny amounts more often than normal, or having blood in the pee are all signs that your cat may have a urinary tract disease. These include kidney or bladder stones, bladder inflammation (cystitis), urinary tract infections, bladder cancer and even foreign material (I once treated a cat that couldn’t pee because of obstruction by a BB pellet). One of the most common urinary diseases in cats is cystitis, with or without blood clots, stones or jellylike plugs that can block the flow of urine. Cystitis tends to occur in young adult, male, overweight and indoor-only cats; it can also be exacerbated by stress. Unlike in dogs, young adult cats with cystitis rarely have urinary tract infections, so antibiotics don’t help.

What’s all the fuss about crystals?

When cats don’t consume a lot of water, their urine becomes concentrated and supersaturated with certain substances, most commonly struvite and calcium oxalate. These substances can then form crystals (similar to making crystals from rock candy). Initially, the crystals themselves can be seen only under a microscope, and they aren’t painful — so crystals alone aren’t a sign of disease. But if the process continues, crystals can be building blocks for the formation of stones and plugs.

Plugs, basically a cat thing, begin when crystals, tissue debris and blood form a sludge in the bladder. When a cat tries to pee, this sludge forms a plug that can block the urethra (the tube that connects the bladder to the outside world). Think of a plug like partially set Jell-O with tiny pieces of fruit (the crystals and debris) in it. Plugs are most likely to be a problem in male cats because of the shape and narrow diameter of the male urethra.

Why are stones and plugs bad?

Like a plug, stones that form in the bladder can block the urethra. Cats with stones or plugs in their urethra strain in the litter box, and their bladder becomes distended with urine — a life-threatening condition. If your cat is straining to pee and no urine is coming out, take them to an emergency clinic immediately. A delay of just a few hours here can be the difference between life and death.

Stones that form in the kidneys are more insidious. If these pass, they can easily block one of the ureters (tubes connecting each kidney to the bladder), because a cat’s ureter is only twice the diameter of a human hair. Fluid backpressure from the obstruction can cause permanent kidney damage. But because cats need only one normal kidney — and because cats are good at hiding signs of pain — if the other kidney is healthy, you could be completely oblivious to such a serious event.

Conversely, if the other kidney is diseased (usually because of a previous stone), obstruction of the ureter results in obvious illness, like not eating and vomiting — because now both kidneys are not working. Some of these cats can be helped with medical therapy (intravenous fluids and medications), but most need urinary bypass surgery. This surgery is risky and best performed by a board-certified veterinary surgeon that has plenty of experience with the procedure. The cost for surgery with ongoing care often exceeds $10,000. We see this often in our hospital, and I really wish we could prevent it.

Can diets prevent these problems?

The “ideal” diet for cat urinary health should prevent stones and plugs — not necessarily crystals — because stones and plugs irritate the urinary tract and obstruct urine flow.

Because stones and plugs that block the urethra often contain struvite, many nonprescription diets marketed for feline “urinary health” are designed to reduce urine pH, magnesium and phosphorus levels — conditions that predispose to struvite disorders.

But it’s not that simple. More than 90% of kidney stones contain calcium oxalate, and in some cats, diets that prevent struvite stones and plugs can predispose them to kidney stones — which might be worse.

Because the wrong diet can have unintended consequences, special diets are best prescribed for cats with a known problem. Regardless of the problem, hydration is a key component of any management plan, says Jodi Westropp, a professor at the University of California at Davis with a special interest in feline lower urinary tract diseases.

Ultimately, the best way to prevent urinary problems from happening in the first place is to promote water intake and minimize conditions that predispose cats to cystitis, such as obesity and a sedentary indoor lifestyle. Because cats with an outdoor lifestyle can harm wildlife and are prone to other diseases, consider a “catio” (enclosed outdoor patio for cats — try a catio tour). And you can encourage your cat to drink more water by feeding it a canned diet, providing a drinking fountain, replacing water daily and placing different types of water bowls around the house in low foot-traffic areas. (Although my cat Freckles likes to drink out of the dog’s water bowl, perhaps to taunt him!)

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