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Cat walking in little box

The essentials

  • Certain risk factors can increase your cat’s chance of developing urinary crystals — Middle-aged, overweight male cats that drink too little water are most at risk of urinary crystals. 
  • Cats typically develop two crystal types —The most common types of crystals you’ll find in your cat’s urine are struvite crystals and calcium oxalate crystals.
  • Not all urinary crystals are dangerous to your cat — While some urinary crystals can lead to stone formation, others are a completely normal finding in your cat’s urine.
  • A good diet is an essential part of urinary crystal management — A proper feline diet ensures your cat’s urine remains at the correct pH level and, along with adequate hydration, can go a long way toward preventing crystal development.

What are urinary crystals in cats?

Although it may sound exciting to have a cat that’s producing crystals, these shiny objects are not something you want for your feline friend. Urinary crystals are microscopic structures that can form in the urine of a healthy, normal cat. They can also develop as a sign of an underlying medical problem. A cat’s bladder may contain large amounts of crystals that can congregate to form stones, also known as uroliths.

What’s the difference between urinary crystals and stones in cats?

Urinary crystals and urinary stones are terms that are often used interchangeably, but they are different. A few crystals in your cat’s urine likely won’t cause a problem, but even one stone can lead to surgery.

Bladder stones form due to a buildup of crystals in a cat’s bladder. The presence of urinary crystals increases mucus production. Together, the crystals and mucus ball up to form mucus plugs or bladder stones. Stones can form in as little as a few weeks or take months to develop.

What types of urinary crystals develop in cats?

There are two types of urinary crystals that typically develop in cats: struvite and calcium oxalate.

Struvite crystals. Struvite crystals have a characteristic “coffin box” shape when examined under a microscope. Typically, struvite crystals develop in alkaline urine, which is urine that has a high pH. They generally develop without a urinary tract infection, making them sterile uroliths. Struvite uroliths that are due to a UTI are rare but tend to occur in kittens and older cats. Struvite crystals can also be present in the urine of healthy cats.

Cats between 2 and 10 years old have the greatest risk of struvite urolith formation. Struvites are common in the bladder but rare in the kidneys. Therapeutic diets that reduce urinary phosphorus, magnesium, and pH are very effective at dissolving and preventing struvites in cats.

Calcium oxalate crystals. Calcium oxalate crystals develop in urine that’s too acidic. In general, these crystals look like a square with an “X” through the middle when viewed under a microscope. Since struvite crystals develop so commonly in cats, most cat foods incorporate magnesium into their formulas, helping to make cats’ urine more acidic. This change has now led to an increase in the number of cats with calcium oxalate crystals. Burmese, Himalayan, Tonkinese, Devon Rex, Persian, and Siamese cats appear to be genetically predisposed to developing calcium oxalate stones.

Unlike struvite stones, calcium oxalate stones can’t be dissolved with special diets, and more aggressive treatment is often needed. In many cases, flushing the bladder with sterile fluids is not enough, so surgical removal is required. Another difference between the two crystal types is that calcium oxalate crystals are rarely seen in the urine of cats with a calcium oxalate stone. However, cats with a struvite stone will typically have struvite crystals present in their urine.

What causes urinary crystals in cats?

While the cause of urinary crystal development or crystalluria isn’t always known, it tends to occur frequently in domestic cats. What we do know is that some minerals are naturally found in your cat’s body. When these minerals are not properly processed by the cat’s urinary system, they can crystallize.

Certain risk factors predispose house cats to the development of urinary crystals. A few of the most common include:

  • Age. In general, middle-aged and senior cats are most likely to develop crystalluria.
  • Gender. Male cats are most at risk.
  • Weight. Urinary crystals tend to form most often in overweight or obese cats.
  • Breed. Certain breeds, like Tonkinese, Burmese, Devon Rex, Himalayan, Persian, and Siamese cats, are most at risk for developing calcium oxalate crystals.
  • Urine pH. Alkaline urine can cause struvite crystals to form, whereas acidic urine can lead to the formation of calcium oxalate crystals.

Additional factors that can predispose a cat to the development of urinary crystals include:

While cats can develop urinary crystals because of certain risk factors, crystals can be a normal finding on intermittent occasions. Also, urinary crystals can be present due to sample handling. If a cat repeatedly has a large number of crystals in a freshly collected urine sample and improper sample handling has been ruled out, then treatment for crystalluria is recommended.

Signs of urinary tract disease in cats

If your cat experiences any of the following signs, you’ll need to visit your vet ASAP:

Blood in the urine. A mass in the bladder, bladder stones, urinary tract infection, or interstitial cystitis can cause blood in the urine. The urine can be pink-tinged or even look like straight blood in severe cases.

Straining to urinate. As the bladder walls and urethra become inflamed and swollen, it becomes more difficult for cats to urinate. Straining to urinate can appear similar to constipation in cats, so watch carefully to determine which is the true issue.

Frequent urination. Cats with an inflamed bladder feel like they have to go all the time, so they’ll be in their litter box to urinate frequently.

Urinating outside the litter box. Urinating is painful when the bladder is inflamed. Some cats associate this pain with their litter box and then opt to use the bathroom in a new location.

Small amounts of urine. If your cat is urinating frequently, they won’t have time to build up a full bladder. Just a few drops may be eliminated during each trip to the litter box.

Excessive drinking. If your cat is urinating more frequently, they’re likely drinking more as well.

Yowling while urinating. Urinary tract inflammation hurts, and some cats will let you know how uncomfortable they are. You may hear yowling or meowing if your cat is in distress while they urinate.

Overgrooming. Many cats groom themselves in an attempt to soothe away the pain. You may notice fur missing around the genital region or on the sides of your cat’s abdomen.

Inability to urinate. In some cases, a mucus plug or bladder stones can block the urethra, preventing your cat from urinating. If your cat can’t urinate at all, they need emergency veterinary care to save their life.

🚨 If you notice your cat straining to urinate, get them to a vet immediately. They could have developed a urinary blockage, which is a life-threatening medical emergency.

The danger of urinary crystals in cats

Crystals themselves aren’t dangerous and can actually be a normal finding in some cats’ urine. It’s when crystals turn into stones or a mucus plug that they become a problem. These stones irritate the urinary tract and have the potential to cause a life-threatening urinary obstruction, especially in male cats.

Diagnosing feline urinary crystals

If the crystals aren’t causing a problem for your cat, they may go unnoticed. However, if you notice any of the above signs of a urinary issue in your feline friend, get them to your vet for a diagnosis. Urinary problems can quickly develop into a life-threatening emergency, so don’t wait around to see if the issue will improve on its own.

Your pet’s vet will likely perform a number of diagnostic tests to verify if your cat has urinary tract disease. Tests may include:

  • Urinalysis. Your cat’s urine sample can reveal information about pH, crystal content, and even whether or not your cat has an infection.
  • Urine culture. A urine culture will indicate whether your cat has a urinary tract infection caused by bacteria.
  • Blood work. Blood tests will check kidney function and electrolyte levels. Occasionally, bacteria from the bladder can travel up to the kidneys and cause a kidney infection, so checking kidney function through blood work is important.
  • Advanced imaging. To see if your cat has a stone or bladder mass — and to determine its location — your vet will likely recommend X-rays or an ultrasound.

👉 Some bladder stones won’t show up on X-rays, so your vet may recommend an ultrasound as well. An abdominal ultrasound can detect uroliths of all sizes and compositions, as well as bladder masses.

Cat getting an ultrasound

Shown here, a cat gets an abdominal ultrasound, one method for diagnosing bladder stones.

How urinary crystals are treated in cats

Treatment of your cat’s urinary crystals depends on the type. Struvite crystals or stones can be dissolved with a prescription diet, which can be accomplished in as little as two weeks. Calcium oxalate crystals and stones can be flushed out of the bladder if they’re small enough. Otherwise, large calcium oxalate stones must be surgically removed.

How to prevent urinary crystals from forming

If your cat requires treatment for urinary crystals or bladder stones, preventive measures are needed to keep new ones from forming. These cats will continue to develop urinary crystals and/or bladder stones if proper prevention isn’t implemented.

Keep your cat crystal-free with the following prevention guidelines:

Ask about a special prescription diet — Ask your vet about foods with lower phosphorus and magnesium concentrations. One option is Royal Canin’s Urinary SO cat food, which is proven to prevent both types of crystals from developing.

Offer your cat wet food — Dry food in the form of a prescription urinary diet is beneficial, but wet food also helps. The increased moisture content is great for urinary health.

Make sure your cat drinks sufficient water — The more water your cat drinks, the more likely they are to flush out excess minerals before they turn into crystals. Encourage your cat to drink more water with a cat water fountain.

Increase your cat’s activity level — Active cats are less likely to be overweight and develop urinary crystals. Figure out your cat’s favorite activities and spend time each day encouraging your pet to get up and move.

Schedule regular urinary checkups — Monitor your cat’s urinary health with regular checks of their urine to make sure new crystals haven’t formed.

Frequently asked questions

How do I treat crystals in my cat’s urine?

Treatment depends on whether the crystals are causing mucus plugs or bladder stones to form. Many cats can have crystals in their urine that are normal and require no treatment. Otherwise, struvite crystals can be dissolved through a prescription diet, but calcium oxalate crystals may form a stone. If a calcium oxalate stone develops, surgery is required to remove it.

Will crystals in my cat’s urine go away?

Crystals can be normal in a cat’s urine and often do not need to be treated.

What can I give my cat for urinary crystals?

If you’re concerned about the crystals in your cat’s urine, try a water fountain to encourage your cat to drink more water, which can help flush out urinary crystals. You can also give your cat a prescription urinary food to help break down struvite crystals.

Can cat food cause crystals to form in my cat’s urine?

Yes, some cat foods can unbalance urine pH, causing crystals to develop. Look for a cat food that is proven to support urinary health and prevent struvite and calcium oxalate crystals from forming. However, a more important cause is a lack of adequate water intake. Encourage your cat to drink as much as possible by giving them a water fountain and canned food.

Why do some cats get crystals in their bladders?

Many factors can increase a cat’s risk of developing urinary crystals. Overweight, middle-aged male cats that don’t drink much water are at an increased risk for urinary crystals. However, even healthy cats can have crystals in their urine periodically.