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The essentials
- Certain risk factors can increase the chance of developing urinary crystals — Overweight, neutered male cats have the highest risk, especially if they don’t drink enough water.
- 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 diet and 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 cats, dogs, horses, pigs, and even humans. They can also develop in normal, healthy individuals or as a sign of an underlying medical problem.
A cat’s bladder containing large amounts of crystals can result in congregating to form stones, also known as uroliths. Some crystals are more likely to form stones than others. A few crystals aren’t usually cause for concern, but stone formation certainly is.
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Urinary crystals vs. urinary 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 concern, 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 but may take months to develop.
What types of urinary crystals develop in cats?
Many types of urinary crystals may be seen in cat urine but the most common to develop are 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 (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 (called “voiding urohydropropulsion”) 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 struvite stones will typically have struvite crystals present in their urine.
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Symptoms of urinary crystals 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 more often than usual.
- 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 tell you how uncomfortable they are. You may hear yowling or meowing if your cat is in distress while they urinate.
- Over-grooming. 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 life-saving emergency veterinary care. If the bladder becomes too full, it can rupture.
🚨 If you notice your cat straining to urinate, get them to a vet immediately. A urinary blockage is a life-threatening medical emergency.
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:
- Dehydration
- Infrequent urination
- Improper diet
- Toxin ingestion (e.g., antifreeze)
- Urinary tract infections
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 numerous crystals in a freshly collected urine sample and improper sample handling has been ruled out, then treatment for crystalluria is recommended.
The danger of urinary crystals in cats
Crystals themselves aren’t dangerous and can 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 difficulty 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 issues 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 several 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 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.
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 usually be dissolved with a prescription diet. Calcium oxalate crystals and stones can sometimes be flushed out of the bladder if they’re small enough. Otherwise, large calcium oxalate stones must be surgically removed. Some urinary crystals cause urinary tract infections in cats, as well. These are typically treated with antibiotics. However, your vet may require a urine culture to determine which antibiotics to use.
If your male cat has a urinary blockage more than once or twice, your vet may recommend a surgery called a perineal urethrostomy (more commonly called a PU). This intense surgical procedure involves the removal of the narrowest part of the urethra, creating a larger opening for the urethra to pass urine (and crystals). PU surgery is a very delicate procedure and should be performed by a specialist whenever possible. Aftercare is difficult for both the owner and the cat, so this decision must not be taken lightly.
Dr. Dwayne AlleyneSince this is a very complicated surgery, the best-case scenario is to have this surgery done by a specialist as the first option. If cost is a concern then there should be an understanding there is a higher risk of complications if surgery is not performed by a specialist.
👉 Read about one cat’s PU journey from pre-op preparation to post-op care.
Another cause of urinary blockage (again, particularly in male cats) is feline idiopathic cystitis (FIC). FIC, formerly called feline lower urinary tract disease (FLUTD), causes inflammation in the bladder and urinary tract that can lead to stricture (abnormal narrowing). If your cat doesn’t have crystalluria, this could be the problem, although many cats that have urinary blockages have both crystals and FIC.
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. Some options include Royal Canin’s Urinary SO cat food, Hill’s Science Diet c/d or s/d, and Purina Pro Plan Veterinary Diets UR.
- Offer your cat wet food. Dry food in the form of a prescription urinary diet is beneficial, but wet food also helps due to the increased moisture content.
- 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 by regularly checking their urine to make sure new crystals haven’t formed.
The bottom line on crystals in your cat’s urine
Crystalluria is not always a big problem for cats. However, if your cat displays any symptoms of urinary crystals or blockage (particularly important for males), get your cat to the vet right away. The best treatment for urinary crystals and blockages is prevention. Having your vet perform a urinalysis on your cat during their annual check-ups is a great way to recognize crystalluria before it becomes a major issue. If you’re worried about your cat’s urinary tract for any reason, go to the vet! You’d much rather go in for nothing than miss the signs and end up with expensive surgery or emergency vet bills.
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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. Some crystals are normal and require no treatment, while others can form stones necessitating surgery.
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, go to the vet straight away. You can implement a water fountain to encourage your cat to drink more water, which can help flush out urinary crystals. You can also give your cat 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 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.
How long do cats live with urinary crystals?
The answer largely depends on the severity of your cat’s crystalluria. If you have a male cat that blocks consistently due to crystals, has a PU surgery and still develops a urinary blockage, the best option for him may be euthanasia. If your cat does well on prescription food and doesn’t get blocked, they should be able to live throughout their normal lifespan.
