Crystals in Cat Urine: Signs, Causes, & Treatment

There are a variety of urinary issues that can be discovered in our feline family members. FLUTD, or feline lower urinary tract disease, is the broad term for the issues that occur in their urinary system, including the bladder, ureters, and urethra. One abnormality that is commonly found, but not often well understood is the presence of crystals in the urine, better known as crystalluria. What is this and is it always an issue that needs to be treated? Read on to learn more about how crystals in the urine can affect your kitty.

Causes Symptoms Diagnosis Types of crystals Treatment Prevention

What are crystals in cat urine?

Crystals are composed of minerals and other compounds present in urine. They are formed when a high concentration of these components glob together rather than remaining in their typical dissolved, separate state.

Causes of crystal formation in cat urine

The mere presence of these components, albeit in high concentrations, is not always enough to cause crystals to form. Some examples of other factors that can encourage or contribute to crystal formation in a supersaturated urinary environment include the following.

cat eating dry kibble from bowls

Diet

A diet that is not appropriately balanced may contain higher or lower than recommended amounts of essential minerals. Excess of these minerals that cannot be used by the body are excreted through the urine. Cats should be fed diets that meet the Association of American Feed Control Officials’ (AAFCO) set standards.

Some cats eat a strictly dry cat food diet. If they don’t drink enough water separately, they can become dehydrated. Lack of hydration can cause urine to be more concentrated, which can contain more of the building blocks for crystal formation.

Ingestion of toxins

The ability to cause crystal formation depends on the pathway through which the toxic substance is ingested. Here are two examples of toxicities that can result in urinary crystals.

Ethylene glycol, or antifreeze, is toxic to cat kidneys. It causes formation of calcium oxalate crystals within a few hours of ingestion.
Soluble oxalate-containing plants like shamrock plant, star fruit, curly dock, greasewood, lambsquarter, or rhubarb can be toxic if ingested in large quantities. This toxicosis can cause the formation of calcium oxalate crystals and rarely, acute kidney failure.

Abnormal urine concentration or pH

Urine concentration is measured to help determine how well the kidneys are functioning. This is most specifically in regard to water conservation versus water excretion. Excess water that is not needed by the body is excreted through the urine. Cat urine is typically concentrated, but an increase in concentration, or a super concentration, can be found in healthy cats that are not appropriately hydrated or in cats with some underlying disease process such as kidney disease, metabolic disease, or heart disease to name a few.

pH is the measurement of how acidic or alkaline (basic) a substance is. The ideal pH of urine is 6.3–6.6 in cats. Alteration of the pH can encourage the formation of urine crystals.

Bacteria

Some bacteria produce chemicals that can alter the pH of the urine. In changing the pH, the bacteria can contribute to creating an environment that encourages the formation of crystals.

Temperature changes

Changes in temperature can affect the formation of urine crystals. This is particularly important in urine sample handling.

Symptoms of crystals in cat urine

Crystalluria can progress into urinary stones or be present during an infection. So in monitoring for symptoms of crystals, one should be monitoring for anything abnormal in relation to urination. Listed below are a few examples of symptoms that can be appreciated in the event of any FLUTD that may include crystals:

Inappropriate urination (anywhere other than the litter box)
Blood in the urine
Straining to urinate
Increased or decreased urination
Increased vocalization while in the litter box
Excessive grooming of the urogenital area
Excessive drinking

Monitoring for symptoms specifically related to the presence of urinary crystals can prove frustrating for a few reasons. Crystals in the urine alone are not always problematic and therefore they are not always going to produce symptoms. That being said, one should always be on the lookout for changes in urination in their cat because while crystals may not be the specific cause of the symptoms, they can be contributing or worsening the issue if an issue does exist.

How do you diagnose crystalluria?

Ragdoll cat examined by vet

Testing

Urinary crystals are microscopic and cannot be appreciated with the naked eye. The best way to determine if your cat has urinary crystals is by taking them to the veterinarian and having diagnostics performed. The most important of these diagnostics is the urinalysis, or the analysis of a urine sample obtained from your kitty. Part of this test requires that some of the urine collected from your cat be spun in a centrifuge; some of that smaller sample is then placed on a glass microscope slide and reviewed on a microscope. During this review, urine crystals are not the only things that can be found: cells, casts, bacteria, yeast, sperm (in intact males), fat, and more can be observed and quantified.

Safekeeping

Sometimes, the presence of crystals in the urine can be an artifactual finding because of sample handling. Put simply, this means that sometimes the urine sample cannot be interpreted as soon as it’s collected. Most often, it is placed in a refrigerator for safekeeping: during this time, the components that were previously existing separately in that urine can come together to form crystals.

Urine collection

There are three ways to collect the urine that is needed to conduct this test, but in most veterinary settings, only two will typically be attempted in a cat that is not sedated or under general anesthesia.

Collection in the litter box

This is usually done by putting a special kind of cat litter in the litter box that won’t absorb urine, such as Nosorb, and collecting the urine from the litter box after your cat urinates like normal. This can be done at home and promptly brought into your vet clinic for interpretation. Try to call your veterinarian ahead of the urine collection: they may be willing to provide you with a syringe or tube to collect and store the sample for transportation. If you don’t feel comfortable collecting the sample yourself, your cat can be dropped off at the vet clinic for a few hours to see if they will urinate while in hospital.

Cystocentesis

This is performed with a sterile needle and syringe: the needle is inserted through the skin of the abdomen and into the bladder to collect a sterile urine sample. While it is best performed with ultrasonic guidance if this is available in your veterinary facility, it can be performed successfully without it. The temperament or attitude of the cat plays a big role in whether or not this procedure can be accomplished without sedation.

Placing a urinary catheter

This procedure is performed differently between males and females; and while it is routinely performed on male dogs with minor restraint, it is often much more difficult to do this in both male and female cats (and female dogs) without a sedative or even general anesthesia.

Types of crystals

Now that the presence of urinary crystals has been confirmed, it is important to specify the type of crystal. This helps to determine how to address the crystals or if they need to be treated at all. Urinary crystals are not “one size fits all.” The factors that play into the creation of urinary crystals also influence which type of crystal is formed. There are various types of urinary crystals that may be seen in cat urine such as:

Magnesium Ammonium Phosphate (Struvite)
Calcium Oxalate (Monohydrate vs Dihydrate)
Ammonium Urate(or Biurate)
Xanthine
Cystine
Bilirubin
Amorphous

The most common crystals formed in cats are calcium oxalate and struvite. It’s important to understand that while urinary crystals can be a symptom of a problem, crystals can also be seen in the urine of healthy cats and therefore may not cause notable issues.

Let’s discuss some of the attributes of these urinary crystals.

Magnesium ammonium phosphate

Struvite crystals, triple phosphate, or scientifically named, magnesium ammonium phosphate, are one of the most identified urinary crystals in both cats and dogs. The scientific name so eloquently lists the components that form this crystal and while they tend to form in alkaline urine, they can form in neutral urine as well. They are often clear and shaped like a coffin lid, a double-edged razor blade, or a prism.

While they can be found in cat urine without consequence, they can also bond together to create stones or bind with mucus to form urinary plugs. Both stones and plugs can cause blockages (mostly in male cats): they can get lodged in various parts of the urinary tract and prevent the flow of urine out of the body. This is a medical emergency that cannot wait to be addressed.

Struvite stones associated with a concurrent infection are more common in cats less than a year old and geriatric cats over 10, but the majority of feline struvite stones are sterile, or not associated with an infection.

Breeds predisposed to the formation of struvite crystals and stones include: Ragdolls, Shorthairs (Oriental and Domestic), and Himalayans.

Calcium Oxalate

Calcium oxalate dihydrate crystals are more common than their monohydrate counterparts. Calcium Oxalate Monohydrate comes in a variety of shapes including spindle, oval, and dumbbell. They are most notably associated with ethylene glycol toxicosis in cats and dogs.

Calcium oxalate dihydrate looks like a clear, square envelope with an “x” on it. While it is known that they do tend to form in a more acidic environment, there is still much to be learned about why these crystals form and advance into stones.

Older cats are the most predisposed to these crystals combining to form stones. Several feline breeds have been identified as predisposed. This list includes, but is not limited to: British, Foreign, and Exotic Shorthairs, Ragdolls, Himalayans, and Persians. A small amount of calcium oxalate crystals can be normal in some healthy cats, but this finding still needs to be interpreted in light of the cat’s overall clinical picture.

Ammonium biurate crystals

Ammonium biurate crystals are yellow to brown and spherical with irregular protrusions. These crystals, unlike struvite and calcium oxalate, are never considered normal in a healthy cat: they tend to be indicative of liver disease. While they can form in any pH environment, their preference tends to be a more acidic to neutral urine environment.

This type of crystal may form as a result of liver disease or vascular anomalies.

Xanthine

Xanthine crystals have been found in various shapes including spheroid, amorphous, or ovoid and are described as yellow to brown in color as well. They can be difficult to diagnose as they cannot be distinguished morphologically from ammonium urate.

Xanthine crystalluria is very uncommon in cats (and dogs) and is typically a result of a hereditary defect that causes a deficiency of the enzyme, xanthine oxidase. Xanthine is supposed to ultimately be broken down into uric acid: without that enzyme, xanthine is excreted into the urine where crystals and stones can form.

Cystine

Cystine crystals have been described as colorless, hexagonal plates that form in acidic urine. Cystinuria is the presence of cystine in the urine due to a hereditary condition. It is this presence that allows for the progression of cystine into cystine crystals and in more severe cases, cystine stones. Despite how uncommon it is, it has been reported in the following breeds: Domestic cats (short, medium, and long-haired), Maine Coons, Sphynxes, Siamese cats, and Korats.

Bilirubin

Bilirubin crystals are orange to reddish-brown, needle-like crystals that can occasionally be observed in the urine of healthy dogs, but they are always an abnormal finding in cats. They are usually an indicator of cholestatic disease, or an issue with the flow of bile from the liver.

Amorphous

Amorphous crystals are usually considered an incidental finding as they are small crystals for which the source cannot be identified. Some may represent fragmentation of larger crystals, but without evidence of other crystals, pH, or additional factors to try to determine their origin, they are deemed clinically insignificant.

Treatment for crystals in cat urine

Whether the crystals in the urine warrant treatment or not depends on the specific crystal in question, the amount of crystals appreciated in the urine testing, and risks associated with the presence of those crystals in your cat’s urine in light of their overall health. Let’s discuss some of the most common treatment options for urinary crystals.

Benign neglect: Just do nothing

More often than not, when crystals are found in the urine, the treatment of choice is no treatment at all. As mentioned before, the finding of crystals in the urine is often incidental and has no current medical significance.

This determination has to be made in light of your cat’s total clinical picture, but with the right diagnostics to confirm that there is no additional concern, doing nothing can absolutely be the appropriate course of action.

Prescription diet

The first step of medical therapy for many cases of crystalluria is changing your cat’s diet to one that can promote a healthier urinary environment. There are prescription diets to address the most common types of urinary crystals. For the less common crystals, you can work with your veterinarian to determine what diet is going to be most appropriate for your cat.

While prescription diets can be expensive, they are also a staple in urinary crystal management, prevention, and resolution depending on which crystal your cat is being treated for. These diets also come in both a wet and dry formulation, so you and your veterinary team can decide which options work best for your favorite feline.

Additional treatment

The presence of crystals in the urine without symptoms or other evidence of pathology typically is not going to require treatment beyond a diet change and some minor environmental changes like increasing access to water.

If there is evidence of infection, antibiotics may be prescribed as well.
If radiographs are performed and stones are found, additional treatments such as lithotripsy, a minimally invasive procedure to break down the stones, or surgical removal may be recommended.

Additional treatment modalities have to be determined in light of your cat’s physical exam and diagnostic results.

Prevention of crystals in cat urine

orange tabby cat in self-cleaning litter box

Preventing the formation of crystals in the urine has to be tailored to the type of crystals your cat has. In general, the following recommendations can help to facilitate a healthy urinary system:

Prioritize adequate hydration and exercise

Ensuring that your cat has access to fresh water is crucial in preventing urinary issues. Some kitties do not prefer standing water, so a water fountain may work really well for them. Either way, fresh water is the best water.

Active cats tend to use the bathroom more regularly. Making sure that your cat has access to stimulating toys and has an appropriate amount of quality play time with you or another family member daily is helpful.

Feed a high-quality, AAFCO-approved diet

Just because a food is advertised as high-quality or premium, doesn’t mean that it’s meeting all of your cat’s nutritional needs. A cat food diet, whether wet or dry, that has an AAFCO statement is most likely to meet all of your cat's nutritional needs. If your cat has other medical issues, talk with your veterinarian to determine the best diet for them.

Schedule regular vet visits

Vet visits are not just for when your cat is sick. Visiting the vet preventatively and with regular frequency is the best way to catch abnormalities early, like too many crystals in the urine.

Maintain a clean litter box

Having constant access to a clean litter box is encouraging to cats and prevents them from holding their urine unnecessarily.

Simplify your litter box maintenance with the Litter-Robot 4, the self-cleaning litter box that provides your cat with a fresh bed of litter after each use.

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