Why do cats get crystals in their urine?

Estimated Reading Time 5 minutes
Why do cats get crystals in their urine?

Crystals in the urine are medically referred to as ‘crystalluria’. This occurs in cats when the urine is highly concentrated. Crystalluria is not always a sign of urinary tract infection or kidney stone formation. Continue reading to learn about the causes, symptoms, and treatment of urine crystals in cats.

Are you concerned about your pet?

Book a video consultation with an experienced veterinarian within minutes.

  • Professional vet advice online
  • Low-cost video vet consultations
  • Open 24 hours a day, 365 days a year

Causes of Urine Crystal Formation in Cats

The formation of crystals in urine occurs when there is supersaturation or a high concentration of crystal-forming minerals that naturally occur in urine. These minerals can clump together and form crystals. Other factors that can predispose to the formation of crystals in cats include:

  • Abnormally concentrated urine
  • Urine with unusually high or low pH
  • Diet
  • Consumption of certain toxins

In some cases, crystals in the urine may be artifacts of handling. It could be that the urine sample was refrigerated before analysis or left at room temperature, which would result in the precipitation of substances in the urine that would have remained otherwise dissolved and form crystals. When there is crystalluria after the urine temperature has begun to cool, it should not be considered medically significant.

When crystals are present in the urine, your vet needs to establish whether crystalluria is medically significant so a treatment regimen can be formulated if necessary.

There are several types of urine crystals, thus when your cat has them, your vet needs to determine what type is present so an appropriate medical approach can be made. Certain types of urine crystals can also be an indication of an underlying medical problem that should also be identified. Unless the underlying cause is addressed, urine crystals will be a recurrent problem.

Types of Urine Crystals

Urinary crystals are classified based on their mineral composition. There are struvite, calcium oxalate, and urate crystals. These are just some of the most common types of crystals that can develop in cats.

Certain conditions can help create a favorable environment for the development of crystalluria. It could be a problem caused by the presence of minerals or other chemicals in the urine. The existing urinary tract environment may also be an important contributing factor to crystal formation. Certain issues that affect these conditions include:

Why Cats Develop Urinary Crystals and Stones

The urine of cats is highly concentrated and acidic, which predisposes them to urinary crystals, and even stone formation. The presence of certain minerals or the abundance or deficiency of other substances in the urine can multiply the risks for cats. Other factors such as the cat’s diet, urine pH, and inflammation or infection are important contributing factors.

Although it's unclear what initiates stone formation, many experts think that an excess of stone-forming minerals in the urine form crystals that clump together to form a stone. With time, the stone gradually increases in size. The rate at which this happens will depend on the factors and conditions present; some stones can take weeks or even months to grow big and cause a problem. Some stones can get lodged in any part of the urinary tract, most commonly in the urethra, and block the passageway of urine.

In cats, stones that develop in the upper urinary tract are mostly calcium oxalate. A higher percentage of calcium oxalate is also found in the lower urinary tract. In cats. the presence of calcium oxalate stones is associated with hyperparathyroidism, idiopathic hypercalcemia, and other disease conditions that cause increased excretion of calcium in the urine. Struvite stones, also known as magnesium ammonium phosphate, are also very common in cats.

Symptoms of Urinary Crystals and Stones in Cats

Cats with very tiny urinary stones don’t usually exhibit any symptoms. However, the presence of larger stones in the lower urinary tract can cause obstruction and irritation of the urethral lining. These can interfere with urination. When these problems are present, affected cats may have the following symptoms:

Kidney stones in cats are rare and don’t usually cause any symptoms, except when their presence in the kidneys triggers inflammation, or they pass into the ureter. A stone lodged in the ureter can lead to vomiting and depression. There could also be pain in and around the cat’s kidneys.

Unfortunately, it’s difficult to detect that your cat is in pain. Cats are wired to hide any signs of pain and discomfort, a trait that they have inherited from their wild ancestors. In the wild, displaying pain shows vulnerability which can make them prime targets of predators.

How Urinary Crystals and Stones are Detected

In some cases, the stones are big enough that veterinarians can detect them by pressing the cat’s abdomen. Urethral stones may also be detected when a vet performs a rectal exam or when there is an attempt to insert a catheter. When a stone is detected and its location is known, the entire urinary tract is examined to determine if there are more stones present.

Stones as small as 3 mm in size can be detected with x-rays and ultrasound tests. A urinalysis and urine culture can also help diagnose the presence of stones and urine crystals.

Prevention & Treatment of Urinary Crystals in Cats

The treatment of urinary crystals and stones and prevention of recurrence will depend on their type and location. The following measures are usually a part of the treatment and prevention of stones:

  • Surgical removal
  • Special diet
  • Lithotripsy - a special procedure that harnesses sound waves to break down stones
  • Medication

When a stone is removed, laboratory analysis can help identify the type of mineral composition. This important information can help your vet prescribe the medication that can prevent more stones from forming. Close monitoring of cats that are undergoing treatment for crystals or stones should be made. They will have to be brought back to the vet at specific times for additional testing.

If a urinary tract infection is present, a round of antibiotics is usually prescribed to eliminate the problem. Other important recommendations will include avoiding certain mineral and vitamin supplements and encouraging adequate water consumption.

Read more:

The Cat-Lover’s Guide to Litter Box Bliss

Safety Considerations for Indoor and Outdoor Cats

How to Choose the Right Food for Your Cat

Need to speak with a veterinarian regarding your cat’s urinary problem or another condition?

Click here to schedule a video consult to speak to one of our vets. You can also download the FirstVet app from the Apple App Store and Google Play Stores.

Are you concerned about your pet?

Book a video consultation with an experienced veterinarian within minutes.

Get started
  • Low-cost video vet consultations, 24 hours a day Low-cost video vet consultations, 24 hours a day
  • Experienced, licensed vets Experienced, licensed vets
  • Over 700,000 satisfied pet owners Over 700,000 satisfied pet owners
Low cost consultations, 24 hours a day.Low cost consultations, 24 hours a day.

With FirstVet, the vet clinic and pet shop are only one tap away. Get fast advice, trusted care and the right pet supplies – every day, all year round.


FirstVet Inc

900 3rd Ave 29th Floor


New York