6 Common Types of Urinary Crystals in Dogs and Cats

Posted by Stacey Venzel
pug peeing

Learn what certain urinary crystals mean for your dog or cat.

One of the most common reasons for urinary complications in the veterinary world are urinary crystals. But it's not just important to note that crystals are present. Microscopic analysis determines which crystals are in the urine, and that can alter the plan of action for treatment and prevention.

Some common causes of crystals include improper diet, toxicity, dehydration, and underlying disease. Treatment might include antibiotics, fluid therapy, medication, or more aggressive means such as urinary catheters or surgery.


The most common urinary crystal, struvites look like rectangular glass prisms under the microscope. Bacterial infections in the urinary tract can accumulate enough to cause struvite crystals. An overload of struvites commonly results in bladder stones.

struvite crystals
Joel Mills/Wikipedia


Microscopic findings with no definitive shape but clearly harboring traits akin to crystals are classified as amorphous. These are typically comprised of either urates or phosphates.

Calcium Oxalate

These crystals can be classified as either monohydrate or dihydrate. They typically resemble a box with an X in the center. Others can resemble clear little seeds as well as picket fences under the lens. Elevated levels of calcium or antifreeze toxicity can cause these crystals.



These crystals appear as clumps of sharp fuzz under magnification. Bilirubin is important in the breakdown of waste products in the body's blood. It is found in both bile and urine, adding to their yellow hue.

Disorders that note yellowing of the skin--such as bruising and jaundice--are the result of bilirubin build-up, sometimes in natural healing levels and other times in concerning amounts. Excess levels can be indicative of a liver disease.


A hexagonal shape distinguishes these crystals from others. They are indicative of renal complications that eventually leads to stones.

Ammonium Biurate

These crystals appear as thorny apples through the microscope. They typically indicate stones are present.

If your dog or cat is showing changes in frequency of amounts of urination or drinking, or incontinence, it is best to take him or her to a veterinarian. Male cats straining to urinate should be taken to the vet immediately as this is an emergency situation.

Veterinary medicine has a number of tactics for tackling urinary crystals, so be sure to speak to your veterinarian about treatment options. Note that some breeds are more predisposed to certain crystals than others.

Have you heard of other urinary crystals in dogs and cats? Share your thoughts in the comments below.

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6 Common Types of Urinary Crystals in Dogs and Cats