black and white domestic cat using litter tray

Urinary Crystals in Pets: Causes, Symptoms and Treatment


This article is written by Pet Circle veterinarian, Dr Carla Paszkowski BVSc and last updated by Dr Gillian Hill.

Has your pet been diagnosed with urinary crystals or urinary stones? Unlike humans, crystalluria (crystal formation in the urine) is very common in pets. Both cats and dogs can experience crystals in their urine, however we tend to see more issues in cats. In some cases, crystals can lead to a life-threatening obstruction in the urethra, restricting outflow from the bladder. (If you've ever heard someone refer to a 'blocked cat' - this is what they're referring to.

What are urinary crystals?
What causes urinary crystals?
What are the symptoms of urinary crystals?
What are the different types of urinary crystals?
How are urinary crystals diagnosed?
How are urinary crystals treated?
How can urinary crystals be prevented?

What are urinary crystals?

You might wonder how your pet even got these crystals; Did they drink a magic potion causing their insides to turn into a sparkly Swarovski-like cave of wonders?

Urine is a byproduct from blood filtration through the kidneys. It consists of around 95% water, with the remainder consisting of mainly salt, nitrogen, protein, minerals and toxins. Under certain conditions, these many different substances can solidify to become urinary crystals.

What causes urinary crystals?

There are many factors that affect the formation of crystals including chemical concentration, acidity or alkalinity of the urine, temperature, diet, infections, and other disease processes. Although the presence of some urinary crystals can cause problems or indicate an underlying disease process, certain crystals can also be found in normal urine from healthy animals.

cat using liter tray

What are the symptoms of urinary crystals?

Signs that may indicate the presence of urinary crystals include:

  • Urinating more frequently, often in smaller amounts
  • Straining to urinate
  • Frequent squatting
  • Urinating in inappropriate places
  • Blood in the urine
  • Pacing
  • Increased vocalization or calling out when urinating
  • Increased thirst
  • Reduced appetite
  • Lethargy

If crystals aren't treated, they can grow and bind together to create urinary stones, also known as bladder stones or uroliths. These stones cause a lot of irritation and can make it difficult for your pet to urinate. In some cases this stone can cause urinary blockage which is a medical emergency.

If your pet is displaying any of the symptoms listed above, or if you suspect they may have a urinary blockage it is essential to seek immediate veterinary attention. While urinary crystals do not always lead to stone formation, they are certainly a major risk factor.

What are the different types of urinary crystals?

The most common types of urinary crystals are listed below.

1. Struvite

Struvite crystals are a mineral consisting of ammonium, phosphate and magnesium. They are colourless prisms formed in neutral to alkaline urine and are often seen in normal urine, however they can also be linked with disease. Bacteria associated with urinary tract infections can increase ammonia concentration which is favourable for struvite formation. Many breeds are predisposed to these crystals including Miniature Schnauzer, Miniature Poodle, Cocker Spaniel, Bichon Frise, Lhasa Apso and Shih Tzu.

2. Calcium Oxalate

Calcium oxalate crystals are clear and shaped like square envelopes. They can be found in normal urine at any pH. Calcium oxalate stones are more common in male adult purebred dogs like Miniature Schnauzers, Yorkshire Terriers and Bichon Frises. Mature Himalayan and Burmese cats also have a hereditary predisposition. In addition calcium oxalate stones can be associated with diseases resulting in excess cortisol production (Cushings disease, medically known as hyperadrenocorticism) and elevated blood calcium (hypercalcaemia).

3. Cysteine

Cysteine crystals are made of a sulfur containining amino acid. They appear flat, colourless and are hexagonal shaped and form in acidic urine, often associated with a high protein diet. Cysteine crystals are more commonly seen in Newfoundlands, Dachshunds and English Bulldogs.

4. Ammonium Urate

Ammonium urate crystals are yellowish-brown in appearance and can be spherical or have thorn-like protrusions. They may occur in normal urine and are frequently seen in Dalmations and English Bulldogs.

How are urinary crystals diagnosed?

scientist looking through microscope

Your vet will likely have a strong suspicion of crystalluria based on your pet's symptoms. The first step towards diagnosis of urinary crystals involves a complete urinalysis. Your vet will be able to examine your pet's urine under a microscope and visually observe if crystals are present. A dipstik test will also be performed, as this will help your vet determine the acidity of the urine as well as the presence of any blood or infectious cells and bacteria. In some cases x-rays may be indicated, occasionally with special dyes. Ultrasound of the bladder and kidneys may also be required.

How are urinary crystals treated?

golden retriever at vet clinic with bandaged leg

Your vet will first treat for any emergency conditions, such as a bladder obstruction. If your pet has large stones, surgery may be required. If other conditions are present, such as cystitis or infection, your pet may receive antibiotics and pain relief.

Once these conditions are under control, you can focus on reducing the crystals in the urine. The course of action depends on the stone present. Some commonly occurring crystals, such as struvite, can be treated by feeding your pet a special prescription diet which either dissolves the crystals (and stones if present), or prevents the crystals from forming by making the urine more acidic. Prescription dog food and prescription cat food can also increase your pet’s water intake to ensure there is improved urinary volume and outflow.

Some crystals like ammonium urate can be managed with special medication, while others like calcium oxalate that have progressed to stone formation will require a surgical procedure to break down or remove the stone.

Best food for urinary crystals

The 'best' urinary diet for you depends completely on what kind of crystal is present. There are actually a few different therapeutic urinary diets, and many of them are only indicated for one, or sometimes 2 types of crystal. For instance, Hills Prescription Diet c/d and Royal Canin S/o are ideal for dissolving and preventing struvite crystals, and preventing calcium oxalate crystal formation, but Hills Prescription Diet u/d is indicated for urate stones. If your pet receives the wrong urinary diet, it may actually make the crystals worse. Therefore, it is vital that you have your pet's urine examined and await instruction from your vet, before choosing a prescription diet.

How can urinary crystals be prevented?

Urinary crystals have the potential to cause your pet pain and discomfort, and in some cases even make them gravely ill. Although some cases are unavoidable, there are preventative measures you can take to protect your pet, particularly if they are a breed known to be predisposed to urinary crystals and stones.

1. Avoid Cheap Pet Food

cat licking lips in front of food bowl

One of the causes of urinary crystals is a poor quality diet, particularly in cats. So it's extra important not to give into temptation and buy the cheap, poor quality supermarket food - you may end up paying much more in vet bills in the long run!

Always ensure that your pet is fed a high quality, scientifically formulated diet, and where possible, one that is proven to support a healthy urinary tract, such as Pro Plan Urinary Care for Cats.

Try A Premium Diet Instead:

(Please note that the below diets are 'everyday' diets, and are not intended for treating existing urinary issues. If your pet has urinary issues, your vet may recommend a urinary cat food for them.)

Hills Science Diet Urinary Hairball

Hills Science Diet Urinary Hairball Control is a dry food formulated for adult cats 1-6 years of age requiring hairball control and urinary system support.

Royal Canin Urinary Care

With balanced levels of dietary minerals, this diet decreases urine pH, creating an environment that is unfavourable to the development of urinary crystals and stones.

Hills Science Diet Dog Food

Hill's Science Diet Dog Food Formulas all provide precisely balanced, high quality nutrition to keep your adult dog happy and healthy.

Pro Plan Dog Food

Pro Plan's premium line of dog food is made from high quality ingredients, and contains all the essential nutrition to keep your dog in great shape with a healthy urinary tract.

2. Keep them hydrated

cat drinking from water fountain

If your pet is hydrated, their urine will be less concentrated, which reduces the formation and growth of crystals. There are a number of ways to increase their water intake - such as feeding wet cat food, providing running fresh water with a cat drinking fountain, and offering broths (not suitable for dogs and cats on prescription urinary diets) and hydration supplements as alternative options to plain water, such as Pro Plan Hydra Care for cats.

3. Budge the pudge

pug dog going to the toilet on grass

Obesity is one of the main predisposing factors to urinary issues, particularly in cats. If your pet is a little pudgy, you can reduce their risk of urinary issues dramatically simply by getting them down to a nice slim bodyweight. Plus, this will also help decrease their risk of arthritis, digestive issues, pancreatitis, and diabetes! You've got nothing to lose, except the excess weight!

Read about easy ways to help your pet lose weight with our articles Obesity in Pets, How to help your dog lose weight and How to help your cat lose weight.

4. Regular vet checks

dachshund having check up at vet

Your pet's annual or bi-annual health check is also a great opportunity to check that everything is going smoothly. If your pet has a history of urinary issues, you may choose to test their urine regularly by bringing along a fresh urine sample in a clean container. This allows your vet to quickly and easily check for the presence of urinary crystals, as well as red and white blood cells, bacteria and other abnormalities.

Further Reading

Want to read more? Check out our other articles:

Feline Lower Urinary Tract Disease in Cats

Urinary Issues in Dogs

Bladder stones in dogs

Preventing Urinary Issues in Your Cat

Why do cats pee on things?