Urinary Crystals in Cats: Causes and Symptoms

While it may sound quite exciting when you find out that your cat is producing crystals, urinary crystals are a far cry from the valuable gemstones and diamonds you may be picturing!

Unfortunately, rather than making you money, they are much more likely to end up costing you a pretty penny.

What Are Urinary Crystals?

Urinary crystals are microscopic structures that can be found in the urine of many animals, including cats. Some normal animals can have crystals in their urine, although sometimes they are indicative of an underlying issue, especially if present in large numbers or accompanied by urinary symptoms.

It is important to note that urinary crystals and urinary stones are not the same thing, though many will use the terms interchangeably. It’s true that urinary stones are made out of crystals, but the presence of crystals does not guarantee that stones are present.

Crystals are gritty and can irritate and inflame the sensitive urinary tract, leading to a number of problems. They are tiny and individual crystals cannot be seen with the naked eye. Stones, on the other hand, can be very large and can look like smooth pebbles.

They come in a range of shapes, colors, and sizes and some vets are known to keep stones that they have removed from patients as ‘souvenirs’!

Vets and owners should be aware that a large number of crystals can naturally form in a urine sample that has been left standing, especially if in the fridge. So, if an owner brings in a urine sample that was taken yesterday and was kept in the fridge overnight, the vet is sure to find lots of crystals, whether or not the cat is forming them themselves.

The most common types of crystals we see in our feline friends are:

  • Struvite
  • Calcium oxalate

These crystals are easy to distinguish from each other when viewed under the microscope and have different causes and treatment methods.

Symptoms of Urinary Crystals In Cats:

A cat with urinary crystals may show a multitude of signs and cats are affected to varying degrees.

  • Initially, an owner may notice that the cat is spending more time in the litter tray and is straining to go. Many owners will actually confuse this behavior with constipation, as the posture cats go in to can make it appear like the cat is struggling to defecate.
  • They may be peeing in drips and drops and the urine may even be pink-tinged and stronger smelling than usual. Often, they will be peeing a lot more than they normally would and will drink more water to compensate for this.
  • One frequent problem we find is that cats will start to mess around the house. Cats who have been litter-trained for years will suddenly urinate beside their tray, in a bed, or perhaps in the family bathtub. This is one of the most common cat behavior problems. However, by finding the root cause and proper management, most cats will stop this behavior.
  • Cats tend to be quite uncomfortable and may even vocalize or howl when passing urine. In an attempt to ease their discomfort, some will over-groom their hind end, and owners may notice bald patches or reddened skin near the genital area.
  • Though some cats are not overly affected by their crystals, others may be quite out of sorts and it is not unheard of for a cat to become withdrawn, lose their appetite and spend more time away from people.

Worryingly, crystals can actually cause a blockage in some cats. This is more of an issue in male cats as their ‘plumbing’ is a lot narrower! When a cat is unable to pass urine due to a blockage, they can become very sick in a short amount of time.

These cats will be constantly trying to pass urine but, if you look closely, nothing will be coming out. They will be distressed and may have a tense or bloated abdomen, caused by their enlarged bladder.

The sooner these cats are brought to the clinic the better their prognosis, as waiting too long can lead to acute renal failure and even bladder rupture.

Causes of Urinary Crystal Formation:

  • Some cats are more prone to forming urinary crystals than others. We know that cats who do not drink a lot and who eat dry kibble rather than wet food are over-represented. This makes sense as crystals will precipitate in concentrated urine. The more dilute the urine, the less chance the crystals have of forming.
  • Certain foods are linked to the formation of crystals, and those fed diets that are not nutritionally balanced or too high in certain minerals may suffer.
  • Similarly, owners who supplement their cats with un-needed minerals such as Calcium, may be inadvertently causing issues.
  • Cats should naturally have a very low (acidic) urinary pH, and a pH over seven (an alkaline pH) can encourage certain types of crystals to form. Certain diets can cause urinary pH to rise and can be the cause of crystals forming. Typically, we are aiming for a pH of between six and seven, and there are strips available which can be used to measure this number at home.
Let’s take a closer look at struvite crystals

Struvite crystals are formed from magnesium, ammonium, and phosphate. It is easy to recognize these crystals under a microscope as they have a characteristic ‘coffin box’ shape.

Image Source

As mentioned, many normal cats who do not have urinary disease will have some struvite crystals present in their urine. There are certain types of bacterial urinary infections that can promote the presence or struvite crystals, so it is always prudent to check for infection if these crystals are present.

Calcium Oxalate crystals, on the other hand, are usually present when urine is too acidic. A cat affected with struvite crystals, calcium oxalate crystals (or any other type of crystal) will suffer from the same array of symptoms and are affected in the same way.

However, it is important to know which crystals a cat has so that we can tailor our treatment, as the crystals form for different reasons and respond to different therapies.

When a cat is starting to display the symptoms associated with urinary crystals, the best thing to do is have them assessed by a vet. If a cat has suffered from urinary issues in the past, there will be a high suspicion that history is repeating itself as many patients are repeat offenders.

The vet will want to check them over, ensuring they are well hydrated and that their kidneys feel normal. They will be sure to check the bladder, however, sometimes the bladder is so small from all of the straining that it is difficult to locate! The bladder wall may be thickened and irritated and some cats will resent it being touched.

The next step is to take a urine sample. There are several ways of doing this, some easier than others!

Sometimes, particularly if a cat is difficult to handle or always has an empty bladder at the vets, an owner will be sent home with a special type of non-absorbent cat litter. This is placed in a clean tray and, when the cat urinates, the pee can be sucked into a syringe and transferred into a container. The best sample to collect is the first urination of the day and the sample should be brought into the vet immediately.

Another option is for the vet to manually express the bladder, which means gently pressing on it to encourage urination. However, this requires the bladder to contain some urine and the cat needs to be quite co-operative.

The final method of urine collection is called ‘Cystocentesis’. This involves popping a tiny needle into the bladder in order to collect a sterile sample of urine. This is especially useful when trying to determine if a urinary infection is present as there should be minimal contamination. Some vets may use an ultrasound to help them locate the bladder and to ensure they insert the needle in the right place.

A urine sample is typically examined within the veterinary clinic using dipstick tests, a refractometer and a microscope. The dipstick will check for the presence of things like blood and glucose and can also determine the pH. The refractometer allows us to know the concentration of the urine.

Finally, the microscope is used to examine spun-down urine and to check for the presence of crystals. Urine may also be sent away to an external laboratory to run some more specific tests, such as urine cultures to check for infections.

Once the problem has been identified, treatment can begin. While most diets for urinary cat issues are prescribed, you can try some non-prescribed cat food substitutes as a home remedy. Our next article in this series focuses on the treatment of crystals and how to prevent them.

Dr. Kate Davis is a veterinarian with almost ten years of experience. Dr. Kate has always had an affinity for cats, so it was a short step for her to become a cat writer.

  1. Thanks for sharing such an informational article! It has really helped me understand my cat better than before.

  2. Thank you for drawing my attention to this problem, which hadn’t occurred to me. I will be more careful about my cat’s diet from now on!

  3. I’ve heard this twice from Vets: feeding hard kibble type food to cats can encourage the development of either the stones or the crystals. Consequently I give only the canned meal accompanied by strips of baked chicken hopefully this will help to maintain a healthier overall diet. Currently looking for something for them to chew enabling cleaner teeth.

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