Urinary crystals in cats

Content by Emma Chandley BVetMed PGCertSAS MRCVS 

Urinary crystals are tiny mineral formations that develop in your cat’s urine. Under normal circumstances, urine contains dissolved minerals that pass out of the body without issue. When conditions change – for example, the urine becomes more concentrated or the pH of the urine changes – these minerals can begin to form crystals.

There are several types of crystals, but the most commonly seen in cats are struvite and calcium oxalate. In small numbers, they may not cause any noticeable problems. However, when they build up, they can irritate the lining of the bladder and urinary tract, leading to discomfort and inflammation.

In some cases, crystals can combine to form larger stones or contribute to blockages within the urinary tract. This is particularly significant in male cats, where the urethra is narrower. If the urethra becomes blocked, this is a medical emergency. 

• Urinary crystals are mineral deposits that form in the urine
• Common types of crystals  include struvite and calcium oxalate
• They can cause irritation to the bladder and urinary tract
• In some cases, they contribute to stone formation or blockages
• Early recognition and management can help to prevent complications

Urinary crystals tend to form when the balance within the urine changes. This can happen for several reasons, often overlapping with each other rather than acting in isolation.

Diet plays an important role. The mineral content of food, along with how it influences urine acidity, can affect crystal formation. Hydration is another key factor. Cats that drink very little water produce more concentrated urine, which increases the likelihood of crystals developing.

Stress can also contribute, particularly in indoor cats. It is closely linked with a condition known as feline lower urinary tract disease (FLUTD), where inflammation of the bladder creates an environment in which crystals are more likely to form. Other contributing factors may include obesity, reduced activity levels, and underlying medical conditions that alter urine composition.

Urinary crystals can affect any breed of cat. That said, some patterns are seen more commonly in practice. Male cats are at higher risk of complications, particularly blockages, due to the narrower shape of their urethra. Certain pedigree breeds, such as Persians and Burmese, may also be more predisposed to urinary tract issues – although this is not exclusive.

Lifestyle factors often play a greater role than breed alone. Indoor cats, those with lower water intake, and cats with a more sedentary and less active routine are more frequently affected.

In the earlier stages, the signs first seen by owners are often related to bladder irritation.

You may notice your cat:

• Visiting the litter tray more frequently
• Passing smaller amounts of urine
• Straining or taking longer to urinate
• Passing urine outside the litter tray
• Showing signs of discomfort when urinating
• Having blood-tinged urine

Some cats also become more withdrawn or unsettled, particularly if the irritation is ongoing.

Diagnosis

Diagnosis usually starts with a full clinical examination and a detailed discussion about what has been noticed at home.

A urine sample is a very important part of the diagnosis. Testing the urine will allow your vet to assess the concentration of the urine – the pH – and the presence of crystals under a microscope.

In some cases, additional tests such as imaging may be recommended to assess the bladder wall, and look for stones or other abnormalities – plus check for any underlying issues.

The main aim of treatment is to correct the underlying conditions that are allowing crystals to form. Dietary management is often a key part of the treatment plan. Specially formulated urinary diets can help dissolve certain types of crystals – particularly struvite – and also reduce the risk of recurrence.

Encouraging increased water intake is also important, whether through wet food, multiple water sources, or water fountains.

Pain relief and anti-inflammatory medication can also often be prescribed to improve comfort while the bladder settles. Where stress is a contributing factor, environmental changes and management of stressors (wherever possible) can make a significant difference.

Prognosis

With appropriate management, the outlook for mild to moderate cases of urinary crystals is generally very good. Many cats respond well to dietary changes and supportive care, particularly when the condition is identified early. Ongoing management and close monitoring is often needed to reduce the risk of recurrence.

More severe cases are usually associated with obstruction of the urinary tract, which is a medical emergency.

Signs may include:

• Repeated attempts to urinate with little or no output
• Vocalising or clear signs of pain
• Vomiting
• Lethargy or collapse
• A firm, enlarged bladder

This situation can deteriorate quickly and requires urgent veterinary attention.

Diagnosis

Diagnosis is based on clinical examination, often alongside imaging and blood tests to assess the overall impact on the body. An obstructed bladder is usually apparent very quickly on examination, and further tests help determine the severity and then guide treatment.

The main aim of the treatment is to quickly and safely remove the obstruction and stabilise the patient. This typically involves passing a urinary catheter under sedation or anaesthesia to unblock the urethra. Intravenous fluids are given to correct dehydration and support kidney function.

Once the immediate crisis has been managed, further steps are taken to reduce the risk of recurrence. This may include dietary changes, ongoing monitoring, and in some cases surgical options if blockages keep happening.

Prognosis

When treated promptly, many cats recover well from an episode of obstruction. Unfortunately recurrence is common, this is especially true if there is no long-term management in place. Early intervention tends to result in a better outcome.

“Urinary issues in cats are something we see very regularly in practice, and they can range from mild irritation through to genuine emergencies. One of the more challenging aspects is that the early signs can be quite subtle. There may just be a few extra visits to the litter tray, or a slight change in behaviour, and it can be easy for owners to miss. 

“Crystals themselves are only part of the picture. They often develop alongside inflammation within the bladder, and it’s that combination that leads to the clinical signs owners notice at home.

“What makes the biggest difference in my experience is picking things up early. When cats are seen at the stage where signs are still mild, treatment is usually straightforward and very effective. Once a blockage develops, the situation becomes far more serious, so recognising those early changes is key.”

Emma Chandley BVetMed PGCertSAS MRCVS 

If you’re thinking about getting a Petgevity Lifetime Plus policy, we’ll consider all pre-existing conditions when offering cover for your cat*. 

When you apply for cat insurance, you need to let us know: 

• Which medical conditions they’ve had in the last two years – including those which need ongoing treatment, monitoring or check-ups

• Their health status now

Find out more about Petgevity’s cat insurance for pre-existing conditions.