One of the most common feline health emergencies we see at FACE is urinary blockages caused by uroliths—crystals or stones that form in the bladder and then obstruct the urinary tract.

Urinary obstructions, most often seen in male cats, are life-threatening emergencies because toxins build up in the body of cats that are unable to urinate.

A recent article in the Journal of Veterinary Internal Medicine describes the composition of uroliths in cats, and the risk factors for their formation, based on a study of nearly 4,000 cases between 2005 and 2018.

Here’s a summary of the key points.

The percentage of struvite uroliths has been increasing over the time range studied, from 41.8% to 54.5%. Cases of calcium oxalate uroliths have been declining, from 50.1% to 37.7%. A third kind of stone that contains urate accounts for around 10% of cases.

Why has the composition of stones been changing over the past several years? The researchers think it has to do with environmental and dietary changes. The amount of acidity in a cat’s diet can influence stone formation.

Cats that are prone to urinary blockages are often prescribed veterinary diets that are formulated to prevent crystals. The researchers say more studies are needed to understand how the growing popularity of homemade pet food is influencing crystal formation.

What are the most common risk factors for urinary blockages in cats?

Crystals can form in both male and female cats, but males are more likely to experience urinary blockages than females.

Calcium oxalate uroliths are more commonly seen in older cats, in the 7-15 years of age range. Struvite uroliths are more common in cats that are in the 4-10 years of age range.

The breeds most likely to experience calcium oxalate uroliths are the Burmese and Persian. Domestic medium-haired cats are more likely to develop struvite crystals than domestic shorthairs. Bengals, Ocicats, and Persians are at lower risk for struvite formation.

What can you do to prevent urolith formation in your cat? Talk to your veterinarian about diets that promote urinary tract health. Cats with a history of crystals can benefit from a prescription diet.

Keep an eye on your cat’s litter box habits. If you notice frequent trips to the box with signs of distress and little to no urine production, be sure to take your cat to the vet as soon as possible.