Urinary crystals can be a serious health issue for cats. There are several different types of crystals that can form.
Struvite crystals — magnesium ammonium phosphate — used to be the most common type of urinary crystal in felines. Twenty years ago, approximately seventy-five percent of urinary crystals were struvite crystals! As a result, prescription diets used to focus on preventing struvite crystals. The diets were low in magnesium. It worked — by the late 1990s, struvite crystals were to blame for less than fifty percent of urinary crystal problems.
Still, struvite crystals are the most common urinary crystal seen in cats. Many factors contribute to the formation of struvite crystals, including:
- pH of the urine — lower acid levels encourage struvite formation
- Amount of magnesium and phosphorus excreted in urine
- Length of time urine stays in the bladder
- Concentration of urine
The second most common type of urinary crystal is oxalate — calcium oxalate. These crystals form in more acidic urine — the type of urine caused by a diet low in magnesium. In the 1980s, oxalate crystals were responsible for less than five percent of cases; by the late 1990s, oxalate crystals were to blame for forty percent of urinary crystal issues in cats.
Some of the factors that encourage the formation of oxalate crystals are things that prevent the formation of struvite crystals!
- pH of the urine — higher acid levels encourage oxalate formation
- Some breeds have a genetic disposition to forming oxalate crystals
Other types of crystals do exist, but are very rare. Nearly ninety percent of cats with urinary crystals have either struvite or oxalate crystals. A urine test can help your vet determine what type of crystals your cat has — and what treatment is appropriate.
In some cases, crystals can gather together and form stones. Stones have a much higher risk of completely blocking the urinary tract! Struvite stones may be treated with dietary changes; oxalate stones may require surgical removal.