Calcium Oxalate Struvite Crystals In Cats

The crystals themselves can be perfectly normal but become problematic when they combine to form grit or stones of varying shapes and sizes.

Calcium oxalate struvite crystals in cats.

Most calcium oxalate stones develop in cats between ages 5 and 14 years. How calcium oxalate crystals form. Struvite crystals are microscopic crystals that are found in the urine of some cats. 35 of cats with calcium oxalate bladder stones have elevated blood calcium hypercalcemia.

Less common stones include ammonium biurate cystine and uric acid. 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. Unfortunately this change isn t simply due to a decrease in the number of struvite stones. Cats who have had calcium oxalate crystals are at increased risk of a recurrence.

Once the stone is formed it increases in size over weeks or months. 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. Protocols must be put in place to decrease the incidence after initial treatment. Male domestic short haired medium haired and long haired cats appear to be 1 4 times more likely to develop a calcium oxalate urolith than a struvite urolith while both male and female purebred cats eg persian himalayan burmese ragdoll cats appear to be at risk.

Struvite crystals develop in concentrated urine once the urine becomes supersaturated crystals aggregate to form stones. Because struvite or magnesium ammonium phosphate crystals formed because of too much alkalinity in the feline diet commercial pet food manufacturers began acidifying their products. A generation ago struvite crystals and stones were commonly found in cats with urinary tract disease with calcium oxalate stones and crystals relatively rare. Struvite and calcium oxalate are the most common type of stones in cats.

The very diets we use to dissolve struvite have put cats at increased risk for calcium oxalate stones. Cats with calcium oxalate bladder stones tend not to have crystals in their urine while those with struvite stones do tend to have struvite crystals in their urine. The cornerstone of treatment is to increase water consumption to dilute the urine and promote urine specific gravity of less than 1 020 and urine ph of 6 8 7 5. To reduce the incidence of struvite stone formation the cats were fed diets that had lower amounts of magnesium.

Although this diet did benefit many pets several cats started developing calcium oxalate stones due to the dietary change.