 In 1981, struvite stones were the most common type in cats, making up 78 percent of submitted samples, with only 2 percent comprising calcium oxalate stones.In the mid 1980s there was a substantial increase in the number of calcium oxalate samples, and between 1994 and 2002, 55 percent of feline stones were calcium oxalate and 33 percent were struvite.This may have been caused by the use of dissolution diets for struvite stones in cats and modification of other diets to prevent struvite crystal formation.