In the majority of uric acid stones, however, the urine itself is so persistently acidic that even normal amounts of uric acid can precipitate and form stones. Conditions that predispose one to highly acidic urine include gout, chronic diarrhea, and dehydration. Causes of Struvite Stones Struvite stones are almost always caused by urinary tract infections due to bacteria that secrete certain enzymes. These enzymes, in turn, raise urine concentrations of the ammonia that composes the crystals forming struvite stones. The stone-promoting bacteria are usually Proteus, but may also include Pseudomonas, Klebsiella, Providencia, Serratia, and staphylococci.
Women are twice as likely to have struvite stones as men.
Causes of Other Stones Other stones, including cystine and xanthine stones, are usually due to genetic abnormalities. Cystine stones are found in patients with an inherited disorder that causes abnormal transport in the kidney and gastrointestinal system of the amino acids cystine, ornithine, lysine, and arginine. In some cases, xanthine stones may develop in patients being treated with allopurinol for gout.