Metabolic syndrome and the genesis of uric acid stones.

Uric acid stones are significantly more common among nephrolithiasis patients with type 2 diabetes, obesity, and/or the metabolic syndrome. The principal metabolic feature responsible for this association is an overly acidic urine, which leads to the precipitation of sparingly soluble uric acid crystals in urine and subsequent development of stones. The unduly acidic urine in uric acid stone formers is caused by a combination of excessive dietary intake of animal proteins and a defect in renal ammoniagenesis and/or excretion that leads to impaired buffering and amplifies the acidic urine caused by an increased acid excretion.