Ammonium urate urinary stones.

Until the last century, ammonium urate stones were quite common in preindustrial Europe. In contemporary practice these stones are found in developing countries, and are associated with uric acid and ammonium-enriched urine. Such conditions may occur with a) urealytic infection, resulting in mixed ammonium urate/magnesium ammonium phosphate precipitates and b) urinary phosphate deficiency of alimentary origin, resulting in precipitates free of magnesium ammonium phosphate, in sterile urine. The latter situation is closely related to a diet poor in phosphate and to a low fluid intake common in endemic lithiasis areas. Ammonium urate and uric acid have different solubility patterns dependent on pH, and consequently treatment will be different in each case.