The presence of ammonium urate crystals is generally of little clinical significance. They are found in acidic urine (pH less than 6.5). The formation of ammonium urate crystals can be caused by a combination of factors including decreased urine volume or a condition that alkalinizes (increases the pH of) urine, such as a vegetarian diet, urinary tract infection or some medications. They are also found in individuals who have gout and during some chemotherapy treatments.
In individuals who have kidney stones, the repeated presence of ammonium urate crystals in urine may indicate, if applicable, the probable nature of the stones. It should be noted, however, that most patients with ammonium urate crystals will never form stones.