Abstract
We examined patient characteristics and related test results of 15 urine specimens in which ammonium urate (AU) crystals were observed in our hospital in the past 3 years. In 13 of the 15 specimens, the urine was acidic, which was in contrast to most reports in which AU crystals were detected in alkaline urine. When some time has passed before examination, urine may become alkaline. However, examination for urinary sediments has recently been performed rapidly in Japan, which may have led to our present findings. Patients with AU crystals in their urine were younger than those without the crystals (n = 60; 19 years vs 66 years; p < 0.001) and were mostly male (p < 0.05). These findings of younger age and male predominance are consistent with those observed among patients with postrenal failure due to AU stones, suggesting a correlation between AU stones and AU crystals. In addition, the average urine specific gravity was significantly higher in samples with AU crystals than in those without the crystals (p < 0.001). Diarrhea, which causes dehydration, was seen frequently (p < 0.001, compared with controls). The presence of AU crystals in urinary sediments could therefore be indicative of AU calculus disease or dehydration.
