Asian Journal of Case Reports in Medicine and Health

Background: Ammonium bi-urate crystals are rarely seen on routine urine microscopy, particularly in older children. “These crystals may appear in condition like dehydration or mild infection when urinary chemistry changes. Timely identification helps clinicians prevent later stone development.

Case Report: A 10-year-old boy presented with low-grade fever (100.2°F) and mild dehydration, but no urinary symptoms. Urine microscopy revealed numerous refractile, brownish-yellow “thorn-apple” crystals at near-neutral pH, which is consistent with ammonium bi-urate. The urine culture was sterile, and renal function test results were normal. He was advised to increase oral fluids, and on review after three months, the crystals had completely disappeared.

Discussion: Ammonium bi-urate crystalluria occurs when the urinary ammonia and urate concentrations increase under near-neutral pH conditions. Transient metabolic stress or reduced fluid intake can precipitate such crystals even in the absence of infection. Although historically observed in regions with a high prevalence of bladder stones and low phosphate diets, sporadic cases may occur in otherwise healthy children. Early recognition and hydration remain key to preventing stone disease progression.

Conclusion: This manuscript highlights a rarely documented occurrence of ammonium bi-urate crystalluria in an older child, an observation with important diagnostic and preventive implications. Awareness of such cases can guide clinicians toward intervention through simple measures like hydration. It can also save excessive use of antibiotics specially in the absence of infection.