What chemistries should be ordered on a 24 hour urine collection?
Urine chemistries should include:
• Calcium
• Oxalate
• Uric acid
• Phosphorus
• Urine volume: All patients should try to maintain a urine volume of at least 2.5 liters/day.
• Citrate forms a complex with calcium in the urine; thus low urine citrate is a commonly found risk factor for calcium stone formation.
• pH should be measured in a 24-hour urine sample; low pH is a risk factor for uric acid stones, and high pH is a risk factor for calcium phosphate stones.
• Creatinine should be measured in all timed urine specimens to ensure that the urine specimen was collected properly.
