Specimen Requirements
Title
Oxalate, 24 Hour Urine
Specimen Requirement
Patient Preparation:
Patients should refrain from Vitamin C supplements during collection and for 48 hours prior to collection for oxalate.
Collection:
The bladder must be emptied at the start of the collection, that first urine is discarded. Thereafter all urine must be collected in a 24 hour urine jug with 25 mL of 6N HCl at start of collection to maintain pH between 1 and 3. Refrigerate urine during collection (critical). Once 24 hour period is complete, measure the total volume, mix well then aliquot 25 mL of the urine into a sterile screw top cup. Indicate total volume on the cup and on the requisition, send refrigerated.
When requesting 24 hour urine jug, request 6N HCl be added before supply is shipped.
Methodology
Spectrophotometry
Stability
Room temp: Unacceptable, Refrigerated: 7 days, Frozen: 7 days
Reference Range
The reference range is determined by the performing laboratory and will show on the report.
Turnaround
1-3 days performed Tuesday, Friday
Clinical Use
Patients who form calcium oxalate kidney stones appear to absorb and excrete a higher portion of dietary oxalate in urine than do normals. Hyperoxaluria is not uncommon in subjects with malabsorption. Twenty-four hour urine collections for oxalate are indicated in patients with surgical loss of distal small intestine, especially those with Crohn’s disease.
Test Code
24OXW