Oxalate, Urine

Specimen requirement 24 Hr urine (for adult patients only):

U2 bottle

Spot urine (for paediatric patients only):

Plain bottle

Volume: 10 mL
Authorisation code required No
24 Hr available service No
Precaution Avoid excessive amounts of vitamin C or vitamin C rich food for at least 48 Hr before and during urine collection.
Method Liquid chromatography mass spectrometry (LCMS)
Reference interval

Adult (> 18 years)

Adult male: 0.08 - 0.49 mmol/day
Adult female: 0.04 - 0.34 mmol/day

(Source: Trinity Biotech oxalate kit insert)

Remarks: Please note that the current reference intervals are established in clinically healthy subjects. Since oxalate excretion decreases in proportion to the decrease in renal function, results obtained from patients with renal impairment should be interpreted with caution.

Children:
Age Urine Oxalate / Creatinine Ratio (mmol/mol Cr)
< 7 months < 360
7 months - < 2 years < 174
2 - < 5 years < 101
5 - < 16 years < 82
> 16 years < 40

(Source: Nat Rev Nephrol. 2012 Jun 12;8(8): 467 - 75)

Clinical indication Diagnosis of primary or secondary hyperoxaluria in patients with renal calculi
Result interpretation

Oxalate is a normal constituent of urine, it is derived from endogenous and dietary sources.

An increased excretion of oxalate can be attributed to increases in ingestion of oxalate precursors or oxalate rich foods, formation of oxalate due to metabolic defects such as in primary hyperoxaluria, and absorption of oxalate in a number of gastrointestinal disorders that produce severe fat malabsorption.

Formation of the sparingly soluble calcium salt of oxalate in the urinary tract is thought to be the major factor in urolithiasis.

Very high levels are also seen in patients with ethylene glycol poisoning.

See also urine organic acids.
Measurement of uncertainty See table.
Frequency of measurement Biweekly