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PTD - 326 

Test Directory -  Urinary Citrate (24hr)

Clinical Indications

Citrate is an important inhibitory substance in the urinary tract which forms soluble complexes with calcium. It reduces the saturation of calcium phosphate and calcium oxalate, inhibiting crystallization and enlargement of kidney stones. As a result, it decreases the formation of calcium containing stones.
Urine citrate may be measured in renal stone patients at diagnosis and is used to monitor treatment with potassium citrate.

Request Form 

Combined Pathology Blood form (Yellow/Black or Blue for GP's)

Availability

Referred Test: Analysed by Clinical Biochemistry, UCLH if specific criteria met.

Specific Criteria

Requested as part of a metabolic screen in patients with renal calculi.

Patient Preparation

None

Turnaround Time

2 weeks

Specimen

24 hour urine collection into acid preservative

Container

Acidified 24 hour urine container. May be done on same sample collection as urinary citrate.

Causes for Rejection

Non-acidified urine collection. Unlabelled sample.

Reference Range

 

Urine citrate 24hr excretion (mmol/24hr):

Male 0.6 - 4.8; Female 1.3 - 6.0.

Urine citrate:creatinine ratio (mmol/mmol creat):
Male 0.04 - 0.33; Female 0.11 - 0.55.

Reference; Referral laboratory (UCLH)

Interpretation

 

Hypocitraturia is often observed in patients with idiopathic kidney stones. Several reports have shown that patients with calcium oxalate calculi have lower citrate excretion than control subjects. A low citrate is associated with renal tubular acidosis, low potassium, chronic diarrhoea, UTI.

Lab. Handling

Processing: Record the 24hr volume, aliquot and store at 4C in separating fridge (CB39) in the 'urine odds' rack until they are packaged up and sent to the referral laboratory.

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Version 1.0 / November 2014                                                                                                Approved by: Consultant Biochemist