Citrate, Urine

Diagnostic Use

Urinary citrate is a major inhibitor of kidney stone formation due in part to binding of calcium in urine. Low urine citrate levels are considered a risk factor for kidney stone formation. Several metabolic disorders are associated with low urine citrate. Any condition that lowers renal tubular pH or intracellular pH may decrease citrate e.g., metabolic acidosis, increased acid ingestion, hypokalaemia, or hypomagnesemia. Urine citrate measurement may be used to diagnose risk factors for patients with calcium kidney stones and to monitor result of therapy in patients with calcium stones or renal tubular acidosis.

One of the main functions of the kidney and urinary tract is to dispose of waste products and excess ions in a soluble form. Certain combinations of these ions, however, are only sparingly soluble in urine and sometimes precipitate. The precipitates may become lodged in the urinary tract and form a nucleus around which a stone may grow. Most renal stones are passed spontaneously (65%). The prevalence of kidney stones seems to depend on many factors including diet, climate, genetic variability, and underlying disease (e.g., infection, hyperparathyroidism, renal tubular acidosis).

Most stones are usually composed of calcium oxalate (58%) or calcium phosphate (14%) or a combination of these (9%) in Christchurch. Others are due to infection with urea splitting bacteria, excess uric acid (10%), or cystine (0.6%).

Department

Lipids/Trace Metals

Delphic Registration Code

UCIT

Laboratory Handling

Separating

Take aliquot for UCRN please

Laboratory

Sample needs to be acidified to be acceptable for analysis. Please confirm pH is less than 4 before sending to CHL. Make sure 24 hour urine volume is provided on the form or sample.

Test Adds

Refrigerated (preferred) 14 days, frozen 14 days

Turnaround Time

7 days

Test Code

4519