Citrate, Urine

Diagnostic Use

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 (urolithiasis).

Most renal stones are passed spontaneously (65%). Those trapped in the kidney or lower urinary tract can cause serious anatomical damage, partial or total obstruction of urine flow, and excruciating pain for the patient. The estimated prevalence varies from about 1.5% of the general population in UK to 12% in USA6 and seems to depend on many factors including diet, climate, and genetic variability and underlying disease such as infection. A high intake of animal protein increases urinary excretion of calcium and oxalate, and the increase in purine consumption increases the excretion of uric acid. Incidence increases with ambient temperature mainly due to decreased urine volume. Diseases such as hyperparathyroidism and renal tubular acidosis (failure to acidify urine) can also lead to urolithiasis. Hospital admissions due to stone formation in New Zealand are 7.6 per 10,000 head of population.

Most stones are usually composed of calcium oxalate (58%) or calcium phosphate (14%) or a combination of these (9%) in Christchurch (refer to Woods et al poster in appendix). Others are due to infection with urea splitting bacteria (causes alkalization of urine and calcium phosphate and magnesium ammonium phosphate precipitation), excess uric acid (10%), or cystine (0.6%).

Low urinary citrate is subject to therapy by correcting acidosis, hypokalemia, or hypomagnesemia by altering diet or using drugs such as citrate and potassium.


Lipids/Trace Metals

Delphic Registration Code


Laboratory Handling


Take aliquot for UCRN please


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

Stable refrigerated for 14 days.

Turnaround Time

1 week

Test Code