Renal stone disease may ensue from either derangements of urine biochemistries or anatomic abnormalities of kidneys and urinary tract.
Genetic, environmental and dietary factors may also cooperate in the pathophysiology of nephrolithiasis.
An adequate metabolic evaluation should focus on the urinary excretion of promoters and inhibitors of stone formation as well as on the occurrence of systemic diseases potentially related to secondary nephrolithiasis (i.e., endocrine disturbances, malabsorption, bone diseases). Moreover, metabolic investigations should provide reliable information on patient’s dietary habits, guide towards the best therapeutic approach and enable the physician to verify patient’s compliance to prescribed therapies.
An extensive metabolic evaluation is recommended in patients with active stone disease (namely, at least one new stone within the last two years), or in those having had a single stone episode occurred in peculiar conditions: familial history of disease, childhood, menopause, pregnancy, systemic diseases. Simplified protocols may be adequate in non-active nephrolithiasis or in patients with single stone and no relevant risk factors.
A 24 hour urinary stone profile typically contains measurement of:
Calcium, Phosphate, Urate and Oxalate
However, measurement of magnesium, citrate and cystine may also be of use in certain stone formers.
Oxalate. Citrate, Calcium, Magnesium, Phosphate - 24 h urine collection into an acid (red) bottle.
Urate and cystine - 24 h urine collection in plain (black) bottle.
Oxalate. Citrate, Calcium, Magnesium & Phosphate may also be analysed from a 24 h plain collection so long as the urine is acidified on arrival in the laboratory. If only a single plain 24 h collection is received and all above tests are requested:
1. Record volume of collection
2. Take aliquot for tests that require plain (non acidified sample)
3. Acidify the whole 24 hr urine sample accoring to the SOP, mix well and leave for approx 5-10 min, mix well again and aliquot for tests that require an acidified sample.
4. When sending to UCLH for oxalate, citrate or cystine measurement please specific only the tests which need to be performed.
Further information on the specific tests may be found in the related tests section.
Reference range for all analytes provided by referral laboratory.