Calcium urine
Description:
The urine calcium:creatinine ratio is often used to assess hypercalciuria in hypercalcaemic patients
Clinical details:
Calcium excretion is handled by the GI tract and the kidneys. The gut secretes approximately 2-3 mmol calcium per 24 h into faeces via the digestive juices. The kidneys filter approximately 250 mmol/24 h, with 98 % being reabsorbed.
Factors increasing tubular calcium resorption include thiazide diuretics, hypovolaemia and alkalosis; volume expansion, acidosis and loop diuretics all increase urine calcium concentrations.
The urine calcium:creatinine ratio is often used to assess hypercalciuria in hypercalcaemic patients, e.g. due to primary hyperparathyroidism (PHPT). Unlike in PHPT, patients with Familial Hypocalciuric Hypercalcaemia (FHH) have low urine calcium levels compared with serum.
NB. The most appropriate test to investigate for FHH is a 24 hour urine to calculate the urine calcium/creatinine clearance ratio (UCCR), which is a different calculation to the urine calcium:creatinine clearance ratio and requires a 24 hour urine sample and blood test.
The following equation is used to calculate the urine calcium:creatinine ratio in the laboratory:
Calcium:Creatinine ratio = Urine Calcium (mmol/L) / Urine Creatinine (mmol/L)
Factors increasing tubular calcium resorption include thiazide diuretics, hypovolaemia and alkalosis; volume expansion, acidosis and loop diuretics all increase urine calcium concentrations.
The urine calcium:creatinine ratio is often used to assess hypercalciuria in hypercalcaemic patients, e.g. due to primary hyperparathyroidism (PHPT). Unlike in PHPT, patients with Familial Hypocalciuric Hypercalcaemia (FHH) have low urine calcium levels compared with serum.
NB. The most appropriate test to investigate for FHH is a 24 hour urine to calculate the urine calcium/creatinine clearance ratio (UCCR), which is a different calculation to the urine calcium:creatinine clearance ratio and requires a 24 hour urine sample and blood test.
The following equation is used to calculate the urine calcium:creatinine ratio in the laboratory:
Calcium:Creatinine ratio = Urine Calcium (mmol/L) / Urine Creatinine (mmol/L)
Reference range:
See Chemistry Reference Ranges Document at Automated Chemistry Laboratory at Guy's and St Thomas'
Units:
mmol/L
Department:
Location:
Sample type and Volume required:
30mL aliquot from 24 hour urine with 10mL 0.1N Hcl
Turnaround time:
2 days
Storage and transport:
30mL aliquot from 24 hour urine with 10mL 0.1N Hcl
Time limit for extra tests:
Urine calcium:creatinine ratio (CACR) will be calculated when both urine calcium and urine creatinine are requested. CACR is not currently accredited by UKAS.
Contacts:
Blood Sciences Department-Guy's And St Thomas' Hospital
St Thomas' Hospital
North Wing - 5th Floor
Westminster Bridge Road
London SE1 7EH
Contact: 020 7188 9247
Guy's Hospital
Southwark Wing - 4th Floor
Great Maze Pond
London SE1 9RT
Contact: 020 7188 4781
North Wing - 5th Floor
Westminster Bridge Road
London SE1 7EH
Contact: 020 7188 9247
Guy's Hospital
Southwark Wing - 4th Floor
Great Maze Pond
London SE1 9RT
Contact: 020 7188 4781
Automated Chemistry Laboratory at Guy's and St Thomas' Clinical Advisory Service
Monday – Friday, 09:00-17:00 h: 07738897061
Out of hours, weekends & bank holidays: find details on Rotawatch on Trust intranet GTi, or contact via GSTT switchboard.
Out of hours, weekends & bank holidays: find details on Rotawatch on Trust intranet GTi, or contact via GSTT switchboard.
Last updated: 19/01/2022
