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Test ID: RAMBO Ammonium, Random, Urine

Useful For

Diagnosis of the cause of acidosis using random urine specimens

 

Diagnosis and treatment of kidney stones

Method Name

Enzymatic

Reporting Name

Ammonium, Random, U

Specimen Type

Urine


Specimen Required


Supplies: Sarstedt 5 mL Aliquot Tube (T914)

Container/Tube: Plastic tube

Specimen Volume: 4 mL

Collection Instructions:

1. Collect a random urine specimen.

2. No preservative.


Specimen Minimum Volume

1 mL

Specimen Stability Information

Specimen Type Temperature Time Special Container
Urine Refrigerated (preferred) 14 days
  Frozen  14 days
  Ambient  72 hours

Clinical Information

The kidney regulates acid excretion and systemic acid base balance. Changing the amount of ammonium in the urine is one important way the kidneys accomplish this task. Thus, measuring the urine ammonium level can provide understanding of the cause of an acid base disturbance in individual patients.(1-3)

 

The urine ammonium level can also provide a lot of information about the daily acid production in a given patient. Since most of an individual's acid load comes from ingested protein, the urine ammonium is a good indicator of dietary protein intake.

 

Urine ammonium measurements can be particularly helpful for the diagnosis and treatment of kidney stone patients:

-High urine ammonium and low urinary pH suggests ongoing gastrointestinal losses. Such patients are at risk of uric acid and calcium oxalate stones.

-Low urine ammonium and high urine pH suggests renal tubular acidosis. Such patients are at risk of calcium phosphate stones.

-Patients with calcium oxalate and calcium phosphate stones are often treated with citrate to raise the urine citrate (a natural inhibitor of calcium oxalate and calcium phosphate crystal growth). However, citrate is metabolized to bicarbonate (a base), which can increase the urine pH. If the urine pH gets too high, the risk of calcium phosphate stones may have unintentionally been increased. Monitoring the urine ammonium concentration is one way to titrate the citrate dose and avoid this problem. A good starting citrate dose is about one-half of the urine ammonium excretion (in mEq of each). One can monitor the effect of this dose on urine ammonium, citrate, and pH values, and adjust the citrate dose based upon the response. A fall in urine ammonium should indicate whether the current citrate is enough to partially (but not completely) counteract the daily acid load of that given patient.(4)

Reference Values

Random: 3-65 mmol/L

No reference values established for <18 years and >77 years of age.

Interpretation

If a patient has acidosis and the amount of ammonium in the urine is low, this is suggestive of a renal tubular acidosis.

 

If the amount of ammonium is high, this suggests that the kidneys are working normally and that there are other losses of bicarbonate in the body. Typically this implies gastrointestinal losses.

Clinical Reference

1. Peonides A, Levin B, Young W: The renal excretion of hydrogen ions in infants and children. Arch Dis Child. 1965 Feb;40(209):33-39

2. Kamel KS, Briceno LF, Sanchez MI, et al: A new classification for renal defects in net acid excretion. Am J Kidney Dis. 1997 Jan;29(1):136-146

3. Madison LL, Seldin DW: Ammonia excretion and renal enzymatic adaptation in human subjects, as disclosed by administration of precursor amino acids. J Clin Invest 1958. Nov;37(11):1615-1627

4. Coe FL, Evan A, Worcester E: Pathophysiology-Based Treatment of Idiopathic Calcium Kidney Stones. Clin J Am Soc Nephrol. 2011 Aug;6(8):2083-2092

Day(s) Performed

Monday through Sunday

Report Available

Same day to 2 days

CPT Code Information

82140

LOINC Code Information

Test ID Test Order Name Order LOINC Value
RAMBO Ammonium, Random, U 1842-4

 

Result ID Test Result Name Result LOINC Value
RAMBO Ammonium, Random, U 1842-4

Test Classification

This test has been modified from the manufacturer's instructions. Its performance characteristics were determined by Mayo Clinic in a manner consistent with CLIA requirements. This test has not been cleared or approved by the US Food and Drug Administration.

Forms

If not ordering electronically, complete, print, and send a Renal Diagnostics Test Request (T830) with the specimen.

Mayo Clinic Laboratories | Renal Diagnostics Catalog Additional Information:

mcl-neprolith, mcl-nephrolithiasis