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HelpTest Code MISC2MAYOAMMO Ammonium, 24 Hour, Urine
Useful For
Diagnosis of the cause of acidosis
Diagnosis and treatment of kidney stones
Special Instructions
Method Name
Enzymatic
Reporting Name
Ammonium, 24 Hr, USpecimen Type
UrineNecessary Information
24-Hour volume (in milliliters) is required.
Specimen Required
Supplies:
-Sarstedt 5 mL Aliquot Tube (T914)
-Diazolidinyl Urea (Germall) 5.0 mL (T822)
Container/Tube: Plastic vial
Specimen Volume: 4 mL
Collection Instructions:
1. Add 5 mL of diazolidinyl urea (Germall) as preservative at start of collection or refrigerate specimen during and after collection.
2. Collect urine for 24 hours.
3. Aliquot urine into plastic vial.
4. Specimens with pH >8 may indicate bacterial contamination and testing will be cancelled. Do not attempt to adjust pH as it will adversely affect results.
Additional Information: See Urine Preservatives-Collection and Transportation for 24-Hour Urine Specimens for multiple collections.
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 |
Reject Due To
All specimens will be evaluated at Mayo Clinic Laboratories for test suitability.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 suggest ongoing gastrointestinal losses. Such patients are at risk of uric acid and calcium oxalate stones.
-Low urine ammonium and high urine pH suggest 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
15-56 mmol/24 hour
Reference values have not been established for patients <18 years and >77 years of age.
Reference values apply to 24 hour collections.
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.
Method Description
Urine samples are diluted 1:100 with clinical laboratory reagent water using a liquid handler and then are analyzed on a Roche cobas.(Package insert: Roche NH3L kit. Roche Diagnostics; V10/2016)
Day(s) Performed
Monday through Sunday
Report Available
Same day/1 to 2 daysPerforming Laboratory
Mayo Clinic Laboratories in Rochester
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.CPT Code Information
82140
LOINC Code Information
| Test ID | Test Order Name | Order LOINC Value |
|---|---|---|
| AMMO | Ammonium, 24 Hr, U | 25308-8 |
| Result ID | Test Result Name | Result LOINC Value |
|---|---|---|
| AM24 | Ammonium, 24 Hr, U | 25308-8 |
| TM25 | Collection Duration | 13362-9 |
| VL91 | Urine Volume | 3167-4 |
Forms
If not ordering electronically, complete, print, and send a Renal Diagnostics Test Request (T830) with the specimen.