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Test ID: NITU Nitrogen, Total, 24 Hour, Urine

Reporting Name

Nitrogen, Total, U

Useful For

Assessing nutritional status (protein malnutrition)

 

Assessment of protein nutrition and nitrogen balance in hospitalized patients

 

Evaluating protein catabolism

 

Determining nitrogen balance, when used in conjunction with 24-hour fecal nitrogen measurement

Clinical Information

Nitrogen is a key component of proteins. Nitrogen balance is the difference between the amount of nitrogen ingested and the amount excreted in the urine and feces. A majority of nitrogen is excreted as urea in the urine; however, fecal nitrogen can account for 30% to 50% of total nitrogen excretion.

 

A patient who is in negative nitrogen balance is catabolizing muscle protein to meet the metabolic requirements of the protein catabolism and, therefore, urine and fecal nitrogen may be increased due to stress, physical trauma, surgery, infections, burns, and 11-oxysteroid or thyroxine use. Testosterone and growth hormone have anabolic effects on protein synthesis and may decrease urine and fecal nitrogen.

 

In the course of chronic progressive pancreatitis, as the pancreas is destroyed, serum amylase and lipase may revert to normal. However, excessive fecal nitrogen levels persist and are used as an indicator of pancreatic atrophy.

Interpretation

Urinary nitrogen excretion levels within the normal range are indicative of adequate nutrition. Slightly abnormal excretion rates may be a result of moderate stress or complications such as infection or trauma. Significantly abnormal excretion rates may be associated with severe stress due to multiple trauma, head injury, sepsis, or extensive burns. The goal with therapy for a depleted person is a positive nitrogen balance of 4 to 6 g nitrogen/24 hours.

Analytic Time

1 day

Day(s) and Time(s) Performed

Friday; 8 a.m.

Clinical Reference

1. Morse MH, Haub MD, Evans WJ, Campbell WW: Protein requirement of elderly women: nitrogen balance responses to three levels of protein intake. J Gerontol A Biol Sci Med Sci. 2001 Nov;56(11):M724-730

2. Phinney SD: The assessment of protein nutrition in the hospitalized patient. Clin Lab Med. 1981;1:767-774

3. Konstantinides FN, Kostantinides NN, Li JC, Myaya ME, Cerra FB: Urinary urea nitrogen: too insensitive for calculating nitrogen balance studies in surgical clinical nutrition. J Parenter Enteral Nutr. 1991 Mar-Apr;15:189-193

4. Borowitz D, Konstan MW, O'Rourke A, et al: Coefficients of fat and nitrogen absorption in healthy subjects and individuals with cystic fibrosis. J Pediatr Pharmacol Ther.. 2007 Jan;12(1):47-52. doi: 10.5863/1551-6776-12.1.47

Method Name

Dumas Combustion

Specimen Type

Urine


Necessary Information


24-Hour volume is required.



Specimen Required


Supplies: Urine Tubes, 10 mL (T068)

Container/Tube: Plastic, 10-mL urine tube

Specimen Volume: 10 mL

Collection Instructions:

1. Collect urine for 24 hours.

2. No preservative. Refrigerated is the preferred preservation method.

Additional Information: See Urine Preservatives-Collection and Transportation for 24-Hour Urine Specimens in Special Instructions for multiple collections.


Specimen Minimum Volume

2 mL

Specimen Stability Information

Specimen Type Temperature Time Special Container
Urine Refrigerated (preferred) 7 days
  Ambient  7 days
  Frozen 

Reference Values

<16 years: not established

≥16 years: 4-20 g/24 hours

Test Classification

This test was developed and its performance characteristics determined by Mayo Clinic in a manner consistent with CLIA requirements. This test has not been cleared or approved by the U.S. Food and Drug Administration.

CPT Code Information

84999

LOINC Code Information

Test ID Test Order Name Order LOINC Value
NITU Nitrogen, Total, U 2660-9

 

Result ID Test Result Name Result LOINC Value
17418 Nitrogen, Total, U 2660-9
DUR8 Collection Duration 13362-9
TOTV Specimen Volume 28009-9

Urine Preservative Collection Options

Note: The addition of preservative or application of temperature controls must occur within 4 hours of completion of the collection.

Ambient

OK

Refrigerate

Preferred

Frozen

OK

50% Acetic Acid

OK

Boric Acid

No

Diazolidinyl Urea

No

6M Hydrochloric Acid

OK

6M Nitric Acid

No

Sodium Carbonate

OK

Thymol

OK

Toluene

No

 

Mayo Clinic Laboratories | Endocrinology Catalog Additional Information:

mml-diabetes-metabolic-nutrition