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Test Code LAB201 Osmolality, Feces

Additional Codes

OSMOF


Ordering Guidance


This test is only clinically valid if performed on watery specimens. In the event a formed fecal specimen is submitted, the test will not be performed.



Specimen Required


Patient Preparation: No barium, laxatives, or enemas may be used for 96 hours prior to start of, or during, collection.

Supplies: Stool containers - 24, 48, 72 Hour Kit (T291)

Container/Tube: Stool container

Specimen Volume: 10 g

Collection Instructions: Collect a very liquid stool specimen.


Secondary ID

606758

Useful For

Measurement of osmolality for the workup of cases of chronic diarrhea

 

Diagnosis of factitious diarrhea (where patient adds fluid to stool to simulate diarrhea)

Method Name

Freezing Point Depression

Specimen Type

Fecal

Specimen Minimum Volume

5 g

Specimen Stability Information

Specimen Type Temperature Time Special Container
Fecal Frozen (preferred) 14 days
  Refrigerated  7 days
  Ambient  48 hours
Medical University of South Carolina Note:

On-campus collections: Tube to 99 or deliver to University Extension Hospital Room EH318
Send in plastic container, Frozen.
 
Off-campus collections: 
Specimen to be stored/transported at Frozen temp. 
 

Reject Due To

All specimens will be evaluated at Mayo Clinic Laboratories for test suitability.

Reference Values

An interpretive report will be provided

Interpretation

Stool osmolality below 220 mOsm/kg indicates dilution with a hypotonic fluid.(1)

Method Description

The depression of the freezing point of serum or other fluid is used to measure osmolality in most osmometers. The extent of lowering below 0° C (the freezing point of water) is a function of the concentration of substances dissolved in the serum. By definition, 1 milliosmole per kilogram lowers the freezing point 0.001858° C.(Schnidler EI, Brown SM, Scott MG: Electrolytes and Blood Gases. In: Rifai N, Horvath AR, Wittwer CT, eds: Tietz Textbook of Clinical Chemistry and Molecular Diagnostics. 6th ed. Elsevier; 2018:610-612)

Specimen Retention Time

7 days

Performing Laboratory

Mayo Clinic Laboratories in Rochester

CPT Code Information

84999

LOINC Code Information

Test ID Test Order Name Order LOINC Value
OSMOF Osmolality, F 2693-0

 

Result ID Test Result Name Result LOINC Value
OSMOF Osmolality, F 2693-0

Day(s) Performed

Monday, Thursday

Report Available

1 to 3 days