Test directory: Electrolyte & Osmolality Pnl, Fecal

Ordering Code 5778
Test Name Electrolyte & Osmolality Pnl, Fecal
Alias Electrolyte & Osmolality Profile,
Fecal
Preferred Specimen 24-hour or random liquid stool
Preferred Container Unpreserved stool transport vial
Optimum Volume 10 gm
Collection Instructions Do not combine with any other tests
Do NOT add saline or water to liquefy specimen.
Transport Requirements Oahu: Frozen
Airline: Frozen
Specimen Stability Ambient: Not Stable
Refrigerated: Not Stable
Frozen: 1 Month
Rejection Criteria Ambient, Refrigerated, Formed or viscous stools
Avail. Stat NO
Analytic Time Up to 7 Days
Methodology Quantitative Ion-Selective Electrode/Freezing Point
Reference Lab  ARUP Laboratories

Reference range(s)

The reference ranges listed below are valid on this date of June 1, 2025.
Component Age Male Norm Male Critical Low Male Critical High Female Norm Female Critical High Female Critical Low Units Add'l info
Sodium, Fecal ALL mmol/L
A reference... A reference interval has not been established for fecal specimens
Test developed and characteristics determined by ARUP Laboratories

See report.
Note1
Potassium, Fecal ALL mmol/L
A reference... A reference interval has not been established for fecal specimens
Test developed and characteristics determined by ARUP Laboratories

See report.
Note1
Magnesium, Fecal ALL 0-110 0-110 mg/dL
Calculated Osmolality ALL mOsm/kg See report.
Osmolality, Measured ALL mOsm/kg
0-16 years: 271... 0-16 years: 271-296 mOsm/kg 17 years and older: 280-303 mOsm/kg Access complete set of age- and/or gender-specific reference intervals for this test in the ARUP Laboratory Test Directory (aruplab.com)

See report.
Note2
Osmolal Gap ALL mOsm/kg
INTERPRETIVE... INTERPRETIVE INFORMATION: Normal fecal fluid has an osmolality close to that of plasma (i.e., 290 mOsm/kg), a sodium concentration of about 30 mmol/L, a potassium concentration of about 75 mmol/L, and a magnesium concentration between 12 to 240 mg/dL (depending on diet) although it is usually less than 110 mg/dL. A fecal sodium greater than 90 mmol/L and an osmolal gap less than 50 mOsm/kg suggest secretory diarrhea or osmotic diarrhea due to sodium-containing laxatives. A fecal sodium less than 60 mmol/L and an osmolal gap greater than 100 mOsm/kg suggest osmotic diarrhea. Fecal sodium greater than 150 mmol/L and osmolality greater than 400 mOsm/kg suggest contamination with concentrated urine. Fecal osmolality less than 250 mOsm/kg suggests contamination with hypoosmotic urine or water.
See report.
Note3

Note1:

A reference interval has not been established for fecal specimens
Test developed and characteristics determined by ARUP Laboratories

See report..

Note2:

0-16 years: 271-296 mOsm/kg 17 years and older: 280-303 mOsm/kg Access complete set of age- and/or gender-specific reference intervals for this test in the ARUP Laboratory Test Directory (aruplab.com)

See report..

Note3:

INTERPRETIVE INFORMATION: Normal fecal fluid has an osmolality close to that of plasma (i.e., 290 mOsm/kg), a sodium concentration of about 30 mmol/L, a potassium concentration of about 75 mmol/L, and a magnesium concentration between 12 to 240 mg/dL (depending on diet) although it is usually less than 110 mg/dL. A fecal sodium greater than 90 mmol/L and an osmolal gap less than 50 mOsm/kg suggest secretory diarrhea or osmotic diarrhea due to sodium-containing laxatives. A fecal sodium less than 60 mmol/L and an osmolal gap greater than 100 mOsm/kg suggest osmotic diarrhea. Fecal sodium greater than 150 mmol/L and osmolality greater than 400 mOsm/kg suggest contamination with concentrated urine. Fecal osmolality less than 250 mOsm/kg suggests contamination with hypoosmotic urine or water.
See report..