ELECTROLYTE & OSMOLALITY PROFILE, FECES

Code
000.0000
Name
ELECTROLYTE & OSMOLALITY PROFILE, FECES
Category
None
Department
Send-Out
Start Date
Expiration Date
Synonyms
CPT Codes
84999 x 2, 84302, 83735
Site
SBMF
Reference Test
44526
ATLAS Test Code

Specimen Information

Type

Routine random or 24-hour feces collection

Sample must be liquid, test is not indicated for patients passing non-liquid feces

Transfer sample aliquot to plastic screw-top container. Freeze and transport frozen.

Volume

10.0 g

Transport Info

Transfer sample aliquot to plastic screw-top container. Freeze and transport frozen.

Fasting Required?
False
Patient Instructions

Reference Range

See report

Methodology

Ion-Selective Electrode, Freezing Point Depression

Clinical Significance

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 suggests 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 suggests osmotic diarrhea. Fecal sodium greater than 150 mmol/L and osmolality greater than 400 mOsm/kg suggests contamination with concentrated urine. Fecal osmolality less than 250 mOsm/kg suggests contamination with hypoosmotic urine or water.

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