Electrolyte and Osmolality Profile, Stool (Sendout)

General Information

Lab Name

Lab Code

RSLYTO

Epic Name

Electrolyte and Osmolality Profile, Stool (Sendout)

External Test Id

0020699

Description

Useful For: Measurement of electrolytes and osmolality in feces as part of a chronic diarrhea workup.

Ordering Note: This panel includes the following components: sodium, potassium, magnesium, osmolality (measured), calculated osmolality, and osmolal gap. Chloride and phosphorus are not included, but may be ordered separately. Refer to Chloride, Stool (Sendout) [RSCHLD] and Phosphorus, Stool (Sendout) [#1177]. The Electrolyte and Osmolality Profile (this test) and Chloride may be performed on the same stool sample. A separate sample is required for Phosphorus stool testing, as it is performed by a different reference lab.

Synonyms

0020699, Magnesium stool, Osmolal gap, Osmolality Stool, Osmotic gap, Potassium stool, SLYT, Sodium stool, Stool electrolytes, Stool osmotic gap

Components

Code	Name
RSLOIN	Collection Interval, Stool
RSLOFW	Total Weight, Stool
RSMAGV	Magnesium per volume, Stool
RSTLK	Potassium, Stool
RSTLNA	Sodium, Stool
RSOSMO	Osmolality Fecal (Measured), Stool
RSOSMC	Calculated Osmolality, Stool
RSOGAP	Osmolal Gap, Stool

Interpretation

Method

Quantitative Ion-Selective Electrode/Freezing Point

Reference Range

See individual components

Ref. Range Notes

Reference Interval:

Sodium, Stool:	Not Established
Potassium, Stool:	Not Established
Magnesium per volume, Stool:	0-110 mg/dL
Calculated Osmolality, Stool:	By report
Osmolality, Fecal (Measured), Stool:	0-16 years: 271-296 mOsm/kg 17 years and older: 280-303 mOsm/kg
Osmolal Gap, Stool:	By report

Interpretive Data: 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 and 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.

Ordering & Collection

Specimen Type: Stool
Collection: Collect 5 g random liquid stool in a preservative-free container.
Handling Instructions: Outside Laboratories: Freeze stool at -20°C while awaiting shipment. Transport on dry ice.

Stability: Frozen (preferred): 1 month; Refrigerated: 1 week; Ambient: Unacceptable.

Unacceptable Conditions: Formed or viscous stool. Specimens in media or preservative. Specimens that have had saline or water added to liquefy specimen.
Quantity: Requested: 5 g liquid stool
Minimum: 5 g liquid stool

Processing

Receiving Instructions

Freeze stool at -20°C.

Sendouts:

Order ARUP Test: 0020699
Interfaced: Yes [Interface: 602; Department: ARPZ]

Stability: Frozen (preferred): 1 month; Refrigerated: 1 week; Ambient: Unacceptable.

Unacceptable Conditions: Formed or viscous stool. Specimens in media or preservative. Specimens that have had saline or water added to liquefy specimen.

Misc Sendout

Performance

Lab Department

Sendouts ARUP Lab (FZ)(ARPZ)

Frequency

Performed: Sunday through Saturday. Reported: 1-2 days from sample receipt at ARUP Laboratories.

Available STAT?

Performing Location(s)

Sendout	ARUP Laboratories, Inc. 800-522-2787 500 Chipeta Way Salt Lake City, UT 84108

Billing & Coding

CPT Codes: 83735, 84302, 84999x2
LOINC: 88697-8
Interfaced Order Code: UOW5444