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Epic Code LAB1231976 Electrolytes, Feces

Test Name Alias

LAB1230027 | Electrolytes | Quest: 31595

Interface Order Alias

1231992

Clinical Information

Includes

  • Sodium, Feces
  • Potassium, Feces
  • Chloride, Feces

Electrolytes, Feces -

This panel measures sodium, potassium, and chloride in liquid stool. Measurements of electrolytes and osmotic gap in liquid stool help differentiate between secretory and osmotic diarrhea and, thus, guide further evaluation of chronic diarrhea [1,2].

Diarrhea can be categorized as secretory or osmotic depending on how the water content of stool is drawn in the intestine lumen. Secretory diarrhea is caused by defective electrolyte absorption that increases the stool's electrolyte levels. Conditions associated with secretory diarrhea include infection, neuroendocrine tumors, congenital chloridorrhea, intestinal resection, and diffuse mucosal disease [1]. Osmotic diarrhea is caused by the osmotic effect of a substance that retains water in the intestine lumen and leads to decreased electrolyte levels in the stool. Conditions associated with osmotic diarrhea include ingesting poorly absorbed solutes (eg, sorbitol, mannitol, and laxatives containing magnesium) and enzyme dysfunction (eg, lactose intolerance) [2].

Osmotic gap, calculated as the difference between the stool osmolality and twice the sum of the stool sodium and potassium levels, is useful in assessing the contribution of stool electrolytes to osmolality and differentiating between secretory and osmotic diarrhea [1,2].A theoretical fecal osmolality, approximately the same as plasma osmolality (290 mOsm/kg), is used in the calculation.

Measurement of chloride in liquid stool aids in the diagnosis of congenital or secondary chloridorrhea, which is characterized by increased excretion of chloride in stool. Low levels of chloride in liquid stool may also be seen in sodium sulfate-induced diarrhea [2].

The results of this test should be interpreted in the context of pertinent clinical and family history and physical examination findings.

References
1. Schiller LR. Pract Res Clin Gastroenterol. 2012;26(5):551-562.
2. Block DR, et al. Body fluids. In: Rifai R, et al. eds. Tietz Textbook of Laboratory Medicine. 7th ed. Elsevier Inc; 2022.

Specimen Requirements

Specimen Collection Criteria

Collect: 24-hour, 48-hour or 72-hour or random liquid stool.

Only watery liquid feces are an acceptable specimen. In the event a formed fecal specimen is submitted, the test will not be performed and will be cancelled.

  • 24-hour, 48-hour or 72-hour Collection:  Keep feces refrigerated during collection

 

. Collect using the Kit, Fecal Fat, Stool. Please call for this kit.

  • Random: 10 mL random watery liquid fecal collected in a plastic screw-cap container

 

Physician Office/Draw Specimen Preparation

Refrigerate (2-8°C or 36-46°F) the specimen immediately after collection. Freeze (-20°C/-4°F or below) specimens that will not be received in the Laboratory within two hours of collection.

 

In-Lab Processing

The specimen should be frozen (-20°C/-4°F or below) if not analyzed within two hours of collection.

24-hour, 48-hour or 72-hour Collection: Transport the entire collection in the original collection kit. (Minimum: 5 g) Do not add saline or water to liquefy specimen. Indicate time and volume.

Random Collection: Transfer 10 mL stool to unpreserved stool transport vial. (Minimum: 2 mL) Do not add saline or water to liquefy specimen. Indicate time and volume.

CRITICAL FROZEN. Separate specimens must be submitted when multiple tests are ordered.

Specimen Transport Temperature

Transport: Stool specimen refrigerated (2-8°C or 36-46°F) or frozen (-20°C/-4°F or below).

Rejection Criteria

  • Formed (solid) stool specimens.
  • Specimens not collected and processed as indicated.

Specimen Stability

Specimen Stability for Testing:
Room Temperature (20-26°C or 68-78.8°F): Unacceptable
Refrigerated (2-8°C or 36-46°F): 7 days
Frozen (-20°C/-4°F or below): 1 month


Specimen Storage in Department Prior to Disposal:
Specimen retention time is determined by the policy of the reference laboratory. Contact the Send Outs Laboratory with any questions.

Test Frequency

Information not provided.

Reference Range

By report.

Performing Department

Send Outs

Performing Department Laboratory Location

Sent to Quest Diagnostics Nichols Institute-Chantilly VA

Methodology

Coulometric Titration • Flame Photometric

CPT

82438, 84302, 84311

LOINC

Unavailable

Reviewed Date

11/8/2025

Orderable Regions

Send Outs