Electrolytes, Feces

Test Code

ELECS

Quest Code

31595

Alias/See Also

Stool Chloride
ELECS
Stool Electrolytes

CPT Codes
82438, 84302, 84311

Includes

Sodium, Feces
Potassium, Feces
Chloride, Feces

Preferred Specimen

10 mL random watery liquid fecal collected in a plastic screw-cap container, or 24-hour, 48-hour or 72-hour watery liquid fecal collected in a plastic screw-cap container

Minimum Volume

2 mL

Instructions

Submit a frozen specimen of watery liquid feces in a plastic screw-cap container. Keep feces refrigerated during collection and transport frozen. 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.

Note: Specimen must be shipped frozen to reduce the odor during shipping and to minimize the risk of the container rupturing due to gas accumulation.

This test only has clinical utility if performed on a watery fecal specimen.
Stable up to 3 freeze-thaw cycles

Transport Temperature

Frozen

Specimen Stability

Room temperature: Unacceptable
Refrigerated: 7 days
Frozen: 60 days

Reject Criteria (Eg, hemolysis? Lipemia? Thaw/Other?)

Specimens in paint cans • Formed stool • Specimens received refrigerated

Methodology
Coulometric Titration • Flame Photometric

Setup Schedule

Set up: Sun-Fri; Report available: 3-5 days

Reference Range

See Laboratory Report

Clinical Significance

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.

Performing Laboratory
Quest Diagnostics Nichols Institute
14225 Newbrook Drive
Chantilly, VA 20153

Last Updated: September 10, 2019

The CPT Codes provided in this document are based on AMA guidelines and are for informational purposes only. CPT coding is the sole responsibility of the billing party. Please direct any questions regarding coding to the payor being billed. Any Profile/panel component may be ordered separately. Reflex tests are performed at an additional charge.