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Potassium, Feces
Test Code14435
CPT Codes
84999
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.
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
Refrigerated: 7 days
Frozen: 60 days
Reject Criteria (Eg, hemolysis? Lipemia? Thaw/Other?)
Specimens in paint cans • Formed stool • Specimen received refrigerated
Methodology
Ion Selective Electrode (ISE)
Setup Schedule
Set up: Sun-Fri; Report available: 2-5 days
Reference Range
See Laboratory Report
Clinical Significance
This test measures potassium 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].
Stool potassium level is often measured in conjunction with stool sodium level to calculate osmotic gap, which is the difference between the stool osmolality and twice the sum of the stool sodium and potassium levels. Osmotic gap is useful in assessing the contribution of stool electrolytes to osmolality and differentiating between secretory and osmotic diarrhea [1,2].
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
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].
Stool potassium level is often measured in conjunction with stool sodium level to calculate osmotic gap, which is the difference between the stool osmolality and twice the sum of the stool sodium and potassium levels. Osmotic gap is useful in assessing the contribution of stool electrolytes to osmolality and differentiating between secretory and osmotic diarrhea [1,2].
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
