Test ID: KFT
Potassium, 24 Hour, Feces
Secondary ID 
A test code used for billing and in test definitions created prior to November 2011
NY State Approved Indicates the status of NY State approval and if the test is orderable for NY State clients.
Useful For Suggests clinical disorders or settings where the test may be helpful
Work-up of a patient with chronic diarrhea
Special Instructions and Forms Describes specimen collection and preparation information, test algorithms, and other information pertinent to test. Also includes pertinent information and consent forms to be used when requesting a particular test
Method Name A short description of the method used to perform the test
Inductively Coupled Plasma-Optical Emission Spectrometry (ICP-OES)
Reporting Name A shorter/abbreviated version of the Published Name for a test; an abbreviated test name
Aliases Lists additional common names for a test, as an aid in searching
Lytes
Potassium (K)
Electrolytes, Feces
Specimen Type Describes the specimen type needed for testing
Specimen Required Defines the optimal specimen. This field describes the type of specimen required to perform the test and the preferred volume to complete testing. The volume allows automated processing, fastest throughput and, when indicated, repeat or reflex testing.
Container/Tube: Stool container (Supply T291)
Specimen Volume: 20 g
Collection Instructions:
1. Collect a very liquid stool specimen.
2. See Stool Collection Information Sheet in Special Instructions.
Additional Information:
1. Do not send formed stool. In the event a formed stool is submitted, the test will not be performed. The report will indicate "A formed stool specimen was submitted for analysis. This test was not performed because it only has clinical value if performed on a watery stool specimen."
2. High concentrations of gadolinium and iodine are known to interfere with most metals tests. If either gadolinium- or iodine-containing contrast media has been administered, a specimen must not be collected for 96 hours.
Specimen Minimum Volume Defines the amount of specimen required to perform an assay once, including instrument and container dead space. Submitting the minimum specimen volume makes it impossible to repeat the test or perform confirmatory or perform reflex testing. In some situations, a minimum specimen volume may result in a QNS (quantity not sufficient) result, requiring a second specimen to be collected.
Reject Due To Identifies specimen types and conditions that may cause the specimen to be rejected
| Hemolysis | NA |
| Lipemia | NA |
| Icterus | NA |
| Other | Formed stool |
Specimen Stability Information Provides a description of the temperatures required to transport a specimen to the laboratory. Alternate acceptable temperature(s) are also included.
| Specimen Type | Temperature | Time |
|---|---|---|
| Fecal | Frozen (preferred) | 14 days |
| Refrigerated | 14 days | |
| Ambient | 7 days |
Clinical Information Discusses physiology, pathophysiology, and general clinical aspects, as they relate to a laboratory test
Potassium is an intracellular cation normally present in fecal water at a concentration approximately 20 times higher than the serum concentration.
The fecal water potassium content is comprised of 2 fractions-approximately 15% of the normal dietary intake of potassium (80 mEq/day) passes through the gastrointestinal (GI) tract to be deposited directly in fecal water, and a small fraction of potassium crosses the epithelial barrier of the GI tract from extra cellular fluids based on osmotic pressure.
In adults, the median daily excretion of potassium is 9 mEq/day, ranging from 0 mEq/day to 30 mEq/day. The median concentration of potassium in fecal water is 40 mEq/kg, ranging from 0 mEq/day to 200 mEq/kg. Potassium excretion is race-related; excretion in blacks is less than in Caucasians, usually by a factor of 2.
The fecal water potassium concentration and daily excretion rate will be normal if the cause of diarrhea is bacteria or due to ingestion of osmotic agents such as magnesium, phenolphthalein, and sulfate. The fecal water potassium daily excretion rate will be normal, but the measured concentration will be increased in patients with contracted colon volume.
Both the daily excretion rate of potassium and potassium concentration will be elevated in ulcerative colitis or other diseases where there is bleeding into the GI tract, exposure to cholera toxin, and in patients with islet cell tumors, increased secretion of vasointestinal peptide (vipoma syndrome), primary aldosteronism, ingestion of mineralocorticoids, and due to bacterial metabolism of unabsorbed carbohydrates passing through the GI tract.
Reference Values Describes reference intervals and additional information for interpretation of test results. May include intervals based on age and sex when appropriate. Intervals are Mayo-derived, unless otherwise designated. If an interpretive report is provided, the reference value field will state this.
0-15 years: not established
> or =16 years: 0-29 mEq/24 hour
Interpretation Provides information to assist in interpretation of the test results
Typically, stool potassium is 20 times serum potassium. A useful formula is 2x (stool sodium + stool potassium) = stool osmolality + or - 30 mOsm.
Fecal potassium concentration and daily excretion rate are usually below the median level in patients with osmotic diarrhea. Normal fecal sodium and potassium in the presence of an osmotic gap (>30 mOsm/kg) suggests osmotic diarrhea.
Increased fecal sodium content or daily excretion rate with normal fecal potassium and no osmotic gap indicates secretory diarrhea.
High fecal potassium in association with normal or low fecal sodium suggests deterioration of the epithelial membrane or a bleeding lesion
High sodium and potassium (3 times normal) in the absence of an osmotic gap indicate active electrolyte transport in the gastrointestinal tract that might be induced by agents such as cholera toxin, hypersecretion of vasointestinal peptide, or islet cell tumor.
For very low stool osmolality, consider factitial diarrhea.
The fecal potassium concentration and excretion rate are increased 2-fold to 3-fold with ulcerative colitis, or bleeding into the GI tract, when exposed to cholera toxin, with ingestion of mineralocorticoids, in primary aldosteronism, and due to bacterial metabolism of unabsorbed carbohydrates.
The fecal water potassium concentration and daily excretion rate exceeds 3 times normal in association with islet cell tumors and increased secretion of vasointestinal peptide.
Cautions Discusses conditions that may cause diagnostic confusion, including improper specimen collection and handling, inappropriate test selection, and interfering substances
This test will be performed on watery stools (diarrhea) only.
In the event a formed stool is submitted, the test will not be performed, and the report will indicate: "A formed stool specimen was submitted for analysis. This test was not performed because it only has clinical value if performed on a naturally occurring watery stool specimen."
High concentrations of gadolinium and iodine are known to interfere with most metals tests. If either gadolinium- or iodine-containing contrast media has been administered, a specimen must not be collected for 96 hours.
Clinical Reference Provides recommendations for further in-depth reading of a clinical nature
1. Phillips S, Donaldson L, Geisler K: Stool composition in factitial diarrhea: a 6-year experience with stool analysis. Ann Intern Med 1995;123:97-100
2. Agarwal R, Afzalpurkar R, Fordtran JS: Pathophysiology of potassium absorption and secretion by the human intestine. Gastroenterology 1994;107:548-571
3. Ho J, Moyer T, Phillips S: Chronic diarrhea: the role of magnesium. Mayo Clin Proc 1995;70:1091-1092
Method Description Describes how the test is performed and provides a method-specific reference
A small fraction of weighed feces is digested in hydrochloric acid and then analyzed for potassium concentration (along with magnesium and sodium) by inductively coupled plasma-optical emission spectroscopy (ICP-OES). Aqueous acidic calibrating standards, quality control samples, patient specimens, and blanks are diluted with diluent containing an internal standard. In turn, all diluted blanks, calibrating standards, quality control samples, and patient specimens are aspirated into a pneumatic nebulizer and the resulting aerosol directed to the hot plasma discharge by a flow of argon. In the annular plasma the aerosol is vaporized, atomized, and then ionized. Emission signals from potassium and the internal standard are observed radially by the emission spectrometer. Instrumentation response is defined by the linear relationship of analyte concentrations versus the ratio of the potassium emission signals ratioed with the internal standard. After reagent blank subtraction, unknown sample potassium concentrations are calculated by entering the net unknown intensity ratios into the linear calibration equation. (Unpublished Mayo method)
Day(s) and Time(s) Test Performed Outlines the days and times the test is performed. This field reflects the day and time the sample must be in the testing laboratory to begin the testing process and includes any specimen preparation and processing time required before the test is performed. Some tests are listed as continuously performed, which means assays are performed several times during the day.
Monday through Friday; evening
Analytic Time Defines the amount of time it takes the laboratory to setup and perform the test. This is defined in number of days. The shortest interval of time expressed is "same day/1 day," which means the results may be available the same day that the sample is received in the testing laboratory. One day means results are available 1 day after the sample is received in the laboratory.
Maximum Laboratory Time Defines the maximum time from specimen receipt at Mayo Medical Laboratories until the release of the test result
Specimen Retention Time Outlines the length of time after testing that a specimen is kept in the laboratory before it is discarded
Performing Laboratory Location The location of the laboratory that performs the test
Test Classification Provides information regarding the medical device classification for laboratory test kits and reagents. Tests may be classified as cleared or approved by the US Food and Drug Administration (FDA) and used per manufacturer's instructions, or as products that do not undergo full FDA review and approval, and are then labeled as an Analyte Specific Reagent (ASR), Investigation Use Only (IUO) product, or a Research Use Only (RUO) product.
CPT Code Information Provides guidance in determining the appropriate Current Procedural Terminology (CPT) code(s) information for each test or profile. The listed CPT codes reflect Mayo Medical Laboratories interpretation of CPT coding requirements. It is the responsibility of each laboratory to determine correct CPT codes to use for billing.
84999 (see CPT Coding in Special Instructions)
LOINC® Code Information Provides guidance in determining the Logical Observation Identifiers Names and Codes (LOINC) values for the result codes returned for this test or profile.
| Result ID | Reporting Name | LOINC Code |
|---|---|---|
| 60031 | Potassium, 24 Hr, F | 6792-6 |
| 2592 | Total Weight | 34648-6 |
| TM104 | Collection Duration | 13363-7 |
| 448 | Potassium Concentration | 25506-7 |
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