Phosphorus, Feces
Use
Useful in evaluating chronic diarrhea and identifying phosphate‑containing laxative use as a contributor to osmotic diarrhea. The concentration of electrolytes in fecal water depends on dietary intake, passive transport, and exogenous substances. Measurement of fecal phosphate helps distinguish osmotic from secretory diarrhea when elevated beyond 102 mg/dL suggests phosphate‑induced diarrhea. Osmotic diarrhea often results from poorly absorbed ions or sugars, while secretory diarrhea may stem from epithelial electrolyte transport disruption or infection. Phospholipids in liposomal drug formulations or rare gammopathies (e.g., IgM) may interfere with test accuracy.
Special Instructions
Ordering guidance indicates this test is only clinically valid on watery/fecal fluid specimens; formed stool will not be processed. No barium, laxatives, or enemas may be used for 96 hours before or during collection.
Limitations
Phospholipids in liposomal drug formulations (e.g., AmBisome) may hydrolyze and falsely elevate phosphate results. Rare gammopathies, particularly IgM (e.g., Waldenström macroglobulinemia), may produce unreliable results.
New York Approved
Methodology
Other
Biomarkers
LOINC Codes
- 88713-3
- 88713-3
Result Turnaround Time
1-3 days
Related Documents
For more information, please review the documents below
Specimen
Other
Volume
10 g
Minimum Volume
5 g
Container
Stool container
Collection Instructions
Collect a very liquid stool specimen.
Patient Preparation
No barium, laxatives, or enemas may be used for 96 hours prior to start of, or during, collection.
Causes for Rejection
Formed fecal specimens or preservatives added; specimens will be evaluated for suitability; formed specimens will not be performed.
Stability Requirements
| Temperature | Period |
|---|---|
| Room Temperature | 48 hours |
| Refrigerated | 7 days |
| Frozen | 14 days |