Reference Interval:
| Component
| Reference Interval
| | Sodium, Fecal
| Not Established
| | Potassium, Fecal
| Not Established
| | Magnesium, Fecal
| 0-110 mg/dL
| | Calculated Osmolality, Fecal
| By report
| | Osmolality, Fecal (measured)
| 0-16 years: 271-296 mOsm/kg
17 years and older: 280-303 mOsm/kg
| | Osmolal gap
| By report
| | | |
|
| Interpretive Data: |
Normal fecal fluid has an osmolality close to that of plasma (i.e., 290 mOsm/kg), a sodium concentration of about 30 mmol/L, a potassium concentration of about 75 mmol/L, and a magnesium concentration between 12 and 240 mg/dL (depending on diet) although it is usually less than 110 mg/dL. A fecal sodium greater than 90 mmol/L and an osmolal gap less than 50 mOsm/kg suggests secretory diarrhea or osmotic diarrhea due to sodium-containing laxatives. A fecal sodium less than 60 mmol/L and an osmolal gap greater than 100 mOsm/kg suggests osmotic diarrhea. Fecal sodium greater than 150 mmol/L and osmolality greater than 400 mOsm/kg suggests contamination with concentrated urine. Fecal osmolality less than 250 mOsm/kg suggests contamination with hypoosmotic urine or water.
|
| CPT Code(s): |
84999 Potassium; 84302 Sodium; 83735 Magnesium; 84999 Osmolality
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