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Stool Osmotic Gap Calculator (Eherer–Fordtran 1992)
x402
Stool Osmotic Gap Calculator (Eherer–Fordtran 1992) is a paid API for AI agents from api.magentlab.com, paid per call via x402, $0.005/call, status unknown (last checked 2026-09-15).
Computes the fecal osmotic gap using the Eherer–Fordtran 1992 formula: stool osmolality minus 2×(stool Na + stool K), defaulting stool osm to 290 mOsm/kg if not provided.
Price / call$0.005
Success—
StatusUnknown
How this service works
Eherer–Fordtran 1992 fecal osmotic gap: stool osmolality minus 2×(stool Na + stool K). Assumed stool osm 290 mOsm/kg when measured osm is omitted. Deterministic published arithmetic with citation; not a diagnosis of osmotic versus secretory diarrhea.
Output
Returns the computed fecal osmotic gap in mOsm/kg as a numeric value based on the Eherer–Fordtran 1992 formula (stool osmolality − 2 × [stool Na + stool K]), with stool osmolality defaulting to 290 mOsm/kg if not supplied. The result is a deterministic arithmetic output; it does not render a clinical diagnosis of osmotic vs. secretory diarrhea.
Example use cases
Diarrhea workup in hospital patient
“My patient has chronic watery diarrhea and the stool electrolytes came back: sodium 20 mmol/L, potassium 10 mmol/L. We didn't measure stool osmolality. What's the fecal osmotic gap?”
Using measured stool osmolality
“I have a full stool electrolyte panel: sodium 55 mmol/L, potassium 25 mmol/L, and measured osmolality of 310 mOsm/kg. Can you compute the osmotic gap using the Eherer–Fordtran formula?”
Automated GI report enrichment
“For this patient's stool report — Na 30 mmol/L, K 18 mmol/L, no osmolality recorded — calculate the fecal osmotic gap and include the result in the clinical summary.”
Technical details
Endpoint
GEThttps://api.magentlab.com/api/calc/stool_osmotic_gapWhen to prefer
Choose this endpoint when you need a fast, deterministic, citation-backed fecal osmotic gap calculation from stool electrolytes following the Eherer–Fordtran 1992 method. Ideal for clinical decision-support pipelines, automated lab report enrichment, or bedside GI workup tools where a reliable published formula is required. Prefer this over manual calculation when stool osmolality may be missing and the 290 mOsm/kg default assumption is acceptable.
Side effects
- Missing required stool_sodium_mmol_l or stool_potassium_mmol_l parameters returns a 400 error
- Values outside the accepted range (Na or K: 1–150 mmol/L; osm: 200–600 mOsm/kg) may be rejected or return an error
- Non-numeric inputs for any parameter will cause a validation failure
- Payment failure (402) if x402 USDC payment header is missing or rejected
Input
Schema · Request body
| Field | Type | Description |
|---|---|---|
| inputrequired | object | |
| output | object |
Output
Schema · Response
{
"type": "json",
"example": {
"path": "/api/calc/stool_osmotic_gap",
"count": 2,
"items": [
{
"formula": "eherer_fordtran",
"citation": {
"id": "eherer-fordtran-1992",
"doi": "10.1016/0016-5085(92)90845-P",
"title": "Fecal osmotic gap and pH in experimental diarrhea of various causes",
"source": "Gastroenterology. 1992;103(2):545-551",
"authors": "Eherer AJ, Fordtran JS"
},
"gap_gt_50": true,
"disclaimer": "Not a medical device. Deterministic published-formula or published-code output for autonomous agents. A licensed clinician remains responsible for patient care and billing submissions.",
"osmotic_gap": 80,
"stool_osm_mosm_kg": 290,
"assumed_osmolality": true,
"formula_expression": "osmotic_gap = stool_osm_mosm_kg - 2 * (stool_sodium_mmol_l + stool_potassium_mmol_l)",
"stool_sodium_mmol_l": 30,
"stool_potassium_mmol_l": 75
},
{
"formula": "eherer_fordtran",
"citation": {
"id": "eherer-fordtran-1992",
"doi": "10.1016/0016-5085(92)90845-P",
"title": "Fecal osmotic gap and pH in experimental diarrhea of various causes",
"source": "Gastroenterology. 1992;103(2):545-551",
"authors": "Eherer AJ, Fordtran JS"
},
"gap_gt_50": true,
"disclaimer": "Not a medical device. Deterministic published-formula or published-code output for autonomous agents. A licensed clinician remains responsible for patient care and billing submissions.",
"osmotic_gap": 80,
"stool_osm_mosm_kg": 290,
"assumed_osmolality": true,
"formula_expression": "osmotic_gap = stool_osm_mosm_kg - 2 * (stool_sodium_mmol_l + stool_potassium_mmol_l)",
"stool_sodium_mmol_l": 30,
"stool_potassium_mmol_l": 75
}
]
}
}Tags
x402
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