Units: US SI

Stool Osmolar/Osmotic Gap

Stool Na mEq/L
Stool K mEq/L
Stool Osm mOsm/kg
Stool Osmotic Gap mOsm/kg
>100 suggests osmotic diarrhea, < 100 suggests secretory diarrhea

Stool Osmolal Gap = Stool Osm - (2 * (Na + K) )

Causes of osmotic diarrhea include:

  • Bile salt deficiency
  • Pancreatic insufficiency
  • Celiac/Tropical Sprue
  • Whipple's Dz
  • Intestinal Lymphoma
  • Medications
  • Lactose Intolerance
  • Laxative abuse (depending on the type of laxative)

Causes of secretory diarrhea include:

  • Laxative abuse (depending on the type of laxative)
  • Hormonal, Endocrine Tumors

Equations

Scores