How is the fecal osmotic gap calculated? Fecal osmotic gap represents the osmotic activity in stool water not due to electrolytes. The sum of the concentrations of sodium and potassium in stool water is multiplied by 2 to account for the anions that are also present and this product is subtracted from 290 mOsm/kg, the approximate osmolality …
How secretory and osmotic watery diarrhea distinguished? The most useful way to differentiate secretory and osmotic types of watery diarrhea is to measure fecal electrolytes and calculate the fecal osmotic gap. In many diarrheal conditions, sodium and potassium along with their accompanying anions are the dominant electrolytes in stool water. In secretory diarrhea, there is …
The initial diagnostic scheme for patients with chronic diarrhea The scheme in the below image is based on obtaining a careful history, looking for specific physical findings, and obtaining simple laboratory data to help classify the diarrhea as watery, fatty, or inflammatory. The value of obtaining a quantitative (as opposed to a spot) stool collection is …
Likely causes of fatty diarrhea Malabsorption Syndromes Mucosal disease (celiac disease, Whipple disease) Small bowel bacterial overgrowth Chronic mesenteric ischemia Short bowel syndrome Postgastrectomy syndrome Maldigestion Pancreatic exocrine insufficiency Orlistat ingestion Inadequate luminal bile acid concentration
likely causes of inflammatory diarrhea Inflammatory bowel disease (ulcerative colitis, Crohn’s disease, diverticulitis, ulcerative jejunoileitis) Infectious diseases (pseudomembranous colitis, invasive bacterial infections [tuberculosis, yersiniosis], ulcerating viral infections [cytomegalovirus, herpes simplex], invasive parasitic infections [amebiasis, strongyloides]) Ischemic colitis Radiation colitis Neoplasia (colon cancer, lymphoma)
Likely causes of secretory watery diarrhea Bacterial toxins Ileal bile acid malabsorption Inflammatory bowel disease (ulcerative colitis, Crohn’s disease, microscopic colitis [lymphocytic and collagenous colitis], diverticulitis) Vasculitis Drugs and poisons Stimulant laxative abuse Disordered motility or regulation (postvagotomy diarrhea, postsympathectomy diarrhea, diabetic autonomic neuropathy, amyloidosis, irritable bowel syndrome) Endocrine diarrhea (hyperthyroidism, Addison’s disease, gastrinoma, vasoactive …
Likely causes of diarrhea according to epidemiologic characteristics Traveler’s Diarrhea Bacterial infection (mostly acute) Protozoal infection (e.g., amebiasis, giardiasis) Tropical sprue Epidemics and Outbreaks Bacterial infection Viral infection (e.g., rotavirus) Protozoal infections (e.g., cryptosporidiosis) Brainerd’s diarrhea (epidemic idiopathic secretory diarrhea) Patients with AIDS Opportunistic infections (e.g., cryptosporidiosis, cytomegalovirus, herpes, Mycobacterium avium complex) Drug side effect Lymphoma Institutionalized …