Liver & GIT
Secretory Diarrhea is caused by all of the following Except: (LQ)
|C||Excess phenolphthalein intake|
Chronic Diarrhea-Most cases are due to non-infectious causes.
The main etiology are-
I. Secretory-These are due to derangement in fluid and electrolyte transport across the enterocolic mucosa. They are characterized clinically by-
a. Watery, large volume, painless stools.
b. Diarrhea persists with fasting.
c. No fecal osmotic gap.
The important causes are-
1. Stimulant laxatives-senna, castor oil, bisacodyl
2. Chronic alcohol ingestion-due to enterocyte injury with impaired sodium and water absorption and rapid transit time.
a. Carcinoid-due to release of intestinal secretagogues like serotonin, histamine, prostaglandin.
b. Gastrinoma-due to marked volume overload to the small bowel, pancreatic enzyme inactivation by acid and damage of the intestinal epithelial surface by acid.
c. VIPoma-due to vasoactive intestinal peptide.
d. Medullary carcinoma of thyroid-due to calcitonin.
e. Systemic mastocytosis-due to histamine release and intestinal filtration by mast cells.
f. Colorectal villous adenoma-due to prostaglandin.
4. Congenital defect in ion absorption-due to defective Cl/HCO3 exchange(congenital chloridorrhea) and defective Na/H exchange.
5. Partial bowel obstruction-due to hypersecretion proximal to the obstruction site.
6. Bowel resection/enterocolic fistula-due to inadequate surface for resorption of secreted fluids and electrolytes. Diarrhea worsen with eating.
7. Bile acids-due to stimulation of colonic secretion.
8. Addison’s disease
II. Osmotic-Itoccurs due to osmotic active solute in the lumen which draw fluid in the lumen. Clinically these diarrhea stop with fasting. There is stool osmotic gap:290 -2 (Na+K) mosm/kg. The main causes are
a. Osmotic laxatives-containing magnesium, phosphorus, sulfate.
b. Lactase deficiency-due to osmotic active lactose.
c. Non absorbable carbohydrates-sorbitol, lactulose.
III. Steatorrhea-It is due to fat malabsorption with fecal fat excretion >6%. Clinically characterised by greasy, foul smelling and difficult to flush diarrhea.
The main causes are-
1. Intraluminal maldigestion-
i. Pancreatic insufficiency-When 90% of pancreatic secretory functions are lost.
ii. Bacterial overgrowth syndrome-due to de conjugation of bile acids by the bacteria and altered micelle formation.
iii. Liver disease-cirrhosis and biliary obstruction causing deficient intraluminal bile acid concentration.
2. Mucosal malabsorption-
i. Celiac sprue ii. Tropical sprue iii. Whipple’s disease iv. Giardia
Colchicine(inhibits crypt cell division and disaccharidase),
Cholestyramine (binds bile salts), Neomycin (reduce crypt cell division, precipitates bile salts and micellar fatty acids, inhibits disaccharidases).
vi. Abetalipoproteinemia-due to impaired chylomicron formation.
3. Post mucosal lymphatic obstruction-due to
i. Congenital intestinal lymphangiectasia
ii. Acquired lymphatic obstruction-due to trauma, tumor, infection.
The diarrhea is due to exudation, fat malabsorption, disruption of fluid and electrolyte absorption, hypersecreting / hypermotility due to cytokines. Clinically it is characterised by pain, fever and bleeding. The important causes are-
1. Inflammatory bowel diseases. 2. Collagenous colitis.
3. Eosinophilic gastroenteritis. 4. Immunodeficiency.
5. Radiation enterocolitis. 6. Chronic graft vs host reaction.
7. Beh|et’s syndrome.
It is due to rapid transit time. The main causes are
1. Hyperthyroidism-due to hyperphagia and rapid transit
2. Diabetes-due to pancreatic insufficiency, autonomic neuropathy, bacterial overgrowth, rapid transit time.
3. Visceral neuromyopathy
1. Munchausen syndrome