Small intestine & ampulla

Infectious disorders

Diarrhea & dysentery

Topic Completed: 1 August 2012

Minor changes: 11 September 2020

Copyright: 2003-2021,, Inc.

PubMed Search: Diarrhea and dysentery small bowel

Hanni Gulwani, M.B.B.S.
Page views in 2020: 808
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Cite this page: Gulwani H. Diarrhea & dysentery. website. Accessed December 6th, 2021.
Definition / general
  • Usual fluid input into intestines is 9 liters/day (oral intake - 2, saliva - 1, gastric - 2, pancreatic - 2, intestinal - 1, other - 1)
  • Most reabsorbed in small bowel and colon
  • Diarrhea: increase in stool mass, frequency or stool fluidity (3 or more loose stools/day, eMedicine: Diarrhea [Accessed 13 February 2018])
  • Dysentery: low volume, painful, bloody diarrhea
  • Exudative disease: purulent bloody stools, persists with fasting - due to bacteria (Salmonella, Shigella, Campylobacter), Entamoeba histolytica, idiopathic inflammatory bowel disease, typhlitis
  • Malabsorption: bulky stools, abates with fasting, due to defective intraluminal digestion, primary mucosal cell abnormalities, reduced small bowel surface area, lymphatic obstruction, Giardia lamblia

Secretory diarrhea:
  • > 500 ml of fluid stool per day, isotonic with plasma, persists during fasting
  • Infectious (viral damage to epithelium): rotavirus, Norwalk virus, enteric adenoviruses, calicivirus, astrovirus
  • Infectious (enterotoxin): Vibrio cholera, E. coli, Bacillus cereus, Clostridium perfringens
  • Neoplastic: tumor production of peptides, villous adenoma in distal colon
  • Excessive laxatives

Osmotic diarrhea:
  • Due to luminal solutes, abates with fasting, stool osmolality > electrolyte concentration by 50 mOsm
  • Associated with lactase deficiency, lactulose therapy, gut lavage, antacids, primary bile acid malabsorption

Deranged motility:
  • Improper gut neuromuscular function causes decreased transit time
  • Due to surgical resection of gut, irritable bowel syndrome (neural dysfunction), hyperthyroidism, diabetic neuropathy, carcinoid syndrome
  • Decreased motility due to small bowel diverticula, blind loop, bacterial overgrowth
  • 12,000 deaths/year from dehydration in developing countries - 50% of all deaths before age 5
  • Affects 40% of U.S. population - #2 in attack rates in U.S. after common cold
Microscopic (histologic) description
  • Patchy lesions with variable villus abnormality, rarely severe
  • Increased chronic and acute inflammatory infiltrate in epithelium and lamina propria
  • Small intestinal bacterial overgrowth: common cause of chronic diarrhea and malabsorption with either villous blunting or normal duodenal biopsy (Arch Pathol Lab Med 2010;134:264)
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