Stephen J. Schueler, M.D.

Diarrhea Underlying Cause

Muscles in the intestinal wall push the food through the intestine. Normally, the body absorbs nutrients and water from the food as it passes through the intestine. Diarrhea occurs when the amount of fluid in the stool increases.

The amount of fluid in the stool can increase by three mechanisms:

  • The intestine becomes irritated or swollen, which causes water, mucus or blood to leak from the wall of the intestine.
  • The muscles push food through the intestine too quickly. The intestine does not have enough time to remove the fluid from the digested food.
  • The digested food acts as a sponge, drawing extra water from the intestine, into the stool.

Causes of diarrhea are separated into two groups:
  • Infections that cause diarrhea
  • Other illnesses that cause diarrhea

Diarrhea Infectious

Organisms that cause diarrhea invade the wall of the intestine or produce toxins. The infection causes swelling and irritation of the lining to the intestine. These infections spread through contaminated food or water.

Infectious causes for diarrhea include:

Diarrhea Non-Infectious

Last Updated: Dec 19, 2006 References
Authors: Stephen J. Schueler, MD; John H. Beckett, MD; D. Scott Gettings, MD
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PubMed Diarrhea References
  1. Aranda-Michel J, Giannella RA. Acute diarrhea: a practical review. Am J Med. 1999 Jun;106(6):670-6. [10378626]
  2. Camilleri M. Chronic diarrhea: a review on pathophysiology and management for the clinical gastroenterologist. Clin Gastroenterol Hepatol. 2004 Mar;2(3):198-206. [15017602]
  3. Fine KD, Schiller LR. AGA technical review on the evaluation and management of chronic diarrhea. Gastroenterology. 1999 Jun;116(6):1464-86. [10348832]
  4. Mylonakis E, Ryan ET, Calderwood SB. Clostridium difficile--Associated diarrhea: A review. Arch Intern Med. 2001 Feb 26;161(4):525-33. [11252111]
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