What is diarrhea?

Diarrhea refers to a familiar phenomenon with unusually frequent or liquid bowel movements, excessive watery evacuations of fecal material. Diarrhea is the opposite of constipation.

The word “diarrhea” with its odd spelling is a near steal from the Greek “diarrhoia” meaning “a flowing through.” (Plato and Aristotle may have had diarrhoia while today we have diarrhea.)

What are the causes of diarrhea?

There are many causes of diarrhea which can be divided into two major categories — infectious and noninfectious. Infectious causes of diarrhea are a result of abnormal microorganisms invading the bowels. Noninfectious causes of diarrhea are not due to microorganisms, but result from disturbances of the normal function of the bowel in absorbing fluids contained within it.

Infectious causes of diarrhea can be subdivided, according to the type of microorganism involved as follows:

  • Bacteria
  • Viruses
  • Parasites

The bacteria capable of causing diarrhea include by way of examples:

  • Clostridrium difficile
  • Escherichia coli (better known as E. coli)
  • Salmonella (the agents of typhoid fever and many other diseases including much Gastroenteritis and enteric fever from contaminated food products)
  • Shigella (a cause of epidemic bacillary dysentery)
  • Campylobacter (another food-handler’s contaminant)
  • Vibrio cholerae (the agent of cholera)

There are many kinds of viruses that can cause diarrhea and they are common in our everyday lives. During their first 5 years of life, all children acquire rotavirus (which causes inflammation of the stomach and bowels to cause diarrhea) and almost all children acquire other viruses causing intestinal disease.

There is also a variety of parasites that produce diarrhea. Among them are such notorious agents as:

  • Cryptosporidium (a major cause of diarrhea in immunodeficient persons)
  • Entamoeba histolytica (which causes amebic dysentery)
  • Giardia lamblia

Giardia has a large sucking disk by which it holds onto the inside of the intestine, prevents food from being absorbed there. This causes malabsorption of fluids in the bowels and speeds contents through the intestines to produce diarrhea. By age 5, many children have acquired Giardia.

Noninfectious causes of diarrhea can be categorized as follows:

  • Anatomy defects of the bowels (intestinal tract)
  • Hormonal imbalances (endocrinopathies)
  • Feeding difficulties
  • Food poisoning
  • Malabsorption
  • Tumors
  • Miscellaneous causes

The anatomic defects of the intestinal tract capable of causing diarrhea include:

  • Malrotation of the bowel (when it is twisted)
  • Duplication of a section of the intestine
  • Hirschsprung disease

Hirschsprung’s disease is an abnormal condition present at birth which is due to absence of the normal nerves (ganglia) in the bowel wall. Nerves can be missing in this condition starting at the anus and extending up a variable distance of the bowel. This results in enlargement of the bowel above the point of missing nerves. (The nerves normally assist in the natural movement of the muscles in the lining of our bowels which move bowel contents through.) Hirschsprung disease (also known as congenital aganglionic megacolon) is the commonest cause of lower intestinal blockage (obstruction) in the newborn and later a cause of chronic constipation or, paradoxically, chronic diarrhea.