To most individuals, diarrhea means an increased frequency or decreased consistency of bowel movements; however, the medical definition is more exact than this. Diarrhea best correlates with an increase in stool weight; this increase is mainly due to excess water, which normally makes up 60 to 85 percent of fecal matter. In this way, true diarrhea is distinguished from diseases that cause only an increase in the number of bowel movements (hyperdefecation) or incontinence (involuntary loss of bowel contents).

Diarrhea is also classified by physicians as acute, which lasts one to two weeks, and as chronic, which continues for longer than two or three weeks. Viral and bacterial infections are the most common causes of acute diarrhea.


In many cases, acute infectious diarrhea is a mild, limited annoyance common to adults and children. Chronic diarrhea, though, can have considerable effect on health and on social and economic well-being. People with celiac disease , inflammatory bowel disease, and other prolonged diarrheal illnesses develop nutritional deficiencies that diminish growth and immunity. They affect social interaction and result in the loss of many working hours. Rapid diagnosis and proper treatment can prevent much of the suffering associated with these illnesses.


Worldwide, acute infectious diarrhea has a huge impact, causing over 5 million deaths per year. While most deaths are among children under five years of age in developing nations, the impact, even in developed countries, is considerable. For example, over 250,000 individuals are admitted to hospitals in the United States each year because of one of these episodes.

Causes and symptoms

Diarrhea occurs because more fluid passes through the large intestine (colon) than that organ can absorb. As a rule, the colon can absorb several times more fluid than is required on a daily basis. However, when this reserve capacity is overwhelmed, diarrhea occurs.

Diarrhea is caused by infections or illnesses that either lead to excess production of fluids or prevent absorption of fluids. Also, certain substances in the colon, such as fats and bile acids, can interfere with water absorption and cause diarrhea. Rapid passage of material through the colon can also do the same.

Symptoms related to any diarrheal illness are often those associated with any injury to the gastrointestinal tract, such as fever , nausea , vomiting , and abdominal pain . All or none of these may be present depending on the disease causing the diarrhea. The number of bowel movements can vary—up to 20 or more per day. In some persons, blood or pus is present in the stool. Bowel movements may be difficult to flush (float) or contain undigested food material.

The most common causes of acute diarrhea are infections (the cause of traveler's diarrhea), food poisoning , and medications. Medications are a frequent and often over-looked cause, especially antibiotics and antacids. Less often, various sugar-free foods, which sometimes contain poorly absorbable materials, cause diarrhea.

Chronic diarrhea is frequently due to many of the same things that cause the shorter episodes (infections, medications, etc.); however, symptoms last longer. Some infections can become chronic. This occurs mainly with parasitic infections (such as Giardia ) or when people have altered immunity (such as AIDS ). In children, more common causes of chronic diarrhea are food allergy and lactose intolerance . Toddlers who drink too much juice can have frequent, loose stools.

When to call the doctor

A physician or other healthcare provider should be contacted when the number of bowel movements exceeds three per day for 2 days or more or when fecal material contains blood. A doctor should be called if a person becomes dehydrated. Signs of dehydration include decreased urination, lethargy, poor skin tone, and generalized weakness. In very young children, the parents should call a doctor if they observe these symptoms of dehydration:

  • dry mouth or tongue
  • few or no tears when crying
  • no wet diapers for three hours or more
  • sunken eyes, cheeks, and fontanel (soft spot on the head of infants)
  • irritability and listlessness
  • skin that flattens slowly when pinched

Parents should also call the doctor if a child is vomiting so often that he or she cannot keep fluids down, has a high fever, complains of severe abdominal pain, or shows no improvement in symptoms after 24 hours.


Most cases of acute diarrhea never need diagnosis or treatment, as many are mild and produce few problems. But persons of any age with fever over 102°F (38.9°C), signs of dehydration, bloody bowel movements, severe abdominal pain, known immune disease, or prior use of antibiotics need prompt medical evaluation.

When diagnostic studies are needed, the most useful are stool culture and examination for parasites; however, these are often negative, and a cause cannot be found in a large number of people. The earlier cultures are performed, the greater the chance of obtaining a positive result. For those with a history of antibiotic use in the preceding two months, stool samples need to be examined for the toxins that cause antibiotic-associated colitis. Tests are also available to check stool samples for microscopic amounts of blood and for cells that indicate severe inflammation of the colon. Examination with an endoscope is sometimes helpful in determining severity and extent of inflammation. Tests to check changes in blood chemistry (potassium, magnesium, etc.) and a complete blood count (CBC) are also often performed.

Chronic diarrhea is quite different, and most persons with this condition receive some degree of testing. Many exams are the same as for an acute episode, as some infections and parasites cause both types of diarrhea. A careful history to evaluate medication use, dietary changes, family history of illnesses, and other symptoms is necessary. Key points in determining the seriousness of symptoms are weight loss of over 10 lbs (4.5 kg), blood in the stool, and nocturnal diarrhea (symptoms that awaken an individual from sleep ).

Both prescription and over-the-counter medications can contain additives, such as lactose and sorbitol, that will produce diarrhea in sensitive individuals. Review of allergies or skin changes may also point to a cause. Social history may indicate that stress is playing a role or may identify activities which can be associated with diarrhea (for example, diarrhea that occurs in runners).

A combination of stool, blood, and urine tests may be needed in the evaluation of chronic diarrhea; in addition, a number of endoscopic and x-ray studies are frequently required.


Treatment is ideally directed toward correcting the cause; however, the first aim should be to prevent or treat dehydration and nutritional deficiencies. The type of fluid and nutrient replacement depends on whether oral feedings can be taken and on the severity of fluid losses. Oral rehydration solution (ORS) or intravenous fluids are the choices; ORS is preferred if possible.

A physician should be notified if a person is dehydrated. If oral replacement is suggested then commercial (Pedialyte and others) or homemade preparations can be used. The World Health Organization (WHO) has provided this easy recipe for home preparation, which can be taken in small frequent sips:

  • table salt, 3/4 tsp
  • baking powder, 1 tsp
  • orange juice, 1 c
  • water, 1 qt

When feasible, food intake should be continued even in those people with acute diarrhea. A physician should be consulted regarding what type and how much food is permitted.

Anti-motility agents (loperamide, diphenoxylate) are useful for those with chronic symptoms; their use is limited or even contraindicated in most individuals with acute diarrhea, especially in those with high fever or bloody bowel movements. They should not be taken without the advice of a physician, and should not be used in children.

Other treatments are available, depending on the cause of symptoms. For example, the bulk agent psyllium helps some people by absorbing excess fluid and solidifying stools; cholestyramine, which binds bile acids, is effective in treating bile-salt-induced diarrhea. Low fat diets or more easily digestible fat is useful in some people. Antidiarrheal drugs that decrease excessive secretion of fluid by the intestinal tract is another approach for some diseases. Avoidance of medications or other products that are known to cause diarrhea (such as lactose) is curative in some people but should be discussed with a physician.

Alternative treatment

It is especially important to find the cause of diarrhea, since stopping diarrhea when it is the body's way of eliminating something foreign is not helpful and can be harmful in the long run.

One effective alternative approach to preventing and treating diarrhea involves oral supplementation of aspects of the normal flora in the colon with the yeasts Lactobacillus acidophilus , L. bifidus , or Saccharomyces boulardii . In clinical settings, these "biotherapeutic" agents have repeatedly been helpful in the resolution of diarrhea, especially antibiotic-associated diarrhea.

Nutrient replacement also plays a role in preventing and treating episodes of diarrhea. Zinc especially appears to have an effect on the immune system, and deficiency of this mineral can lead to chronic diarrhea. Also, zinc replacement improves growth in young persons. To prevent dehydration, individuals suffering from diarrhea should take plenty of fluids, especially water. The BRAT diet also can be useful in helping to resolve diarrhea. This diet limits food intake to bananas, rice, applesauce, and toast. These foods provide soluble and insoluble fiber without irritation. If the toast is slightly burnt, the charcoal can help sequester toxins and pull them from the body.

Acute homeopathic remedies can be very effective for treating diarrhea especially in infants and young children.


Prognosis is related to the cause of the diarrhea; for most individuals in developed countries, a bout of acute, infectious diarrhea is at best uncomfortable. However, in both industrialized and developing areas, serious complications and death can occur.

For those with chronic symptoms, an extensive number of tests are usually necessary to make a proper diagnosis and begin treatment; a specific diagnosis is found in 90 percent of people. In some, however, no specific cause is found and only treatment with bulk agents or anti-motility agents is indicated.


Proper hygiene and food handling techniques can prevent many cases. Traveler's diarrhea can be avoided by people using products containing bismuth, such as Pepto-Bismol and/or antibiotics. The most important action is to prevent the complications of dehydration.

Nutritional concerns

Replacement of fluids and electrolytes is important for people experiencing diarrhea. These individuals should take in foods that contain salt, potassium, phosphates, and sugar. Most sodas, sport drinks and non-cream soups are good sources of electrolytes.

Parental concerns

Parents should be sure that their children who experience diarrhea drink plenty of fluids and replace electrolytes with an oral rehydration solution. A doctor should be called if the parent suspects a child is becoming dehydrated. Severe dehydration requires intravenous fluid administration in a medical setting. Antidiarrheal medications should be be given only on the advise of a physician.


Antimotility drug —A medication, such as loperamide (Imodium), dephenoxylate (Lomotil), or medications containing codeine or narcotics that decrease the ability of the intestine to contract.

Colitis —Inflammation of the colon (large intestine).

Endoscope —A medical instrument that can be passed into an area of the body (the bladder or intestine, for example) to allow visual examination of that area. The endoscope usually has a fiberoptic camera that allows a greatly magnified image to be shown on a television screen viewed by the operator. Many endoscopes also allow the operator to retrieve a small sample (biopsy) of the area being examined, to more closely view the tissue under a microscope.

Endoscopy —Visual examination of an organ or body cavity using an endoscope, a thin, tubular instrument containing a camera and light source. Many endoscopes also allow the retrieval of a small sample (biopsy) of the area being examined, in order to more closely view the tissue under a microscope.

Lactose intolerance —An inability to properly digest the lactose found in milk and dairy products.

Oral rehydration solution (ORS) —A liquid preparation of electrolytes and glucose developed by the World Health Organization that can decrease fluid loss in persons with diarrhea. Originally developed to be prepared with materials available in the home, commercial preparations have recently come into use.

Steatorrhea —An excessive amount of fat in the feces due to poor fat absorption in the gastrointestinal tract.



Ahlquist, David A., and Michael Camilleri. "Diarrhea and Constipation." In Harrison's Principles of Internal Medicine , 15th ed. Edited by Eugene Braunwald et al. New York: McGraw-Hill, 2001, pp. 241–9.

Ghishan, Fayez K. "Chronic Diarrhea." In Nelson Textbook of Pediatrics , 17th ed. Edited by Richard E. Behrman et al. Philadelphia: Saunders, 2003, pp. 1276–80.

Greenbaum, Larry A. "Acute Diarrhea and Oral Rehydration." In Nelson Textbook of Pediatrics , 17th ed. Edited by Richard E. Behrman et al. Philadelphia: Saunders, 2003, pp. 249–50.

——. "Diarrhea in Chronically Malnourished Children." In Nelson Textbook of Pediatrics , 17th ed. Edited by Richard E. Behrman et al. Philadelphia: Saunders, 2003, pp. 2250–1.

Sack, R. Bradley. "The Diarrhea of Travelers." In Cecil Textbook of Medicine , 22nd ed. Edited by Lee Goldman et al. Philadelphia: Saunders, 2003, pp. 1864–5.

Semrad, Carol E. and Don W. Powell. "Approach to the Patient with Diarrhea and Malabsorption." In Cecil Textbook of Medicine , 22nd ed. Edited by Lee Goldman et al. Philadelphia: Saunders, 2003, pp. 842–60.


American Academy of Pediatrics. 141 Northwest Point Blvd., Elk Grove Village, IL 60007–1098. Web site: http://www.aap.org.

American College of Gastroenterology. 4900 B South 31st Street, Arlington VA 22206. Web site: http://www.acg.gi.org/.


"Diarrhea." Centers for Disease Control and Prevention. Available online at http://www.cdc.gov/ncidod/dpd/parasiticpathways/diarrhea.htm (accessed January 5, 2005).

"Diarrhea." Merck Manual. Available online at http://www.merck.com/mrkshared/mmanual/section3/chapter27/27b.jsp (accessed January 5, 2005).

"Diarrhea." National Digestive Diseases Information Clearinghouse. Available online at http://digestive.niddk.nih.gov/ddiseases/pubs/diarrhea/ (accessed January 5, 2005).

"Diarrhea." MedlinePlus. Available online at http://www.nlm.nih.gov/medlineplus/diarrhea.html (accessed January 5, 2005).

"Traveler's Diarrhea." American Academy of Family Practice. Available online at http://familydoctor.org/182.xml (accessed January 5, 2005).

L. Fleming Fallon, Jr., MD, DrPH

Also read article about Diarrhea from Wikipedia

User Contributions:

Comment about this article, ask questions, or add new information about this topic: