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The Basics of Diarrhea

Diarrhea describes bowel movements (stools) that are loose and watery. It is very common and usually not serious. Many people will have diarrhea once or twice each year. It typically lasts two to three days and can be treated with over-the-counter (OTC) medicines. Some people often have diarrhea as part of irritable bowel syndrome or other chronic diseases of the large intestine.

Doctors classify diarrhea as "osmotic," "secretory," or "exudative."

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  • Osmotic diarrhea means that something in the bowel is drawing water from the body. A common example is sorbitol, a sugar substitute found in sugarless candy and gum that isn't absorbed by the body but draws water into the bowel, resulting in diarrhea.
  • Secretory diarrhea occurs when the body is releasing water into the bowel. Many infections, drugs, and other conditions cause secretory diarrhea.
  • Exudative diarrhea refers to the presence of blood and pus in the stool. This occurs with inflammatory bowel diseases such as Crohn's disease or ulcerative colitis, and several infections.

What Causes Diarrhea?

The most common cause of diarrhea is a virus that infects the gut. The infection usually lasts for two days and is sometimes called "intestinal flu" or "stomach flu." Diarrhea may also be caused by:

  • Infection by bacteria (the cause of most types of food poisoning)
  • Infections by other organisms
  • Eating foods that upset the digestive system
  • Allergies to certain foods
  • Medications
  • Radiation therapy
  • Diseases of the intestines (Crohn's disease, ulcerative colitis)
  • Malabsorption (where the body is unable to adequately absorb certain nutrients from the diet)
  • Hyperthyroidism
  • Some cancers
  • Laxative abuse
  • Alcohol abuse
  • Digestive tract surgery
  • Diabetes
  • Competitive running

Diarrhea may also follow constipation, especially for people who have irritable bowel syndrome.

What Are the Symptoms of Diarrhea?

Symptoms of diarrhea can be broken down into uncomplicated (or non-serious) diarrhea and complicated diarrhea. Complicated diarrhea may be a sign of a more serious illness.

Symptoms of uncomplicated diarrhea include:

  • Abdominal bloating or cramps
  • Thin or loose stools
  • Watery stool
  • Sense of urgency to have a bowel movement
  • Nausea and vomiting

In addition to the symptoms described above, the symptoms of complicated diarrhea include:

  • Blood, mucus, or undigested food in the stool
  • Weight loss
  • Fever

Contact your doctor if you have prolonged diarrhea, bloody diarrhea, or a fever that lasts more than 24 hours. Also see your doctor promptly if vomiting prevents you from drinking liquids to replace lost fluids.

How Is Diarrhea Treated?

If you have a mild case of diarrhea, you can just let it run its course, or you can treat it with an over-the-counter medicine. Common brand names include Pepto-Bismol, Imodium A-D, and Kaopectate, which are available as liquids or tablets. Follow the instructions on the package.

In addition, you should drink at least six 8-ounce glasses of fluid per day. Choose fruit juice without pulp, broth, or soda (without caffeine). Chicken broth (without the fat), tea with honey, and sports drinks are also good choices. Instead of drinking liquids with your meals, drink liquids between meals. Drink small amounts of fluids frequently.

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