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Loose Stool

What is Diarrhea?

Diarrhea is an increase in the liquidity and/or volume of stool or the frequency of bowel movements. It may be mild, moderate or severe and can have an impact on normal activities. The average frequency of bowel movements and firmness of stool can vary greatly from person to person. Thus, it is important to note any significant changes in what is normal for a particular person. In patients with diarrhea, stool can range from soft to liquid in texture, brown to clear in color, and defecation may occur more than three times a day.

Diarrhea is caused by a disruption of the normal process of digestion. Normal digestion involves food traveling from the stomach to the small intestine, where most nutrients are absorbed. By the time it gets to the colon, only waste material remains. The colon absorbs most of the water from the waste and passes the stool along via muscle contractions (peristalsis) to the rectum at the end of the digestive tract. Diarrhea occurs when too much fluid remains in the intestines as stool travels through the digestive tract. When this occurs, the stool that is eventually passed through the anus is loose and watery.

Too much fluid in the intestines can be caused by several different types of digestive dysfunction, including:

  • The small intestine and colon may fail to absorb enough nutrients and fluids from stool, making the stool loose and watery.
  • The intestines may be stimulated to secrete water, salt or other fluids into the digestive tract, making stool runny. This stimulation can occur as the result of infection, disease or the presence of certain other substances (e.g., castor oil, excess bile acids).
  • Food may pass through the intestines too quickly or in too large an amount to be properly absorbed. The rapid transit of stool through the digestive tract is a common cause of diarrhea.
Diarrhea is a common experience. Millions of Americans report problems with diarrhea every year. It is estimated that the average adult experiences diarrhea approximately four times a year, according to the National Institutes of Health (NIH). It may be difficult to identify exactly how many people have diarrhea, since most people do not seek medical treatment.

Acute diarrhea (lasting less than four weeks) is the most common type of diarrhea. According to the American College of Gastroenterology, it is the second most common reported illness in the United States, after respiratory infections. Most cases of acute diarrhea are caused by infections or antibiotics. Most episodes of acute diarrhea resolve spontaneously (without medications or with simple dietary changes).

As many as 5 percent of Americans have chronic diarrhea (lasting more than four weeks), according to the American Gastroenterological Association. The most common cause of chronic diarrhea in the United States is irritable bowel syndrome (IBS). Chronic diarrhea usually requires medical attention.

How is it diagnosed?

Physicians often rely on a patient’s report of symptoms in diagnosing the cause of and determining treatment for diarrhea. A medical history will include questions about the duration and severity of symptoms, eating habits and current medications. A physical examination will allow a physician to look for signs of illness that may be causing the diarrhea.

Most people with diarrhea will not need extensive testing. When diarrhea goes away by itself, it is not usually necessary to submit to various tests to determine its cause. When tests are used, they may include:

  • Stool tests. Stool is tested for bacteria, parasites or other signs of infection that may be causing the diarrhea.
  • Blood tests. Blood is drawn and tested for evidence of disease that may be causing the diarrhea.
  • Fasting tests. Patients are asked to avoid certain products to determine whether an allergy or food intolerance may be responsible for the diarrhea. Bowel habits are observed to identify whether a change in diet affects the diarrhea. Physicians commonly ask patients to avoid dairy products, carbohydrates and wheat, although other foods may be included. Milk may be purchased with added lactase, and yogurt is usually well tolerated.
  • Endoscopy. A flexible tube (with attached light and camera) is inserted into a patient’s digestive tract to identify any abnormalities that may be causing the diarrhea. Biopsies and color photographs may be taken during this procedure. The tube is inserted via the anus and usually through the entire colon in a colonoscopy. A sigmoidoscopy is similar, but only involves the lower part of the colon (the sigmoid colon).

How is Diarrhea treated?

Antidiarrheal drugs should not be used when diarrhea is caused by an infection because they may prolong the illness.

Dehydration is a serious consequence of diarrhea that should be addressed immediately. Replacement of fluids and electrolytes is required for patients who suffer from dehydration. Sports drinks, which include sodium and potassium, can help restore fluid balance and cardiovascular functioning in the body. Other fluids used to replenish the body after dehydration include fruit drinks, tea, broth and carbonated beverages that have gone flat (contain no fizz). Intravenous rehydration may be necessary for infants or the elderly who are profoundly dehydrated.

In general, treatment for diarrhea will depend on its cause. Diarrhea caused by a viral infection will not respond to antibiotics and will most likely resolve on its own within 24 to 48 hours, depending on the severity of the diarrhea. If diarrhea is the result of invasive bacteria, such as salmonella, antibiotics are sometimes used – especially for patients with compromised immune systems or cardiovascular problems. For chronic diarrhea that is the result of intestinal disorders, specific medical treatment of those disorders may be required.

Many cases of diarrhea can be resolved through changes to diet. Removing alcohol or caffeine products from the diet, for example, may relieve some forms of chronic diarrhea. Dairy products and foods high in fat are other foods that, if removed or limited in a patient’s diet, can help relieve diarrhea. On the other hand, bananas, pears and boiled or mashed potatoes are good sources of potassium, which may be depleted in a person with diarrhea. Adding these food products to a patient’s diet can help restore the balance of nutrients.

In addition, certain prescription and over-the-counter medications (antidiarrheals) can help stop diarrhea. These include:


These medications bind fluids to them, helping stool to be less watery. Adsorbents used to stop diarrhea include bismuth subsalicylate, kaolin and pectin. Patients should check with their physician before using adsorbents, since they may interfere with other medications being taken. In addition, use of certain adsorbents may change stool color to black.

Anti-motility medications

Slows down the contractions of intestinal muscles so that stool travels more slowly through the digestive tract, allowing more fluid to be absorbed by the intestines. Patients should check with their physician before using anti-motility medications to treat diarrhea. If diarrhea is caused by infection, these medications may trap bacteria in the intestines, prolonging the problem.
Other medications may be used to relieve symptoms that occur along with diarrhea for some underlying conditions. For instance, antispasmodics may be used to treat the pain and cramping that occurs with irritable bowel syndrome (IBS).




  • If diarrhea is accompanied by nausea, suck ice chips only.
  • If you are not nauseated, drink small amounts of clear liquids only, such as herbal tea, ginger ale, broth or gelatin until diarrhea stops.
  • Avoid alcohol, caffeine, milk and dairy products.
  • After symptoms disappear, eat soft foods, such as cooked cereal, rice, eggs, custard, baked potato and yogurt for 1 or 2 days.
  • Resume a normal diet 2 or 3 days after the diarrhea stops. Avoid fruit, alcohol and highly seasoned foods for several more days.

What might complicate it?

The most common complications of diarrhea are dehydration and electrolyte imbalance.

Predicted outcome

In over 90% of the cases, acute diarrhea is mild, self-limited, and responds within five days to rehydration therapy or antidiarrheal agents. Individuals with diarrhea caused by infectious agents will recover with appropriate antibiotic therapy. Diarrhea resulting from other causes will improve with treatment of the underlying condition. Individuals with diarrhea of probable immune cause may have chronic inflammation with bouts of diarrhea for years.


Conditions that may result in diarrhea include bowel obstruction, inflammatory bowel disease, irritable bowel syndrome, diabetic neuropathy, or anal sphincter abnormalities.

Appropriate specialists

Internist and gastroenterologist.

Last updated 1 July 2015