Diarrhea is a medical term used to describe an increase in the liquidity or volume of stool or the frequency of bowel movements. Diarrhea is usually described as loose, watery stools, and patients with diarrhea may also experience abdominal pain, abdominal cramping, fever, nausea or blood in the stool.

Different processes in the body may promote diarrhea. These include a failure of the intestines to absorb adequate nutrients and fluids during digestion, the release of too much fluid into the digestive tract or complications that result from intestinal disorders.

Diarrhea can be short-term (acute) or long-term (chronic) in duration. Both types can range in severity, but acute diarrhea lasts for less than four weeks whereas chronic diarrhea continues for more than four weeks.

The most common cause of acute diarrhea is a viral infection (e.g., stomach flu) or bacteria or parasites consumed through contaminated food or water (e.g., food poisoning, traveler's diarrhea).

Chronic diarrhea may indicate a more serious problem, such as irritable bowel syndrome (IBS) or inflammatory bowel disease (IBD). In addition, diarrhea can be a side effect of many different medications, especially antibiotics. Caffeine, alcohol, artificial sweeteners and dairy products may also cause diarrhea in some people. In these cases, the diarrhea usually stops when use of the aggravating agent is discontinued.

Because diarrhea is a symptom of other problems, treatment options will depend on the cause of the diarrhea. In patients with a viral infection, the diarrhea is usually left untreated and resolves itself within a few days. When the diarrhea is caused by certain foodborne bacteria or parasites (e.g., certain forms of E. coli and salmonella), antibiotics may be required to treat the infection. For chronic conditions, such as IBS or IBD, specific medical treatment may be required.

The symptoms of diarrhea, whether acute or chronic, can sometimes be relieved with various over-the-counter and prescription medications. Patients should check with their physician before use, since some of these may interfere with other medications or prolong any infection that might be causing the diarrhea. If a patient is dehydrated as a result of diarrhea, lost fluids and electrolytes will need to be replaced. For most people, this means drinking more fluids until the diarrhea resolves. However, intravenous hydration may be necessary for certain populations for whom diarrhea can become life-threatening such as the very young, the elderly and people with compromised immune systems.