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Gastroenteritis
(Stomach Flu)

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Medical Author:

Charles Patrick Davis, MD, PhD

Charles Patrick Davis, MD, PhD

Dr. Charles "Pat" Davis, MD, PhD, is a board certified Emergency Medicine doctor who currently practices as a consultant and staff member for hospitals. He has a PhD in Microbiology (UT at Austin), and the MD (Univ. Texas Medical Branch, Galveston). He is a Clinical Professor (retired) in the Division of Emergency Medicine, UT Health Science Center at San Antonio, and has been the Chief of Emergency Medicine at UT Medical Branch and at UTHSCSA with over 250 publications.

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Medical Editor:

Bhupinder Anand, MD

What is gastroenteritis?

Gastroenteritis is inflammation of the gastrointestinal tract, involving the stomach, intestines, or both; usually resulting in diarrhea, abdominal cramps, nausea and possibly vomiting. Gastroenteritis is frequently termed "stomach flu" or "gastric flu" because the most frequent cause of gastroenteritis is viral. However, this loose terminology confuses some people because influenza viruses (flu viruses) do not cause gastroenteritis.

Gastroenteritis also can be confusing to people because gastroenteritis itself is considered a disease, but gastroenteritis can also be considered a symptom of other diseases. For example, a person who has the symptoms of gastroenteritis and eventually develops bloody diarrhea is usually not diagnosed with gastroenteritis, but with a specific disease such as shigellosis. Unfortunately, there are many specific diseases that manifest with symptoms of gastroenteritis, usually early in the disease process.

To complicate things even more, often confusion is generated when the term gastroenteritis is modified by words like "mild" or "severe." "Severe gastroenteritis" is a non-specific term that usually means different things to different investigators. The meaning is usually implied by the disease process that is being discussed. For example, if the context of an article about a viral cause of gastroenteritis, it often means diarrhea that causes dehydration; while another article about a bacterial cause of gastroenteritis it may mean bloody diarrhea with fever.

The best way to sort out this non-specific terminology associated with gastroenteritis is for authors and health care practitioners to define what they mean by gastroenteritis and its modifying terms. While there may be disagreement about the terms, at least their meaning will be clear to the readers of individual articles. Consequently, for this article, gastroenteritis will mean the short-term (lasting about 2 to 5 days and resolution, sometime over an additional few days) occurrence of symptoms that may include some or all of the following:

• Non-bloody diarrhea
  
  
• Nausea
  
  
• Vomiting (occasional, less than 48 hours)
  
  
• Abdominal cramping (intermittent, usually relieved by a bowel movement)

Other symptoms may develop such as a mild fever (about 100 F, 37.7 C), mild chills, occasionally a headache, and/or muscle aches, and a feeling of being tired. All of the above symptoms may develop into severe gastroenteritis which means for this article, dehydration, which may be life-threatening, especially in children.

People with symptoms of diarrhea, bloody diarrhea, nausea, or vomiting that lasts more than five days, and often may have additional symptoms of fever (greater than 101 F, 38.3 C), malaise, dehydration, and sepsis, for this article, will not be considered to have gastroenteritis. However, people with such problems will be considered to have symptoms of gastroenteritis that are related to a specific disease, for example, shigellosis.

Not all investigators will agree with this designation and consider bloody diarrhea, vomiting more than 48 hours, fever higher than 101 F (38.3 C), dehydration, and relatively constant abdominal pain as severe gastroenteritis. However, these symptoms are not frequently associated with gastroenteritis or stomach flu that does not run a limited course, and does not resolve without professional or medical treatment, and are more often associated with other specific diseases, most of which require medical care.

Most children and adults diagnosed with shigellosis, E. coli 0157:H7 infections, salmonellosis, and other diseases are usually not diagnosed as having severe gastroenteritis or severe stomach flu. Readers may wonder why then, should such pathogens be listed as causes of gastroenteritis. The answer is simple. The pathogens are listed because in many people, the pathogens produce only symptoms of gastroenteritis and do not go on to develop worse symptoms, often because an otherwise healthy person self-limits the infection. Not to list them would not give an accurate summation of the causes of gastroenteritis.