Gastroenteritis Definition

Gastroenteritis is INFLAMMATION of the SMALL INTESTINE. The most common cause of gastroenteritis is viral INFECTION, though sometimes BACTERIA or PARASITES are responsible. The inflammation of the intestinal mucosa (mucus lining of the intestinal wall) reduces the small intestine’s ability to absorb NUTRIENTS and fluid. People often refer to gastroenteritis as “stomach flu,” though this is inaccurate; the “flu” or influenza is a viral infection of the pulmonary system.

Symptoms of Gastroenteritis and Diagnostic Path

Symptoms of gastroenteritis include DIARRHEA, abdominal cramping, and occasionally ABDOMINAL DISTENTION. Depending on the cause of the infection, the diarrhea can be profuse or bloody; bloody diarrhea requires medical evaluation. There may also be FEVER and VOMITING.

Symptoms that extend beyond two or three days in children or the elderly, or in a person of any age who cannot keep any fluids down, require medical evaluation to prevent DEHYDRATION.

The diagnostic path may include laboratory tests to determine the presence of pathogens (agents of infection) in the stool and blood tests to help identify the extent and nature of infection. The doctor may take stool samples or a rectal swab to determine whether bacterial or parasitic pathogens are present, which would require treatment with the appropriate medications. Bacterial gastroenteritis most often results from consuming contaminated food or water. The doctor may recommend ANTIEMETIC MEDICATIONS to quell nausea and ANTIDIARRHEAL MEDICATIONS to reduce diarrhea, depending on the cause and extent of the symptoms.

Noninfectious forms of gastroenteritis include Crohn’s disease and radiation gastroenteritis. Crohn’s disease is a component of INFLAMMATORY BOWEL DISEASE (IBD), which many doctors believe is an autoimmune disorder with a genetic component in which the IMMUNE SYSTEM attacks the intestinal mucosa. The attacks result in small ulcerations that often bleed. The enteric symptoms are chronic; treatment targets the underlying disease. Radiation gastroenteritis results from damage to the intestinal mucosa that occurs with RADIATION THERAPY to the abdomen, and may be acute (limited to the course of radiation therapy) or chronic (signaling permanent changes in the intestinal mucosa).

PathogenTypeRoute of Infection
astrovirusVIRUScontaminated food or water
calicivirusviruscontaminated food or water
CryptosporidiumPARASITEcontaminated water
Cyclospora cayetanensisparasitecontaminated food or water
enteric adenovirusviruscontaminated food or water
Escherichia coliBACTERIAcontaminated food or water
Giardia lambliaparasitecontaminated water
Listeriabacteriacontaminated food
rotavirusviruscontaminated food or water
Salmonellabacteriacontaminated food
Staphylococcus enterotoxinbacteriacontaminated food

Gastroenteritis Treatment Options and Outlook

Adequate fluid replacement and other supportive measures are the only treatment necessary for viral gastroenteritis, which typically runs its course in three to five days. Young children, older adults, and people who have serious chronic health care conditions are at greatest risk for complications from viral gastroenteritis, though most people recover fully.

Bacterial and parasitic gastroenteritis require treatment with the appropriate medications to eliminate the causative PATHOGEN, and sometimes have a longer course of illness than viral gastroenteritis. Treatment for radiation gastroenteritis focuses on dietary management (eating frequent small meals and foods high in fiber) with ANTIDIARRHEAL MEDICATIONS to help control diarrhea.

Risk Factors and Preventive Measures

Viral gastroenteritis is highly contagious and often occurs in outbreaks, particularly in group settings such as schools, day cares, nursing homes, camps, and contained environments such as cruise ships. These methods can significantly reduce infectious gastroenteritis:

  • proper food handling and preparation
  • frequent and thorough HAND WASHING
  • drinking WATER PURIFICATION (boiling, filtration, chemical)


Gastroenteritis – viral, bacteria, parasite – symptoms and treatment
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