November 11, 2009


Gastroenteritis is inflammation of the lining of the stomach and small and large intestines. It is usually caused by infection wit
h a microorganism but can also be caused by ingestion of chemical toxins or drugs.

*The infection is usually caused by an infection but can be caused by ingesting toxins or drugs.

*Typically, people have diarrhea, nausea, vomiting, and abdominal pain.

*The diagnosis is based on some laboratory tests and a person's history of recent contact with contaminated people, food, or water or antibiotic use.

*Thoroughly washing the hands after a bowel movement or contact with fecal matter is the best way to prevent infection.

*Antibiotics are used to eliminate only certain kinds of bacteria.

Gastroenteritis usually consists of mild to severe diarrhea that may be accompanied by loss of appetite, nausea, vomiting, cramps, and discomfort in the abdomen. Although gastroenteritis usually is not serious in a healthy adult, causing only discomfort and inconvenience, it can cause life-threatening dehydration (see Water Balance: Dehydration) and electrolyte imbalance (see Minerals and Electrolytes: Electrolytes) in the very ill or weak, the very young, and the very old. About 3 to 6 million children around the world die each year from infectious gastroenteritis


Infections that cause gastroenteritis can be transmitted from person to person, especially if people with diarrhea do not thoroughly wash their hands after a bowel movement. Infection also can occur if people touch their mouth after touching an object (such as a diaper or toy) contaminated by infected stool. All such transmission involving infected stool is termed “fecal-oral transmission.” A person, and sometimes large numbers of people (in which case an outbreak of illness is called an epidemic), can also become infected by eating food or drinking water that has been contaminated by infected stool. Most foods can be contaminated with bacteria and cause gastroenteritis if not cooked thoroughly or pasteurized. Contaminated water is sometimes ingested in unexpected ways, such as when swimming in a pond contaminated by stool from an animal or in a swimming pool contaminated by stool from another person. In some cases, gastroenteritis is acquired through contact with animals that carry the infectious microorganism.

Infectious gastroenteritis may be caused by viruses, bacteria, or parasites. Chemical toxins and drugs can also cause gastroenteritis.

Viruses: Viruses are the most common cause of gastroenteritis in the United States. Certain viruses infect cells in the lining of the small intestine where they multiply and cause watery diarrhea, vomiting, and fever. Four categories of viruses cause most gastroenteritis: rotavirus, calicivirus (predominantly the norovirus), and less commonly, astrovirus, and enteric (intestinal) adenovirus.

Rotavirus is the most common cause of severe, dehydrating diarrhea in young children. It usually affects those between the ages of 3 months and 15 months. Rotavirus is highly contagious. Most infections are spread by fecal-oral transmission. Adults may be infected after close contact with an infected infant, but the illness is generally mild. During the winter in temperate climates, rotavirus causes most cases of diarrhea that are serious enough to send infants and toddlers to the hospital. Each year in the United States, a wave of rotavirus illness begins in the Southwest in November and ends in the Northeast in March.

Norovirus most commonly infects older children and adults. Infections occur year-round. Most people are infected after swallowing contaminated food or water. Because norovirus is highly contagious, infection can easily be spread from person to person.

Astrovirus can infect people of all ages but usually infects infants and young children. Infection is most common in the winter and is spread by fecal-oral transmission.

Adenovirus most commonly affects children under the age of 2. Infections occur year-round and increase slightly in the summer. The infection is spread by fecal-oral transmission.

Other viruses (such as cytomegalovirus and enterovirus) can cause gastroenteritis in people who have an impaired immune system.
Bacteria: Bacterial gastroenteritis is less common than viral gastroenteritis.
Parasites: Certain intestinal parasites, particularly Giardia lamblia, stick to or invade the lining of the intestine and cause nausea, vomiting, diarrhea, and a general sick feeling. The resulting infection, called giardiasis, is more common in cold climates but occurs in every region of the United States and throughout the world. If the disease becomes persistent (chronic), it can keep the body from absorbing nutrients, a condition known as a malabsorption syndrome. Infection is usually spread through person-to-person contact (often in day care centers) or from contaminated water.

Chemical Gastroenteritis: Gastroenteritis may result from ingesting chemical toxins. These toxins are usually produced by a plant, such as poisonous mushrooms, or by certain kinds of exotic seafood and thus are not the product of an infection. Gastroenteritis due to chemical toxicity can also occur after ingesting water or food contaminated by chemicals such as arsenic, lead, mercury, or cadmium. Heavy-metal poisoning frequently causes nausea, vomiting, abdominal pain, and diarrhea. Eating large amounts of acidic foods, such as citrus fruits and tomatoes, gives some people gastroenteritis.


The type and severity of the symptoms depend on the type and quantity of microorganism or toxin ingested. Symptoms also vary according to the person's resistance. Symptoms often begin suddenly—sometimes dramatically—with a loss of appetite, nausea, or vomiting. Audible rumbling of the intestine and abdominal cramping may occur. Diarrhea is the most common symptom and may be accompanied by visible blood and mucus. Loops of intestine may be painfully swollen (distended) with gas. The person may have a fever, feel generally sick, and experience aching muscles and extreme exhaustion.

Severe vomiting and diarrhea can lead to marked dehydration. Symptoms of dehydration include weakness, decreased frequency of urination, dry mouth, and, in infants, lack of tears when crying. Excessive vomiting or diarrhea can result in low levels of potassium in the blood (hypokalemia). Low blood pressure and a rapid heart rate can also develop. Low levels of sodium in the blood (hyponatremia) also may develop, particularly if the person replaces lost fluids by drinking fluids that contain little or no salt, such as water and tea. Water and electrolyte imbalances are potentially serious, especially in the young, the old, and people with chronic diseases. Shock and kidney failure can occur in severe cases.


The diagnosis of gastroenteritis is usually obvious from the symptoms alone, but the cause often is not. Sometimes other family members or coworkers have recently been ill with similar symptoms. Other times, gastroenteritis can be traced to contaminated water or inadequately cooked, spoiled, or contaminated food, such as raw seafood or mayonnaise left out of the refrigerator too long. Recent travel, especially to certain foreign countries, and recent antibiotic use may give clues as well.

If the symptoms are severe or last for more than 48 hours, stool samples may be cultured and examined in a laboratory for white blood cells and bacteria, viruses, or parasites.

If the symptoms persist beyond a few days, a doctor may need to examine the large intestine with a colonoscope (a flexible viewing tube used to view the lower part of the digestive tract) to determine whether the person has a disease such as ulcerative colitis.


A rotavirus vaccine given by mouth is now available that is safe and effective against most strains of rotavirus. This vaccine is now part of the recommended infant vaccination schedule and is given at 2, 4, and 6 mo of age

For infants, a simple and effective way to prevent gastroenteritis is breastfeeding. Caregivers should wash their hands thoroughly with soap and water after changing diapers, and diaper-changing areas should be disinfected with a freshly prepared solution of household bleach (¼ cup bleach diluted in 1 gallon of water). Children with diarrhea should be excluded from child care centers for the duration of their symptoms. Children infected with E. coli that causes bloody diarrhea or Shigella should also have two negative stool cultures before they are allowed to return to the center.

Because most infections that cause gastroenteritis are transmitted by person-to-person contact, particularly through direct or indirect contact with infected stool, good hand washing with soap and water after a bowel movement is the most effective means of prevention. To prevent food-borne infections, hands should be washed before touching food, knives and cutting boards used to cut raw meat should be washed before use with any other food, meat and eggs should be cooked thoroughly, and leftovers should be refrigerated promptly after cooking. Only pasteurized dairy products and pasteurized apple juice should be used. Travelers should try to avoid possibly contaminated food and drink.


Usually the only treatment needed for gastroenteritis is getting bed rest and drinking an adequate amount of fluids. Even a person who is vomiting should drink as much as can be tolerated, taking small frequent sips. If vomiting or diarrhea is prolonged or the person becomes severely dehydrated, intravenous fluids and electrolytes may be needed. Because children can become dehydrated more quickly, they should be given fluids with the appropriate mix of salts and sugars. Any of the commercially available solutions designed to replace lost fluids and electrolytes (rehydration solutions) are satisfactory. Carbonated beverages, teas, sports drinks, beverages containing caffeine, and fruit juices are not appropriate. If the child is breastfed, breastfeeding should continue. Drugs that control severe vomiting are not generally given to young children. For adults, a doctor may give a drug, either as an injection or as a suppository, to control severe vomiting.

As the symptoms subside, the person may gradually add foods to the diet. Traditionally, bland foods such as cereal, gelatin, bananas, rice, applesauce, and toast are given, but there is no evidence that these are superior to other foods. If the diarrhea continues for 24 to 48 hours and there is no blood in the stool to indicate a more serious bacterial infection, the doctor may prescribe a drug to control the diarrhea, such as diphenoxylate, or instruct the person to use an over-the-counter drug, such as loperamide. Again, these drugs usually are not given to children under the age of 5.

Because antibiotics can cause diarrhea and may encourage the growth of organisms resistant to antibiotics, they are rarely appropriate, even when a known bacterium is causing gastroenteritis. Antibiotics may be used, however, when certain bacteria, such as Campylobacter, Shigella, and Vibrio, are the cause, and for people who have traveler's diarrhea.

Parasitic infections are treated with antiparasitic drugs such as metronidazole and nitazoxanide
Some bacteria are naturally found in the body and promote the growth of good bacteria (probiotics). The use of probiotics, such as lactobacillus (normally found in the mouth, digestive tract, and vagina), is generally safe and may relieve symptoms. They can be given in the form of yogurt with active cultures.
Adapted from: Merch & Co., Inc
The following chart illustrates the progressive diet to be used when experiencing episodes of gastroenteritis, and is intended as a guide only. As the diet expands, beverages or foods from preceding columns are included. If symptoms recur or become worse, the diet should regress back to FULL LIQUID or CLEAR LIQUID recommendations and your health care provider contacted.
Notify your health care provider if you have any of the following symptoms:
  • Not able to keep liquids down after 24 hours
  • You have been vomiting for more than two days
  • You are vomiting blood
  • You are dehydrated. Signs of dehydration include; excessive thirst, dry mouth, deep yellow urine or little or no urine, severe weakness, dizziness or lightheadedness
  • You notice blood in your bowel movements
  • You have a fever above 101° F
  • Pain that is localized, especially in the right lower abdomen
  • Other symptoms develop that worry you
Adapted from: McKinley Health Center