What Is Gastroenteritis

Gastroenteritis is the inflammation affecting the lining of the gastrointestinal tract, including both the intestines, and the stomach. Microbial infections and exposure to certain drugs and chemical substances are the usual causes for this condition.

  • Diarrhea accompanied by pain in the abdomen, as well as nausea and vomiting is the usual symptom.
  • Gastrointestinal infections are the usual reason for gastroenteritis, but it can also result from drug use and exposure to toxins.
  • Recent travel involving change in the source of food and water, and close contact with those who are having the disease, are the usual reasons for contracting this disease. Certain diagnostic tests using toxic chemicals, and antibiotic therapy, are the less common reasons for gastroenteritis.
  • Maintaining good hygiene, including frequent washing of hands, especially after bowel movements, and before handling food, help in avoiding microbial infections.
  • Infections caused by certain bacteria can be treated by antibiotic therapy.

Diarrhea is usually the most common, as well as the first sign of gastroenteritis. It can be severe diarrhea or a milder one. Nausea and vomiting, pain, and uneasiness in the stomach, abdominal cramps and loss of appetite are some of the accompanying symptoms. The disease is not usually longstanding and the difficulties caused by it are manageable in healthy people. However, frequent passage of watery stools may result in severe dehydration especially in patients who are very young. In older and weaker people also, gastroenteritis can lead to life threatening complications due to loss of electrolytes and complications developing from dehydration.

Gastroenteritis, due to food contamination, affects one out of every six people each year in the United States alone. The world over, one and a half million deaths occur due to epidemics of gastroenteritis among children. The death toll is highest in less developed countries due to lack of awareness about hygiene and non-availability of medical care.


Gastroenteritis due to microbial infections can spread quickly among people when good hygiene practices are lacking. A person with the disease has the potential to contaminate every object handled, if the hands are not washed thoroughly after every bowel movement. All those who touch contaminated surfaces and then accidentally touch their mouth or handle food with unwashed hands may contract the disease. Any object, which may have traces of stool on it, such as toys and diapers, are potential agents of spreading the disease. This kind of disease transmission is termed as fecal-oral transmission. Water can also be contaminated with fecal matter which may lead to large-scale spread of the disease, usually termed as an outbreak of epidemic. This is very common among people who live in crowded communities. Every time a person consumes uncooked food and water in an area having an outbreak, is at risk of contracting the disease.

Swimming in ponds and pools contaminated by fecal matter from an infected person using it, or from contaminated water entering it, may lead to gastroenteritis. Animals also can be carriers of infectious microbes.  Close interaction with animals or contamination with animal feces also can result in gastroenteritis. The infection causing gastroenteritis may be either bacterial or viral. Parasitic infestation, ingestion of toxic materials and certain drugs are some other causes precipitating gastroenteritis.

Viral Gastroenteritis: Gastroenteritis is often caused by viruses which attack the intestinal lining. They cause severe watery diarrhea accompanied by fever and vomiting. Viral gastroenteritis is a frequent occurrence in the United States.

Mainly there are four kinds of viruses which are responsible for almost all the cases of viral gastroenteritis: They include:

  • Rotavirus
  • Norovirus
  • Astrovirus
  • Enteric adenovirus

Rotavirus infection results in severe diarrhea in very small children aged 3-15 months. It is a highly contagious infection which spreads through the fecal-oral route and causes severe dehydration in the affected children. The infection can be contracted by adults also, but often a mild form of disease results. Rotavirus infections are prevalent in temperate climatic regions, appearing during winter. The infection causes symptoms severe enough to necessitate hospitalization of young children and infants. In the United States, the disease has assumed a recurrent pattern, appearing in the month of November in the Southwest regions, and travelling across the country, ending in March in the Northeast.

Norovirus infections are found in adults and older children, starting mainly from the month of November and lasting till April, even though they may occur at any time of the year. The infection usually spreads through contaminated water and food, but since it is highly infectious, people can directly get it from others on casual interaction.

Astrovirus is spread by the fecal-oral route, mostly affecting young children and infants. Adults also are prone to astrovirus infection, which normally strikes in winter.

Adenovirus is also transmitted via the fecal-oral route. Infants and toddlers below 2 years of age are most prone to this infection. Adenovirus infection can occur at any time of the year but higher incidence is observed in the summer months.

Enterovirus and cytomegalovirus are certain other infective agents generally affecting those who have immune deficiency conditions.

Bacterial Gastroenteritis: Gastroenteritis may be caused by bacterial infections too, but it is less frequent when compared to gastroenteritis due to viral infections. Different bacteria cause diarrhea by different means. Vibrio cholera, Clostridium difficile and certain types of Escherichia coli do not invade the intestinal lining but they attach to it, producing certain chemicals called enterotoxins. These toxic substances trigger the intestinal lining into secreting water as well as minerals precipitating watery diarrhea.

On the other hand, certain other bacteria infiltrate the lining of the intestines, causing damage to the cells. It results in the formation of ulcerations which bleed and leak fluid into the intestines, resulting in diarrhea. The stool may contain red and white blood cells and even traces of blood. Shigella, E. coliSalmonella, and Campylobacter are some of the bacteria of this type.

Diarrhea resulting from Salmonella infection is the most frequent and most dangerous bacterial gastroenteritis prevalent in the United States. Campylobacter bacterial infection also is as frequent. Undercooked meat products, especially poultry, and milk which is not pasteurized, are the major sources of Salmonella and Campylobacter infections. Stools of cats and dogs having diarrhea may spread Campylobacter infections. Salmonella is present in amphibians like salamanders and frogs, reptiles like lizards and turtles, as well as birds. Handling of these animals and raw eggs may result in Salmonella infection.

Another bacterium called Shigella is also responsible for bacterial gastroenteritis in the United States. Person-to-person transmission is the most common route of spreading Shigella infection. Daycare centers are often implicated in the spread of the disease. Occasionally, infection is spread through food.

There are a number of subtypes of E. coli which cause diarrhea. Enterohemorrhagic E. coli which are otherwise called Shiga toxin-producing E. coli results in hemorrhagic colitis. Another condition caused by them is hemolytic-uremic syndrome. E. coliO157:H7 is the most prevalent subtype affecting people in the United States. The source of the infection is usually unpasteurized milk or undercooked ground meat.

 Day care centers are major hubs of E. coli infections. Recreational water illnesses are also large scale infections of E. coli affecting people frequenting open water bodies like lakes, pools, oceans, as well as water parks. Enterotoxigenic E. coli, as the name suggests, produces toxins which result in thin watery stools. Traveler’s diarrhea, affecting visitors to developing countries especially in the tropics, are usually caused by these. Other types of E. coli prevalent in the developing countries may cause bloody diarrhea or nonbloody diarrhea, but it is rare case in the United States.

Certain bacteria, namely, Clostridium perfringens Bacillus cereus,Staphylococcus aureus etc., contaminate the food with a toxin produced by them. Consumption of such foods alone is capable of producing symptoms of gastroenteritis, even in the absence of infection. Symptoms such as nausea and vomiting, accompanied by severe diarrhea, usually start appearing within 12 hours of exposure to the toxin. They may eventually subside within a day or two.

Bacterial Gastroentertis may be caused by many other bacteria but they are not very common in the United States. Appendicitis-like symptoms are precipitated by the infection of Yersinia enterocolitica which may cause gastroenteritis too. The infection usually results from consuming unpasteurized milk, undercooked pork or from water contaminated with the bacteria. Undercooked seafood is the usual source of Vibrio parahaemolyticus infection. Another vibrio bacterium called Vibrio cholera is the cause of cholera epidemics in developing countries. It is characterized watery stools which results in the rapid dehydration of the patient, especially children, many of whom succumb to the infection. This infection quickly spreads in crowded areas like refugee camps. Food contaminated by Listeria can cause gastroenteritis. Plesiomonas shigelloides infection results from the consumption of raw shellfish. People who visit developing countries in the tropical region also contract this infection. Swimming in brackish water and accidentally swallowing the water is the usual reason for the Aeromonas infection.

Parasites: Giardia intestinalis is a parasite inhabiting the intestines and when they bore into the lining, it results in nausea and vomiting, and sometimes diarrhea too. This disease condition known as giardiasis is prevalent in colder regions of the world.  In chronic disease, absorption of nutrients may be impaired, resulting in deficiency diseases due to malabsorption. Contaminated drinking water is the usual channel of transmission, but children in day care centers seem to be getting the infection by contact.

Cryptosporidium parvum is a parasite found in the intestines causing watery stools and other symptoms such as nausea and vomiting as well as abdominal pain. This disease condition known as cryptosporidiosis is usually harmless in normal healthy individuals, but it can be an extremely dangerous and potentially fatal condition in immune-deficient people. Contaminated water is the channel by which Cryptosporidium parvum spreads. It is identified as the culprit of recreational water illness common in the United States, especially since chlorination of water does not affect this organism.

Cyclospora cayetanensis  and Isospora belli  also cause symptoms like that of cryptosporidiosis, especially in people with weakened immune system. Microsporidia is another group of organisms which too cause these symptoms.

 Amebiasis caused by Entamoeba histolytica usually affects the large intestine. Occasionally, it may affect the other organ too including the liver. Though amebiasis is not common in the United States, it is prevalent in many developing countries where bloody diarrhea resulting from it is a common form of gastroenteritis.

Chemical Gastroenteritis: When certain toxic chemicals are ingested it may result in gastroenteritis. The toxins may be biological in origin as in the case of mushroom poisoning and food poisoning from certain seafood. Since chemical gastroenteritis is not caused by any infection, it is not infectious. Toxic chemicals include lead, cadmium, arsenic and mercury. Nausea and vomiting, accompanied by stomach pain as well as diarrhea are the usual symptoms. Excessive consumption of certain food items like tomatoes and citrus fruits may cause gastroenteritis in some people.

Symptoms of Gastroenteritis

Symptoms are typically watery diarrhea as well as nausea and vomiting. But the severity of the symptoms varies from person to person. It usually depends on the causative organism and the toxins produced by them. The immune reaction of the body also determines the severity. Loud stomach sounds, pain and cramping in the abdomen and loss of appetite are other usual symptoms appearing. Blood as well as mucus may be present in the stool. Abdomen may become distended with gas. Fever may be present in some cases. Muscle aches and lethargy may be frequent.

Dehydration developing due to frequent diarrhea and vomiting is a complication of gastroenteritis. Decrease in urine output, dryness of mouth, listlessness and tiredness are some of the indications of dehydration. In infants, signs of dehydration include absence of tears while crying. Loss of minerals and salts may lead to abnormally low potassium levels in the blood called hypokalemia. Dehydration results in the development of low blood pressure due to lowered blood volume. Abnormally fast heart rate may develop. Hyponatremia or lowering of blood sodium levels is a complication if the salts, lost in the stool and vomit, are not replaced by the rehydration therapy. If plain water or light tea is the only liquids used for rehydration there is a high chance of developing low sodium and potassium levels which can become dangerous.  Using ORS solution for rehydration may help prevent this complication, which can otherwise lead to even kidney failure or shock.

Diagnosis Of Gastroenteritis

Gastroenteritis is diagnosed from the typical symptom of frequent watery stool, but the cause of the disease may not be apparent. If it is known that other people in the office or at home have been ill with similar symptoms, the possibility of contracting the same infection is very high. Consuming food contaminated with infectious agents is a major cause of infection. Improperly cooked food, unpasteurized dairy products; raw egg or egg based preparations like mayonnaise, carry the risk of infection with Salmonella. Antibiotic use is another cause of diarrhea; so is travel to other places and countries.

If diarrhea does not resolve in a day or two, a sample of the stool should be tested to identify the organism causing the disease such as bacteria or parasites.

A sigmoidoscopy is usually done if the diarrhea continues for more than a few days. With a viewing tube called sigmoidoscope, the large bowel is checked for abnormalities as well as for the presence of ulcerative colitis.

Prevention of Gastroenteritis

Oral vaccines available against rotavirus are effective against the most common strains of virus. These vaccinations help prevent viral gastroenteritis in young children, especially in those who spend time in daycare centers. Hygiene measures are important while changing diapers and feeding children. Diapers should be changed in designated areas and the areas should be cleaned with a bleach solution. Hands should be thoroughly scrubbed with soap and water after every diaper change. The soiled diapers and cleaning tissues should be disposed off promptly. When children have diarrhea, they should be kept away from daycare centers till the symptoms are resolved. Infections with Shigella, as well as E. coli infection resulting in bloody diarrhea, should be treated with care. Children affected should test negative twice, before returning to the day care.

To avoid contracting Salmonella infection, children should be kept away from amphibian and reptilian animals which are likely to carry the bacteria. Older individuals with lower immunity level also should avoid contact with animals.

Frequent washing of hands with soap and water will reduce the chances of contracting the disease to a great extent. Contact with people who are infected is the most common method of transmission. People who have diarrhea should wash their hands thoroughly after every bowel movement. Clothes contaminated with stool should not be mixed with other washing load. Soiled clothes should be washed separately. To avoid contaminating food, hand washing before meals as well as before touching any instruments such as knives, cutting boards, cooking vessels, spoons etc., associated with cooking and serving food should be strictly practiced. Instruments and vessels which have come in contact with raw meat and eggs should be washed separately. Meat should be cooked properly and should be quickly cooled down and refrigerated before microbes get chance to grow and multiply. Milk should be consumed after boiling thoroughly or pasteurized milk should be used. Raw egg products such as mayonnaise should also be pasteurized. Eating street foods should be avoided especially while traveling.

When a person is having diarrhea, swimming in a community pool should be strictly avoided to prevent the spread of recreational water illness. The diapers of toddlers and infants should be checked and changed away from the pool. Ingesting water during swimming should be avoided.

Treatment Of Gastroenteritis

Rehydration therapy is the most essential and effective treatment for gastroenteritis. With sufficient intake of fluids and a good rest the body may overcome the infection in a few days without any further treatment. Rehydration therapy should be tailored to the condition of the patient and the symptoms of the disease. If vomiting is present, the patient may not be able to tolerate oral intake of fluids. Very small quantities of liquids, mostly one sip at a time, may be administered frequently. If it is not sufficient to maintain satisfactory hydration, intravenous administration should be initiated without delay.

 A home-made salt sugar mixture advised for oral dehydration is found to be as effective as the commercially available oral rehydration (ORS) mixtures in saving lives, especially among children in underdeveloped countries. Breast feeding of younger babies should be continued during the disease in addition to spoon feeding of small quantities of ORS. Tea, coffee, colas, fruit juices, energy drinks, alcohol etc., should be avoided. A drug to reduce vomiting is often given to adult patients but it is not given to younger children and babies. The antiemetic drug can be given in the form of a suppository or it can be injected as oral administration may not be ideal in severe cases of vomiting.

Normal diet can be resumed as and when the disease is under control but new foods should be added with gradually depending on the patient’s reception. People generally limit their choice to bland and mild food items like rice, toast, bananas and cooked apple, though diet restrictions are unnecessary. Some people may not tolerate certain foods, especially milk, immediately following a bout of diarrhea. Use of lactobacillus culture, available in powder form also, often help people get over the intolerance of milk.

The stool is tested to identify the causative organism and for the presence of blood. Traces of blood in the stool may indicate a serious infection which should be tackled first. If blood is not detected, the patient may be given antidiarrheal drug if the watery stools do not stop in a day or two. diphenoxylate is an antidiarrheal drug often prescribed. Loperamide is another drug which is available over the counter. These antidiarrheal drugs are effective in controlling diarrhea, but children below five years should not use them.

The use of antibiotics in the treatment has certain problems. It may result in drug -induced diarrhea as the antibiotics destroy beneficial bacteria in the intestine making way for the proliferation of certain harmful bacteria like Clostridium difficile. During stool testing, if the cause is found to be certain organisms such as Shigella, Campylobacter and Vibrio, antibiotic therapy is initiated. Traveler’s diarrhea is another instance in which antibiotic therapy is used to treat gastroenteritis.

Intestinal parasites can be eradicated by the use of drugs metronidazole as well as nitazoxanide which are antiparasitic medication.

Some beneficial bacteria found in the gastrointestinal tract are useful in creating a favorable environment for the growth of good microbes while suppressing the proliferation of harmful organisms. Such bacterial cultures called probiotics are useful in managing the diarrhea and reducing the duration of the disease. An example of probiotics is yogurt containing the beneficial bacteria lactobacillus. In severe cases of gastroenteritis probiotics may not have much effect. To control fluid and electrolyte loss which may lead to severe complications, the patient with acute gastroenteritis should be hospitalized for intravenous dehydration therapy.

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Yasser Elnahas

MD, PHD, Professor Of CardioVascular Surgery
Dr. Yasser Elnahas, Is an associate Professor of Cardiovascular Surgery. Dr. Elnahas was trained as a fellow At Texas Heart Institute And Mayo Clinic Foundation.Dr. Elnahas is dedicated to educating the general public about different disease conditions and simplifying the medical knowledge in an easy to understand terminology.

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