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Gastroenteritis

By

Thomas G. Boyce

, MD, MPH, University of North Carolina School of Medicine

Last full review/revision Jun 2019| Content last modified Jun 2019
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Gastroenteritis is inflammation of the lining of the stomach and small and large intestines. It is usually caused by infection with a microorganism but can also be caused by ingestion of chemical toxins or drugs.

  • Gastroenteritis 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 a person’s history of recent contact with contaminated food, water, or people infected with certain microorganisms; recent use of antibiotics; and sometimes laboratory tests.

  • Thoroughly washing the hands after a bowel movement or contact with fecal matter and avoidance of undercooked foods are the best ways to prevent infection.

  • Antibiotics are used to treat only certain kinds of bacteria that cause gastroenteritis.

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 Dehydration Dehydration is a deficiency of water in the body. Vomiting, diarrhea, excessive sweating, burns, kidney failure, and use of diuretics may cause dehydration. People feel thirsty, and as dehydration... read more and electrolyte imbalance Electrolyte Balance read more in the very ill or weak, the very young, and the very old. Each year in the United States, about 1 in 6 people develops gastroenteritis by eating contaminated food. About 1.5 to 2.5 million children around the world die each year from infectious gastroenteritis Gastroenteritis in Children Gastroenteritis is inflammation of the digestive tract that results in vomiting, diarrhea, or both and is sometimes accompanied by fever or abdominal cramps. Gastroenteritis is usually caused... read more .

Causes of Gastroenteritis

The most common causes of gastroenteritis are

  • Viruses (most common)

  • Bacteria

  • Parasites

Other causes include

  • Chemical toxins

  • Drugs

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 direct contact with animals that carry the infectious microorganism.

Viruses

Viruses Overview of Viral Infections A virus is composed of nucleic acid, either DNA or RNA, surrounded by a protein coat. It requires a living cell in which to multiply. A viral infection can lead to a spectrum of symptoms from... read more 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: norovirus, rotavirus, and, less commonly, astrovirus and enteric (intestinal) adenovirus.

Norovirus infects people of all ages. It is now the most common cause of gastroenteritis in the United States. Infections occur year-round, but 80% occur from November to April. Most people are infected after swallowing contaminated food or water. Because norovirus is highly contagious, infection can easily be spread from person to person. This virus causes most cases of gastroenteritis epidemics on cruise ships and in nursing homes.

Rotavirus Rotavirus Infection Rotavirus is a common and very contagious virus that causes vomiting and diarrhea. Rotavirus is a viral infection of the digestive tract that can cause severe dehydration. Typical symptoms include... read more Rotavirus Infection is the most common cause of severe, dehydrating diarrhea among young children worldwide. Its incidence in the United States has decreased by 80% since rotavirus vaccines were added to the routine vaccination schedule Childhood Vaccination Schedule Most doctors follow the vaccination schedule recommended by the Centers for Disease Control and Prevention (CDC—see the schedule for infants and children and the schedule for older children... read more . 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. In temperate climates, most infections occur in the winter. Each year in the United States, a wave of rotavirus illness begins in the Southwest in November and ends in the Northeast in March.

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.

Did You Know...

  • Worldwide, about 1.5 to 2.5 million children die each year from gastroenteritis caused by an infection.

Bacteria

Some bacteria (such as certain strains of E. coli Escherichia coli Infections Escherichia coli (E. coli) are a group of gram-negative bacteria that normally reside in the intestine of healthy people, but some strains can cause infection in the digestive tract, urinary... read more , Campylobacter Campylobacter Infections Several species of the gram-negative bacteria Campylobacter (most commonly Campylobacter jejuni) can infect the digestive tract, often causing diarrhea. People can be infected when they consume... read more , Shigella Shigellosis Shigellosis is infection by the gram-negative bacteria Shigella. It results in watery diarrhea or dysentery (the frequent and often painful passage of small amounts of stool that contains blood... read more , Salmonella Salmonella Infections The gram-negative bacteria Salmonella typically cause diarrhea and sometimes cause a more serious infection, typhoid fever. People are usually infected when they eat contaminated food, such... read more , and Clostridium difficile Overview of Clostridial Infections Clostridia are bacteria that commonly reside in the intestine of healthy adults and newborns. Clostridia also reside in animals, soil, and decaying vegetation. These bacteria do not require... read more ) invade the lining of the small intestine or colon. There, they damage cells, causing tiny sores (ulcerations) that bleed, and allow a considerable leakage of fluid containing proteins, electrolytes, and water. The diarrhea contains white and red blood cells and sometimes visible blood.

Salmonella and Campylobacter are common bacterial causes of diarrhea in the United States. Both infections are most frequently acquired from eating undercooked poultry. Unpasteurized milk is also a possible source. Campylobacter is occasionally transmitted by dogs or cats with diarrhea. Salmonella can be transmitted by eating undercooked eggs and by having contact with reptiles (such as turtles or lizards), birds, or amphibians (such as frogs and salamanders).

Species of Shigella are also a common bacterial cause of diarrhea in the United States and are usually transmitted person to person (especially in day care centers), although foodborne outbreaks occur.

Clostridium difficile is now probably the most common bacterial cause of diarrhea in the United States and is the most common cause of diarrhea that occurs after treatment with antibiotics (see Gastroenteritis as a Side Effect of Drugs Gastroenteritis as a Side Effect of Drugs Gastroenteritis is inflammation of the lining of the stomach and small and large intestines. It is usually caused by infection with a microorganism but can also be caused by ingestion of chemical... read more Gastroenteritis as a Side Effect of Drugs ). However, it sometimes occurs in people who have not been treated with antibiotics. Antibiotics kill the healthy bacteria that normally reside in the intestines, which allows Clostridium difficile bacteria to grow in their place. Clostridium difficile produces a toxin that causes severe watery diarrhea (see also Clostridium difficile–induced diarrhea Clostridioides (formerly Clostridium) difficile-Induced Colitis Clostridioides difficile (C. difficile)–induced colitis is an inflammation of the large intestine (colon) that results in diarrhea. The inflammation is caused by toxin produced by C. difficile... read more ).

Several other bacteria cause gastroenteritis, but most are rare in the United States. Yersinia enterocolitica Plague and Other Yersinia Infections Plague is a severe infection caused by the gram-negative bacteria Yersinia pestis and often involving the lymph nodes and/or lungs. The bacteria are spread mainly by the rat flea. Depending... read more Plague and Other <i>Yersinia</i> Infections can cause gastroenteritis or a syndrome that mimics appendicitis. A person is infected after ingesting undercooked pork, unpasteurized milk, or contaminated water. Several Vibrio Cholera Cholera is a serious infection of the intestine that is caused by the gram-negative bacteria Vibrio cholerae and that causes severe diarrhea, which can be fatal without treatment. People are... read more species (such as Vibrio parahaemolyticus) cause diarrhea after ingesting undercooked seafood. Vibrio cholerae, which is responsible for the watery diarrhea that is the main symptom of cholera Cholera Cholera is a serious infection of the intestine that is caused by the gram-negative bacteria Vibrio cholerae and that causes severe diarrhea, which can be fatal without treatment. People are... read more , sometimes causes severe dehydrating diarrhea in developing countries. Epidemics may occur after natural disasters or in refugee camps. Listeria Listeriosis Listeriosis is infection caused by the gram-positive bacteria Listeria monocytogenes, usually when contaminated food is eaten. People may consume the bacteria in contaminated dairy products... read more can rarely cause foodborne gastroenteritis but more often causes a bloodstream infection or meningitis in pregnant women, newborns, or older people. Aeromonas is acquired from swimming in or drinking contaminated fresh water or briny, salty water. Plesiomonas shigelloides can cause diarrhea in people who have eaten raw shellfish or traveled to tropical regions in developing countries.

Parasites

Certain intestinal parasites, particularly Giardia intestinalis, stick to or invade the lining of the intestine and cause nausea, vomiting, diarrhea, and a general sick feeling. The resulting infection, called giardiasis Giardiasis Giardiasis is an infection of the small intestine caused by the single-celled protozoan parasite Giardia. The main symptoms are abdominal cramping and diarrhea. People may have abdominal cramping... read more , 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 Overview of Malabsorption Malabsorption syndrome refers to a number of disorders in which nutrients from food are not absorbed properly in the small intestine. Certain disorders, infections, and surgical procedures can... read more . Infection is usually spread through drinking contaminated water (sometimes from wells or unconventional water sources encountered while hiking or camping) or, less commonly, via person-to-person contact (such as in day care centers).

Another intestinal parasite, called Cryptosporidium parvum, causes watery diarrhea that is sometimes accompanied by abdominal cramps, nausea, and vomiting. The resulting infection, called cryptosporidiosis Cryptosporidiosis Cryptosporidiosis is an intestinal infection caused by Cryptosporidium, a protozoan parasite. The main symptoms are abdominal cramping and diarrhea. People acquire the infection by consuming... read more Cryptosporidiosis , is usually mild in otherwise healthy people, but it may be severe or even fatal in people with a weakened immune system. It is most commonly acquired by drinking contaminated water. Because it is resistant to usual concentrations of chlorine, this parasite is the most common cause of recreational water illness in the United States.

Other parasites that can cause symptoms similar to those of cryptosporidiosis include Cyclospora cayetanensis and, in people with an impaired immune system, Cystoisospora belli and a collection of organisms referred to as microsporidia Microsporidiosis Microsporidiosis is infection caused by Microsporidia, which are parasitic fungi. Symptoms depend on the organs infected, but infections can cause diarrhea, other intestinal symptoms, or eye... read more . Entamoeba histolytica causes amebiasis Amebiasis Amebiasis is an infection of the large intestine and sometimes the liver and other organs that is caused by the single-celled protozoan parasite Entamoeba histolytica, an ameba. The amebas may... read more , an infection of the large intestine and sometimes the liver and other organs. Amebiasis is a common cause of bloody diarrhea in developing countries but is rare in the United States.

Chemical gastroenteritis

Gastroenteritis may result from ingesting chemical toxins (see Overview of Food Poisoning Overview of Food Poisoning Food poisoning results from eating a plant or animal that contains a toxin. The poisoning occurs after ingesting poisonous species of mushrooms or plants or contaminated fish or shellfish. The... read more ). These toxins are usually produced by a plant, such as poisonous mushrooms Mushroom (Toadstool) Poisoning Many species of mushroom are poisonous. The potential for poisoning may vary within the same species, at different times of the growing season, and with cooking. It is difficult to differentiate... read more , or by certain kinds of exotic seafood Fish and Shellfish Poisoning Gastroenteritis may be caused by eating bony fish or shellfish. There are three common types of poisoning caused by eating bony fish: Ciguatera Tetrodotoxin Scombroid (See also Shellfish poisoning.) read more 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 Lead Poisoning Some causes of lead poisoning are ingesting lead paint and eating or drinking from certain imported, improperly lead-glazed ceramics. Very high levels of lead in the blood may cause personality... read more , 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.

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Gastroenteritis as a Side Effect of Drugs

Nausea, vomiting, and diarrhea are common side effects of many drugs. Common offenders include

  • Antacids containing magnesium as a major ingredient

  • Antibiotics

  • Chemotherapy drugs

  • Radiation therapy

  • Colchicine (for gout)

  • Digoxin (usually used for heart failure or certain irregular heart rhythms)

  • Drugs used to remove or destroy internal parasitic worms

  • Laxatives

Laxative abuse can lead to weakness, vomiting, diarrhea, electrolyte loss, and other disturbances.

Recognizing that a drug is causing gastroenteritis can be difficult. In mild cases, a doctor can have a person stop taking the drug and later start taking it again. If the symptoms subside when the person stops taking the drug and resume when the person starts taking the drug again, then the drug may be the cause of the gastrointestinal symptoms. In severe cases of gastroenteritis, a doctor may instruct the person to stop taking the drug permanently.

Symptoms of 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 have aching muscles and extreme exhaustion.

Gastroenteritis caused by viruses

Viruses cause watery diarrhea. Stools rarely contain mucus or blood.

Rotavirus may last 5 to 7 days in infants and young children. Vomiting occurs in most children, and some have fever.

Norovirus causes more vomiting than diarrhea and lasts only 1 to 2 days.

Adenovirus causes mild vomiting 1 to 2 days after diarrhea starts. The diarrhea can last 1 to 2 weeks.

Astrovirus symptoms are similar to a mild rotavirus infection.

Gastroenteritis caused by bacteria

Bacteria are likely to cause fever and may cause bloody or watery diarrhea. Some bacteria also cause vomiting.

Gastroenteritis caused by parasites

Parasites typically cause diarrhea that may last for a long time and may cause diarrhea that comes and goes. The diarrhea is usually not bloody. People may be very tired and lose weight when they have long-lasting diarrhea caused by a parasitic infection.

Complications of gastroenteritis

Severe vomiting and diarrhea can lead to marked dehydration Dehydration Dehydration is a deficiency of water in the body. Vomiting, diarrhea, excessive sweating, burns, kidney failure, and use of diuretics may cause dehydration. People feel thirsty, and as dehydration... read more . 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 electrolyte problems Overview of Electrolytes Well over half of the body's weight is made up of water. Doctors think about the body's water as being restricted to various spaces, called fluid compartments. The three main compartments are... read more such as low levels of potassium in the blood Hypokalemia (Low Level of Potassium in the Blood) In hypokalemia, the level of potassium in blood is too low. A low potassium level has many causes but usually results from vomiting, diarrhea, adrenal gland disorders, or use of diuretics. A... read more (hypokalemia) and dehydration Dehydration Dehydration is a deficiency of water in the body. Vomiting, diarrhea, excessive sweating, burns, kidney failure, and use of diuretics may cause dehydration. People feel thirsty, and as dehydration... read more , which can cause low blood pressure and a rapid heart rate. Low levels of sodium in the blood Hyponatremia (Low Level of Sodium in the Blood) In hyponatremia, the level of sodium in blood is too low. A low sodium level has many causes, including consumption of too many fluids, kidney failure, heart failure, cirrhosis, and use of diuretics... read more (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.

Diagnosis of Gastroenteritis

  • A doctor's evaluation

  • History of contact with contaminated food or water or recent travel or antibiotic use

  • Sometimes stool tests

  • Sometimes sigmoidoscopy

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 examined in a laboratory for white blood cells and bacteria, viruses, or parasites.

Seriously ill people may need blood tests to determine whether they have water and electrolyte imbalances or tests to determine how their kidneys are functioning.

Prevention of Gastroenteritis

  • Vaccination

  • Hygiene

  • Breastfeeding

For infants, a simple and effective way to help prevent gastroenteritis is breastfeeding Breastfeeding Breast milk is the ideal food for newborns. Although babies may be fed breast milk or formula, doctors recommend exclusive breastfeeding for at least the first 6 months and introducing appropriate... read more Breastfeeding . Caregivers should wash their hands thoroughly with soap and water before preparing bottles for formula-fed infants. They should also wash their hands after changing diapers. 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 day care centers for the duration of their symptoms. Children infected with E. colithat causes bloody diarrhea or Shigella should also have two negative stool tests before they are allowed to return to the center.

Did You Know...

  • It takes 20 seconds to receive the full benefit of handwashing with regular soap and water.

Infants and other people with a weakened immune system should not be exposed to reptiles, birds, or amphibians, because these animals typically carry Salmonella bacteria, and infection is more severe in these groups of people.

Because most infections that cause gastroenteritis are transmitted by person-to-person contact, particularly through direct or indirect contact with infected stool, good handwashing with soap and water after a bowel movement is the most effective means of prevention. To prevent foodborne 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 high-risk foods and beverages, such as those sold by street vendors.

To prevent recreational water illness, people should not swim if they have diarrhea. Infants and toddlers should have frequent diaper checks and should be changed in a bathroom and not near the water. Swimmers should avoid swallowing water while swimming.

Because use of most antibiotics can increase the risk of diarrhea caused by Clostridium difficile infection, antibiotics are used only when necessary and never in situations in which they will have no effect (for example, for a viral infection).

Treatment of Gastroenteritis

  • Fluids and rehydration solutions

  • Sometimes drugs

  • Possibly probiotics

Rehydration

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, fluids and electrolytes given by vein (intravenously) 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 (called oral rehydration solutions Treatment Dehydration is loss of water from the body, usually caused by vomiting and/or diarrhea. Dehydration occurs when there is significant loss of body water and, to varying amounts, electrolytes... read more ) are satisfactory. Carbonated beverages, teas, sports drinks, beverages containing caffeine, and fruit juices are not appropriate. If the child is breastfed, breastfeeding Breastfeeding Breast milk is the ideal food for newborns. Although babies may be fed breast milk or formula, doctors recommend exclusive breastfeeding for at least the first 6 months and introducing appropriate... read more Breastfeeding should continue.

As the symptoms subside, the person may gradually add foods to the diet. There is no need to limit the diet to bland foods such as cereal, gelatin, bananas, rice, applesauce, and toast. However, some people are unable to tolerate milk products for a few days after having diarrhea.

Drugs

A doctor may give antinausea drugs by mouth for mild to moderate vomiting. If vomiting is severe, antinausea drugs may be given as an injection or suppository.

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. These drugs usually are not given to children under the age of 2.

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. Antibiotics are also used to treat diarrhea caused by Clostridium difficile. The antibiotic that is used for treatment is different from the antibiotic that caused the Clostridium difficile infection.

Did You Know...

  • Antibiotics do not always help diarrhea that is caused by bacteria.

Parasitic infections are treated with antiparasitic drugs such as metronidazole and nitazoxanide.

Probiotics

Some bacteria are naturally found in the body and promote the growth of good bacteria (probiotics). The use of probiotics, such as lactobacillus (typically present in yogurt), may slightly shorten the duration of diarrhea (perhaps by less than a day). However, probiotics probably do not prevent more serious consequences of gastroenteritis, such as the need for intravenous fluids or for hospitalization.

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