Gastroenteritis is an inflammation or irritation of the lining of the stomach and intestines, which often results in diarrhea, nausea, vomiting or stomach cramps.

In healthy adults, gastroenteritis is not usually a serious condition. However, the condition can cause life-threatening dehydration or electrolyte imbalance in infants and children, or in adults who are unable to care for themselves. People with other medical conditions or weakened immune systems may be at risk for developing severe gastroenteritis.

Gastroenteritis is most often caused by viruses spread by close contact with an infected person, or by consuming food contaminated by bacteria. The condition can also be caused by parasites, protozoans, chemicals or toxins. Certain types of medications may also cause the condition.  

Gastroenteritis may be diagnosed during a physical examination that includes a medical history. If patients have been experiencing symptoms for 48 hours or longer, physicians may request a stool sample, which will be put in a culture medium and bacteria and protozoa that may be causing the illness will grow and will be characterized in a lab. Viruses are usually detected by a culture. In many cases, people with gastroenteritis recover after several days without seeing a physician.

Mild cases of gastroenteritis may be treated at home by increasing fluid intake to avoid dehydration. This is particularly important for children, who usually become dehydrated faster than adults. More severe cases may require hospitalization and intravenous administration of fluids.

Gastroenteritis may be prevented in a variety of ways. Washing hands thoroughly can help prevent spread of infection. Cooking meat and eggs properly and making sure food is refrigerated at an appropriate temperature can help prevent contamination of food.

Gastroenteritis is a general term to describe a variety of infectious conditions that result in irritation or inflammation of the stomach and small and large intestines.

The primary symptom of gastroenteritis is diarrhea, which occurs when the intestines secrete and/or are unable to reabsorb fluid. This can result from damage to the cells lining the intestines, which can have numerous infectious and noninfectious causes.

As a result, stools contain more water, causing them to become watery and runny. Other symptoms and complications of gastroenteritis (e.g., dehydration) are often related to diarrhea.

In healthy adults, gastroenteritis is not usually a serious condition, and recovery typically occurs after several days with no lasting problems. However, in very young people, unhealthy adults and those with weakened immune systems, gastroenteritis can cause dehydration and imbalance of electrolytes (chemicals necessary for normal bodily function).

A physician should be consulted if:

• Symptoms persist for longer than 36 hours
• Blood is present in diarrhea or vomit
• Patients have a fever of 103 degrees Fahrenheit (39.4 degrees Celsius) or higher
• Patients feel lightheaded or faint after standing
• Patients become unusually drowsy or confused
• Abdominal pains are severe
• Patients show signs of dehydration

Eosinophilic gastroenteritis is a rare disease in which the lining of the stomach and the large and small intestines become infiltrated with a type of white blood cell called eosinophils. Unlike other types of gastroenteritis, it can involve any part of the gastrointestinal tract from the esophagus to the rectum.

Viral infection is one of the most common causes of gastroenteritis. The condition is often called “stomach flu,” but it is not actually caused by an influenza virus (which is an upper respiratory disease).

Viruses are typically spread through person-to-person contact, although they can also be spread through contaminated food and water. A number of different viruses can cause gastroenteritis, including:

• Rotavirus. Leading cause of gastroenteritis in children ages 3 months to 15 months old. It can also affect adults who come into close contact with children, but produces milder symptoms in adults. Infections usually occur during the winter.
  
  
• Calicivirus. Causes infection in people of all ages. Caliciviruses are divided into noroviruses and sapoviruses. Epidemics (when a large group of people are infected at the same time or from the same source) are usually caused by caliciviruses.
  
  
• Adenovirus. Causes gastroenteritis in children younger than age 2. Symptoms usually appear one week after exposure. Infections occur year-round.
  
  
• Astrovirus. Causes infection primarily in infants, young children and the elderly. Infections usually occur during the winter months.

Most bacteria that cause gastroenteritis are spread through contaminated food. Improper food handling and undercooked food are common causes of bacterial infection.

The most common types of bacteria that cause gastroenteritis include:

• Campylobacter. The most commonly identified bacterial cause of diarrheal illness in the world. The bacteria live in the intestines of healthy birds.
  
  
• Salmonella. Found in the intestines of birds, reptiles and mammals.
  
  
• Escherichia coli (E. coli). Bacterial pathogen found in cattle and similar animals. Illness typically occurs after consumption of food or water that has been contaminated with microscopic amounts of cow feces.
  
  
• Staphylococcus aureus. Unlike other types of foodborne illness, this is not caused by contamination. This bacterium can grow in some foods and produce a toxin that results in intense vomiting.

Parasites and protozoans can cause gastroenteritis by consuming contaminated water and food. They can also be spread through contact with contaminated surfaces, toys and other objects, or by swimming in water infected by these organisms.

• Giardia lamblia. Parasite that invades the lining of the intestine and causes symptoms, such as nausea, vomiting and diarrhea. It is more common in cold climates, but can occur in any climate.
  
  
• Cryptosporidia. Causes watery diarrhea that is sometimes accompanied by abdominal cramps, nausea and vomiting. The infection is usually mild in healthy people, but can be severe or fatal in people with weakened immune systems.

Some types of foods, such as shellfish and certain species of mushrooms, contain chemicals or toxins that result in illness when eaten. Most cases result in mild symptoms, but some are more serious and require immediate medical treatment.

In addition, there are many medications that can cause gastroenteritis (drug-related gastroenteritis) and small intestinal inflammation. For example, antibiotics can alter the normal amount and type of bacteria found in the large intestine and allow the bacterium clostridium difficile to grow and cause diarrhea. Other medications, such as antacids, laxatives, aspirin and nonsteroidal anti-inflammatory drugs (NSAIDs) can irritate the stomach.

People at greater risk of developing gastroenteritis include:

• Elderly people. As people age, their immune systems do not respond as quickly and effectively to infectious organisms.
  
  
• Infants and young children. The immune systems of very young people are not fully developed.
  
  
• People with weakened immune systems. People with certain medical conditions, such as human immunodeficiency virus (HIV) or diabetes, have a greater risk.
  
  
• Pregnant women. Pregnant women are at greater of getting gastroenteritis.

Signs and symptoms of gastroenteritis vary among individuals and depend upon the type and quantity of the pathogen (disease-causing organism). Symptoms may appear within hours or days of being infected. They usually last from one to two days but may last 10 days or longer. Diarrhea is the most common symptom. Other symptoms include:

• Loss of appetite
• Nausea
• Vomiting
• Abdominal cramping
• Audible rumbling of intestines
• Malaise (general sick feeling)
• Fever
• Aching muscles
• Exhaustion

Patients who experience severe vomiting and diarrhea due to gastroenteritis may also experience the following signs and symptoms:

• Dehydration, including excessive thirst, weakness, lightheadedness, decreased frequency of urination, dry mouth or lack of tears in infants
  
  
• Low levels of potassium in the blood (hypokalemia)
  
  
• Low levels of sodium in the blood (hyponatremia)
  
  
• Imbalances of water or electrolytes (chemicals needed for normal bodily function)

Most cases of gastroenteritis do not require a visit to a physician. However, a physician should be consulted if:

• Symptoms persist for longer than 36 hours
• Blood is present in diarrhea or vomit
• Patients have a fever of 103 degrees Fahrenheit (39.4 degrees Celsius) or higher
• Patients feel lightheaded or faint after standing
• Patient becomes unusually drowsy or confused
• Abdominal pains are severe
• Patients show signs of dehydration

Gastroenteritis may be diagnosed by a physician during a physical examination that includes a medical history and list of medications. Patients are typically asked to describe the type and duration of symptoms experienced, such as diarrhea, nausea, vomiting and/or abdominal cramping. However, many people (particularly adults) do not consult a physician for mild cases of gastroenteritis.

Other information that patients may be asked to provide includes:

• Foods consumed in the past few days
  
  
• Recent travel, especially to foreign countries (which can result in a condition known as traveler’s diarrhea)
  
  
• Changes in medications
  
  
• Friends and/or family members who are experiencing similar symptoms

Physicians may examine the abdomen for the presence of tenderness or masses, which sometimes indicate the presence of another underlying condition, such as appendicitis (inflammation of the appendix) or cholecystitis (inflammation of the gallbladder).

There is no specific test to diagnose gastroenteritis. If patients have been experiencing symptoms for 48 hours or longer, physicians may request a stool sample, which will be examined in a laboratory under a microscope after being put in a culture medium to detect the presence of bacteria, parasites or other microorganisms that may be causing the illness. Gastroenteritis caused by a rotavirus infection can be diagnosed with a stool test. Most cases of viral gastroenteritis are not diagnosed because symptoms are usually mild and are not seen by a physician.

If symptoms last for longer than a few days, a physician may perform a colonoscopy (an examination of the inside of the colon). This test will help determine whether a condition other than gastroenteritis, such as ulcerative colitis  (chronic inflammation of the colon that produces ulcers in its lining), is causing symptoms.

Treatment for gastroenteritis varies according to the type and severity of the illness. Most cases resolve on their own within several days. Mild cases may be treated by replacing fluids and electrolytes (chemicals needed for normal body function) to prevent dehydration. Increasing fluid intake is particularly important for children because they become dehydrated faster than adults. Diarrhea that is caused by medications (e.g., antacids, antibiotics) is treated by stopping the drug.

Tips for replacing fluids include:

• Begin by drinking small amounts of clear liquids (4 or more ounces each hour) as tolerated. Soft drinks, tea, coffee, fruit juice and sports drinks should be avoided because they do not replace electrolytes appropriately.
  
  
• Drink plenty of oral rehydration solutions (liquids with glucose and electrolytes designed to replace fluids lost due to diarrhea) if diarrhea is severe. This is especially important for children. 
  
  
• Take antidiarrheal medications to ease symptoms of diarrhea. However, these medications should be avoided by children and patients experiencing a high fever or blood in the stools. Also, these medications should not be taken more than three days unless directed by a physician.

After vomiting subsides, patients may start to gradually eat solid foods. Some diet tips include:

• Eat foods that contain salt, such as crackers or pretzels, to replace lost sodium.
  
  
• Eat foods such as oatmeal, white rice, applesauce and bananas to help slow down bowel movements.
  
  
• Eat foods that are easy to digest, such as broth or chicken soup.
  
  
• Do not eat or drink foods and beverages, such as chewing gum and apple juice, that contain sorbitol, a sugar alcohol that worsens diarrhea.
  
  
• Limit intake of dairy products, fatty and greasy foods (e.g., pizza) and high-fiber foods (e.g., bran cereal, whole-grain breads) because they may worsen diarrhea.

Cases of gastroenteritis that cause severe dehydration may require hospitalization. Patients may receive fluids intravenously (through a vein). Patients may be given antidiarrheal medications to ease diarrhea or antiemetics to treat nausea and/or vomiting. Although antiemetics are not typically administered to children, research shows that one such drug may be effective in treating youngsters with gastroenteritis.

Patients are rarely given antibiotics to treat a bacterial infection. There are only a few types of gastroenteritis (such as shigellosis) that require antibiotic treatment. In fact, antibiotics can cause gastrointestinal infections in some people. Patients who have eaten foods contaminated with pesticides or other types of toxins may have their stomachs pumped (lavage) to remove the contents.

Researchers are also currently working to develop new treatments for gastroenteritis. For example, a molecule in coral has proven effective in fighting the virus that causes gastroenteritis, which may prove promising in the development of improved treatments.

There are a variety of ways to prevent gastroenteritis. Washing hands thoroughly, especially before eating and after a bowel movement, will help prevent the transmission of viral gastroenteritis (which is spread from person to person). Soiled clothing should be washed with detergent and bleach.

There are numerous ways to prevent gastroenteritis that is spread through contaminated food. They include:

• Store food that spoils easily, such as meat and dairy products, in the freezer or the coldest parts of the refrigerator.
  
  
• Wash hands both before and after preparing food.
  
  
• Use separate cutting boards for meat and vegetables when preparing food.
  
  
• Meat, poultry and eggs should be cooked properly before eating. Leftovers should be wrapped and stored in the refrigerator within two hours.
  
  
• When traveling to areas with poor sanitation, drink only  bottled water or carbonated soft drinks and avoid using ice in beverages.
  
  
• Exercise caution when using public spas, swimming pools and other recreational bathing facilities, which may harbor parasites and protozoans that can cause gastroenteritis. The World Health Organization recently launched the first international guidelines on how to create safe facilities for bathing and swimming.
  

Research continues into additional ways to treat and prevent gastroenteritis. For example, the U.S. Food and Drug Administration recently approved a new vaccine to prevent rotavirus gastroenteritis in infants.

Preparing questions in advance can help patients to have more meaningful discussions with their physicians regarding their conditions. Patients may wish to ask their doctor the following gastroenteritis-related questions:

1. What is gastroenteritis?
   
   
2. What is the difference between gastroenteritis and the stomach flu?
   
   
3. Is gastroenteritis more serious in children than in adults?
   
   
4. Is a physical exam necessary if I suspect I have gastroenteritis?
   
   
5. How may I have contracted my case of gastroenteritis?
   
   
6. What is the best way to treat my gastroenteritis?
   
   
7. Are there any foods that I should avoid until my gastroenteritis is cured?
   
   
8. For how long do you suspect my gastroenteritis will last?
   
   
9. Should my children receive special treatment for gastroenteritis?
   
   
10. What is the best way to prevent gastroenteritis?