Gastroenteritis Diagnosis

  • Diagnosis

    Gastroenteritis, often called the "stomach flu," is a common and normally short-lived illness characterized by diarrhea and low-grade fever, cramps, nausea, and vomiting. Most people don't require medical attention, although infants, young children, and the elderly are at higher risk for more severe disease. Gastroenteritis, or "stomach flu," is not actually caused by an influenza virus, but by other viruses, as well as many bacteria and parasites. Viral gastroenteritis is easily spread through the fecal-oral route; that is, by ingesting microscopic amounts of contaminated feces. This usually occurs because of inadequate washing after using the bathroom or diapering a baby. Bacterial gastroenteritis, also called food poisoning, is commonly caused by eating food that has spoiled or been contaminated, and often by uncooked meat (for example, steak tartar, which is a raw meat dish) or by eating meat that is cooked rare. Unclean water is another source of transmission of gastroenteritis-causing organisms.

    Gastroenteritis is very common and often occurs in epidemics, either by spreading from person to person in an institution or from many people eating a common contaminated food source. Travelers to countries with poor sanitation are also at high risk for developing gastroenteritis, or "traveler's diarrhea."

    Typically within one to two days of exposure, gastroenteritis causes diarrhea and often low-grade fever, cramps, nausea, and vomiting. Illness typically lasts a few days, with complete recovery in about a week.

    While deaths are rare in developed countries, gastroenteritis is a leading cause of mortality of infants and young children in countries where sanitation is poor.

    Gastroenteritis is most commonly caused by viruses, which are spread by the fecal-oral route.

    A variety of viruses can cause gastroenteritis. They are usually spread by accidental ingestion of microscopic quantities of infected feces. This commonly occurs in several different ways, usually because of inadequate hand washing after using the bathroom or diapering a baby. Infection is easily spread from an infected person throughout a household, daycare center, or restaurant.

    The viruses that can cause gastroenteritis include rotaviruses, adenoviruses, and astroviruses, Norwalk virus, and a group of Norwalk-like viruses.

    The influenza virus does not cause gastrointestinal symptoms. Some viruses are more active at certain times of year; for example, rotavirus and astrovirus are most common in the winter in the U.S. Some virues are more common in certain age groups. For example, rotavirus is the most common cause of diarrhea in infants and young children, while Norwalk and related viruses affect older children and adults. Bacteria that commonly cause gastroenteritis include various types of E. coli, Salmonella, Shigella, and Campylobacter species, as well as organisms that cause cholera and dysentery. Illness may result from the bacteria themselves, or from toxins that are produced by some bacteria. Some toxins cause intestinal cells to secrete fluid, producing large amounts of watery diarrhea. Others damage the intestinal lining so that blood is visible in the stool. Some bacteria produce proteins that enable themselves to adhere to the intestinal wall and multiply, crowding out the normal beneficial intestinal bacteria.

    Certain parasites found in food and water also cause gastroenteritis. Giardia and amebiasis are two examples of parasitic causes of gastroenteritis. Giardia is often contracted by campers who drink directly from streams. Infected individuals often develop a prolonged course of gastrointestinal symptoms. Amebiasis or amoebic dysentery is also caused by a parasite.

    Gastroenteritis causes diarrhea, nausea, vomiting, stomach cramps and low-grade fever. Symptoms of gastroenteritis usually start one to two days after infection, and last from a few days to a week. The characteristics of the illness vary depending on the organism and the dose. General illness in most cases is mild-to-moderate, but can be life-threatening. Stools may range in character from semi-solid to resembling rice-water. Cramps, nausea, and vomiting, weakness and fatigue, and a low-grade fever (<101°F) may also be present.

    People who eat the food prepared in large institutions and food-preparation facilities are at particular risk for spreading epidemics of gastroenteritis. Child-care centers and nursing homes, where personnel may care for others' bathroom needs and also handle food, are particularly susceptible to the spread of viral gastroenteritis. Places where food is prepared for large numbers of people, such as banquet halls, cruise ships, and college dorms, are also inherently risky environments for the spread of both viral and bacterial disease. An infected worker may handle food for large numbers of people, or large quantities of food may be improperly prepared or left at room temperature for too long.

    Gastroenteritis is usually a mild disease, but tends to be more dangerous for certain groups. One of the biggest risks of gastroenteritis is dehydration. Infants, young children, and the elderly, who are less able to care for their own needs, are particularly at risk for dehydration.

    In addition, some people are more likely to develop infections with more unusual strains, or become sicker from organisms that healthier people are able to fight off more easily. This includes young infants as well as those with weakened immune systems, such as AIDS patients. Individuals with disorders such as diabetes and scleroderma, which slow down the ability of their intestines to flush wastes through, are also more susceptible to disease-causing organisms taking hold in their intestines.

    Some medications—including antacids, antibiotics, opiates, and anti-diarrhea drugs—create an environment conducive to the development of gastroenteritis. Long-term use of antacids and medications such as cimetidine (Tagamet) alter the acid environment of the stomach and colon, which normally provides a defense against many gastroenteritis-causing microorganisms. In addition, magnesium-containing antacids can actually cause diarrhea, mimicking gastroenteritis.

    People who have recently finished a course of antibiotics are also more vulnerable to gastroenteritis.

    Medications that slow the movement of the intestines, including opiates (such as codeine or morphine) and anti-diarrhea drugs, make individuals more susceptible to potentially dangerous organisms that normally quickly pass through the gastrointestinal system.

    Gastroenteritis can usually be diagnosed based on symptoms, a history of exposure, and a physical exam. Your physician will suspect gastroenteritis if you have had a few days of gastrointestinal upset. Information about exposure to people with similar symptoms at home or in the workplace, having recently eaten unusual-tasting or otherwise suspicious food, or having recently been on a camping trip or having traveled outside of the U.S. can help with the diagnosis. The physician will perform a physical exam to rule out urgent problems such as appendicitis, and will check for signs of dehydration.

    Laboratory testing is only occasionally needed. If symptoms are unusually severe or last more than a week, the physician may order lab tests. Stools can be directly examined under the microscope and cultured for various bacteria and parasites.

    Hand washing is the best protection against spreading viral gastroenteritis. Food handlers, health care personnel, and child care workers should be especially thorough in washing hands after using the bathroom, diapering, or handling bedpans. Promptly disinfecting contaminated surfaces using household chlorine bleach—based cleaners is essential in institutional settings. In households where someone is sick, avoid sharing hand towels, and promptly launder any soiled linens.

    Observe safe food-handling procedures to avoid food poisoning, both at home and in group settings. With reasonable care, most food-borne cases of gastroenteritis can be avoided. Take particular precautions with foods that have the greatest danger of spoiling, including meat, seafood, mayonnaise, eggs, and milk products, especially when preparing picnics or large events.

    • Wash hands before handling food and after touching meat, fish, or eggs.
    • Keep work areas clean. Never use cutting surfaces, plates, or utensils that have touched raw meat for anything else until thoroughly washed.
    • Cook meat thoroughly. Never partially cook meat, then leave to reheat later.
    • Keep food in coolers for as long as possible at picnics. Foods kept out at room temperature for longer than two hours should be discarded.
    • Throw out any food that you are unsure about.

    For further information about the safe cooking and handling of foods, call USDA's Meat and Poultry Hotline at (800) 535-4555.

    Take precautions when going to a less-developed country or on a camping trip. Before traveling to another country, find out if the water is safe to drink. If not, drink only bottled or boiled water. While hot foods should be safe, avoid uncooked vegetables or fruits that you have not peeled yourself. High-risk individuals who travel to underdeveloped countries may wish to take antibiotics as a precaution against gastroenteritis. These include people with AIDS, inflammatory bowel disease, or those who regularly use insulin (to control diabetes, for example) or a medication like cimetidine (Tagamet), which alters the acid environment of the stomach.

    Before wilderness camping, learn about various water-purification methods that are available. These include filtration devices or tablets that can be added to water. Do not assume that clear mountain streams are safe.

  • Prevention and Screening

    Hand washing is the best protection against spreading viral gastroenteritis. Food handlers, health care personnel, and child care workers should be especially thorough in washing hands after using the bathroom, diapering, or handling bedpans. Promptly disinfecting contaminated surfaces using household chlorine bleach—based cleaners is essential in institutional settings. In households where someone is sick, avoid sharing hand towels, and promptly launder any soiled linens.

    Observe safe food-handling procedures to avoid food poisoning, both at home and in group settings. With reasonable care, most food-borne cases of gastroenteritis can be avoided. Take particular precautions with foods that have the greatest danger of spoiling, including meat, seafood, mayonnaise, eggs, and milk products, especially when preparing picnics or large events.

    • Wash hands before handling food and after touching meat, fish, or eggs.
    • Keep work areas clean. Never use cutting surfaces, plates, or utensils that have touched raw meat for anything else until thoroughly washed.
    • Cook meat thoroughly. Never partially cook meat, then leave to reheat later.
    • Keep food in coolers for as long as possible at picnics. Foods kept out at room temperature for longer than two hours should be discarded.
    • Throw out any food that you are unsure about.

    For further information about the safe cooking and handling of foods, call USDA's Meat and Poultry Hotline at (800) 535-4555.

    Take precautions when going to a less-developed country or on a camping trip. Before traveling to another country, find out if the water is safe to drink. If not, drink only bottled or boiled water. While hot foods should be safe, avoid uncooked vegetables or fruits that you have not peeled yourself. High-risk individuals who travel to underdeveloped countries may wish to take antibiotics as a precaution against gastroenteritis. These include people with AIDS, inflammatory bowel disease, or those who regularly use insulin (to control diabetes, for example) or a medication like cimetidine (Tagamet), which alters the acid environment of the stomach.

    Before wilderness camping, learn about various water-purification methods that are available. These include filtration devices or tablets that can be added to water. Do not assume that clear mountain streams are safe.

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