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Gastroenteritis describes a group of conditions
usually caused by infection with a microorganism or ingestion
of chemical toxins.
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
and electrolyte imbalance in the very ill, the very young,
and the very old.
Causes
Infections that produce gastroenteritis can be transmitted
from person to person, especially if someone with diarrhea
does not thoroughly wash his hands after a bowel movement.
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.
Certain bacteria produce toxins that cause the cells in the
intestinal wall to secrete electrolytes and water. One such
toxin, produced by the bacterium Vibrio cholerae,
is responsible for the watery diarrhea that is the main symptom
of cholera; other Vibrio species, often present in
raw shellfish, produce a similar but less severe gastroenteritis.
A toxin produced by the common bacterium Escherichia coli
(E. coli) may cause traveler's diarrhea and some outbreaks
of diarrhea in hospital nurseries.
Some bacteria (such as certain strains of E. coli,
Campylobacter, Shigella, and Salmonella)
invade the lining of the intestine. There, they damage cells,
causing tiny sores (ulcerations) that bleed and allow a considerable
leakage of fluid containing proteins, electrolytes, and water.
Besides bacteria, several types of viruses, such as rotaviruses
and the Norwalk virus, cause gastroenteritis. During the winter
in temperate climates, rotaviruses cause most cases of diarrhea
that are serious enough to send infants and toddlers to the
hospital.
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. Another intestinal parasite,
called Cryptosporidium, causes watery diarrhea that
is sometimes accompanied by abdominal cramps, nausea, and
vomiting. The resulting infection, called cryptosporidiosis,
is usually mild in otherwise healthy people, but it may be
severe or even fatal in people with a weakened immune system.
Both Giardia and Cryptosporidium are most
commonly acquired by drinking contaminated water.
Gastroenteritis may result from eating 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. Eating large amounts of acidic foods, such as
citrus fruits and tomatoes, gives some people a chemical-induced
gastroenteritis.
Symptoms
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 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.
Diagnosis
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 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, 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. In rare cases,
laboratory analysis of vomit, food, or blood may help identify
the cause.
If the symptoms persist beyond a few days, a doctor may need
to examine the large intestine with a colonoscope (a flexible
viewing tube) to determine whether the person has a disease
such as ulcerative colitis.
Prevention and Treatment
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, 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. For infants,
a simple and effective way to prevent gastroenteritis is breastfeeding.
Usually the only treatment needed for gastroenteritis is
to drink 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. For adults, a doctor may give
a drug, either as an injection or as a suppository, to control
severe vomiting. These drugs usually are not given to young
children.
As the symptoms subside, the person may gradually add bland
foods--such as cooked cereals, bananas, rice, applesauce,
and toast--to the diet. If the diarrhea continues after following
the bland diet for 12 to 24 hours and there is no blood in
the stool to indicate a more serious bacterial infection,
the doctor may prescribe a drug such as diphenoxylate or instruct
the person to use an over-the-counter drug such as loperamide
or bismuth subsalicylate. Again, these drugs usually are not
given to young children.
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.
Hemorrhagic Colitis
Hemorrhagic colitis is a type of gastroenteritis
in which certain strains of the bacterium Escherichia coli
(E. coli) infect the large intestine and produce a toxin that
causes bloody diarrhea and other serious complications.
Hemorrhagic colitis can occur in people of all ages but is
most common in children and older people. In North America,
the most common strain of E. coli that causes hemorrhagic
colitis is found in the intestines of healthy cattle. Outbreaks
can be caused by eating undercooked beef, especially ground
beef, or by drinking unpasteurized milk. Unpasteurized juice
can also be contaminated. The disease can be transmitted from
person to person, particularly among children in diapers.
E. coli toxins damage the lining of the large intestine.
If they are absorbed into the bloodstream, they can also affect
other organs, such as the kidney.
Symptoms
Severe abdominal cramps begin suddenly along with watery diarrhea,
which typically becomes bloody within 24 hours. The diarrhea
usually lasts 1 to 8 days. Fever is usually absent or mild
but occasionally can exceed 102° F (38.9° C).
About 5% of people with hemorrhagic colitis develop a severe
complication called hemolytic-uremic syndrome. Symptoms include
anemia (characterized by fatigue, weakness, and light-headedness)
caused by the destruction of red blood cells (hemolytic anemia),
a low platelet count (thrombocytopenia), and sudden kidney
failure. Some people with hemolytic-uremic syndrome also develop
complications of nerve or brain damage, such as seizures or
strokes. These complications typically develop in the second
week of illness and may be preceded by increasing fever. Hemolytic-uremic
syndrome is more likely to occur in children younger than
5 years and in older people. Even without hemolytic-uremic
syndrome and its complications, hemorrhagic colitis may cause
death in older people.
Diagnosis and Treatment
A doctor usually suspects hemorrhagic colitis when a person
reports bloody diarrhea. To make the diagnosis, a doctor has
stool specimens tested for strains of E. coli. Other
tests, such as colonoscopy, may be performed if a doctor suspects
that other diseases may be causing the bloody diarrhea.
The most important aspect of treatment is drinking enough
fluids. Sometimes so much fluid is lost, however, that a doctor
has to replace them intravenously. The diet is kept bland,
with cooked cereals, bananas, rice, applesauce, and toast.
Antibiotics are not given because they increase the risk of
developing hemolytic-uremic syndrome. People who develop complications
are likely to require intensive care in the hospital and may
need kidney dialysis.
Staphylococcal Food
Poisoning
Staphylococcal food poisoning results from
eating food contaminated with toxins produced by certain types
of staphylococci, resulting in diarrhea and vomiting.
The staphylococci bacteria grow in food, in which they produce
their toxins. Thus, staphylococcal food poisoning does not
result from ingesting the bacteria but rather from ingesting
the toxins that are already present in the contaminated food.
Typical contaminated foods include custard, cream-filled pastry,
milk, processed meats, and fish. The risk of an outbreak is
high when food handlers with skin infections contaminate foods
left at room temperature.
Symptoms and Diagnosis
Symptoms usually begin abruptly with severe nausea and vomiting
starting about 2 to 8 hours after the contaminated food is
eaten. Other symptoms may include abdominal cramping, diarrhea,
and sometimes headache and fever. Severe fluid and electrolyte
loss may cause weakness and very low blood pressure (shock).
Symptoms usually last less than 12 hours, and recovery is
usually complete. Occasionally, staphylococcal food poisoning
is fatal, especially in the very young, the very old, and
people weakened by long-term illness.
The symptoms are usually all a doctor needs to make the diagnosis
of gastroenteritis. A more specific diagnosis of staphylococcal
food poisoning may be suspected when other people who ate
the same food are similarly affected and when the disorder
can be traced to a single source of contamination. To confirm
the diagnosis, a laboratory analysis must identify staphylococci
in the suspected food, but this analysis is not usually performed.
Microscopic specimens of vomit may also show staphylococci.
Prevention and Treatment
Careful food preparation can prevent staphylococcal food poisoning.
Anyone who has a skin infection should not prepare food for
others until the infection heals.
Treatment usually consists of only drinking an adequate amount
of fluids. A doctor may give a drug, either as an injection
or as a suppository, to help control severe nausea and vomiting.
Sometimes so much fluid is lost that fluids have to be given
intravenously.
Clostridium perfringens
Food Poisoning
Clostridium perfringens food poisoning results
from eating food contaminated by the bacterium Clostridium
perfringens; once in the small intestine, the bacterium releases
a toxin that often causes diarrhea.
Some strains cause a mild to moderate disease that gets better
without treatment; other strains cause severe gastroenteritis
that can damage the small intestine and sometimes lead to
death. Contaminated meat is usually responsible for outbreaks
of Clostridium perfringens food poisoning. Some strains
cannot be destroyed by cooking the food thoroughly; others
can.
Symptoms, Diagnosis, and Treatment
The gastroenteritis is usually mild, although it can cause
abdominal pain, abdominal expansion (distention) from gas,
severe diarrhea, dehydration, and a severe decrease in blood
pressure (shock). A doctor usually suspects the diagnosis
when a local outbreak of the disease has occurred. The diagnosis
is confirmed by testing contaminated food for Clostridium
perfringens. The person is given fluids and is encouraged
to rest.
Traveler's Diarrhea
Traveler's diarrhea (turista) is characterized
by diarrhea, nausea, and vomiting that commonly occur in travelers
to areas of the world with poor water purification.
Traveler's diarrhea occurs when people are exposed to bacteria
in food and water to which they have had little exposure and
thus no immunity. It occurs mostly in developing countries
where the water supply is inadequately treated. The organisms
most likely to cause traveler's diarrhea are the types of
Escherichia coli (E. coli) that produce certain
toxins and some viruses such as the Norwalk virus.
Symptoms and Diagnosis
Nausea, vomiting, intestinal rumbling, abdominal cramping,
and diarrhea can occur in any combination and with any degree
of severity. Vomiting, headache, and muscle pain are particularly
common in infections caused by the Norwalk virus. Most cases
are mild and disappear without treatment within 3 to 5 days.
Diagnostic tests are rarely needed.
Prevention and Treatment
Travelers should patronize only those restaurants with a reputation
for safety and should not purchase any food or beverages from
street vendors. Cooked foods that are still hot when served
are generally safe. Salads containing uncooked vegetables
should be avoided, and all fruit should be peeled by the traveler.
Travelers should drink only bottled carbonated beverages or
beverages made with water that has been boiled. Even ice cubes
should be made with water that has been boiled.
Preventive antibiotics are recommended only for people who
are particularly susceptible to the consequences of traveler's
diarrhea, such as those whose immune system is impaired. The
antibiotic most commonly recommended is ciprofloxacin. Bismuth
subsalicylate, a nonprescription drug, can help.
When symptoms occur, treatment includes drinking plenty of
fluids and eating a bland diet (for example, cooked cereals,
bananas, rice, applesauce, and toast). In addition, antibiotics
(such as ciprofloxacin) and antidiarrheal drugs (such as loperamide
or bismuth) are usually recommended. Travelers are encouraged
to seek medical care if they develop fever or blood in the
stool.
Chemical Food Poisoning
Chemical food poisoning results from eating
a plant or animal that contains a toxin.
Mushroom (Toadstool) Poisoning: Mushroom
poisoning can result from ingesting any of several species
of mushroom. The potential for poisoning may vary within the
same species, at different times of the growing season, and
with cooking. In poisoning caused by many species of Inocybe
and some species of Clitocybe, the dangerous substance
is muscarine. Symptoms, which begin a few minutes to 2 hours
after eating, may include increased tearing and salivation,
narrowing (constriction) of the pupils, sweating, vomiting,
stomach cramps, diarrhea, dizziness, confusion, coma, and
occasionally, seizures. With appropriate treatment, the person
usually recovers in 24 hours. Without treatment, death can
occur in a few hours.
In phalloidine poisoning, caused by eating Amanita phalloides
and related species of mushroom, symptoms start in 6 to 24
hours. People develop intestinal symptoms similar to those
of muscarine poisoning, and kidney damage may reduce or stop
urination. Jaundice from liver damage is common and develops
in 2 or 3 days. Sometimes the symptoms disappear on their
own, but about half of the people who have phalloidine poisoning
die in 5 to 8 days.
Plant and Shrub Poisoning: This type of
poisoning can result from ingesting the leaves and fruits
of many wild and domestic plants and shrubs. Green or sprouting
underground roots that contain solanine may produce mild nausea,
vomiting, diarrhea, and weakness. Fruit of the Koenig tree
causes the vomiting sickness of Jamaica.
Seafood Poisoning: Gastroenteritis may be
caused by eating bony fish or shellfish. Usually, poisoning
caused by eating bony fish results from one of three toxins--ciguatera,
tetraodon, or histamine.
Ciguatera poisoning can occur after eating
any of more than 400 species of fish from the tropical reefs
of Florida, the West Indies, or the Pacific. The toxin is
produced by certain dinoflagellates, microscopic sea organisms
that the fish eat and that accumulate in their flesh. Larger,
older fish are more toxic than smaller, younger ones. The
flavor of the fish is not affected. Current processing procedures
cannot destroy the toxin. The initial symptoms--abdominal
cramps, nausea, vomiting, and diarrhea--may begin 2 to 8 hours
after the person eats the fish and last 6 to 17 hours. Later
symptoms may include itchiness, a pins-and-needles sensation,
headache, muscle aches, a reversal of sensations of hot and
cold, and facial pain. For months afterward, the sensations
may be disabling.
Tetraodon poisoning from the puffer fish,
which is found most commonly in the seas surrounding Japan,
is similar to ciguatera poisoning. Death may result from paralysis
of the muscles that regulate breathing.
Histamine poisoning from fish such as mackerel,
tuna, and blue dolphin (mahimahi) occurs when the tissues
of the fish break down after it has been caught, producing
high levels of histamine. When ingested, histamine causes
immediate facial flushing. It can also cause nausea, vomiting,
stomach pain, and hives (urticaria) a few minutes after a
person eats the fish. Symptoms usually last less than 24 hours.
Neurotoxin poisoning can occur from June
to October, especially on the Pacific and New England coasts.
Shellfish such as mussels, clams, oysters, and scallops may
ingest certain poisonous dinoflagellates at certain times
when the water has a red cast, called the red tide. They produce
a toxin that attacks nerves (such toxins are called neurotoxins).
The toxin, which produces paralytic shellfish poisoning, persists
even after the food has been cooked. The first symptom, a
pins-and-needles sensation around the mouth, begins 5 to 30
minutes after eating. Nausea, vomiting, and abdominal cramps
develop next. About 25% of people develop muscle weakness
over the next few hours; occasionally, the weakness progresses
to paralysis of the arms and legs. Weakness of the muscles
needed for breathing may even be severe enough to cause death.
Contaminant Poisoning: Gastroenteritis may
affect people who have ingested unwashed fruits and vegetables
sprayed with arsenic, lead, or organic insecticides; acidic
fluids served in lead-glazed pottery; or food stored in cadmium-lined
containers.
Treatment
Most people with chemical food poisoning recover fully and
rapidly with nothing more than replacement of fluids and electrolytes.
As soon as symptoms begin, a person should try to consume
large amounts of fluids. If fluids cannot be tolerated, the
person needs to go to an emergency room for intravenous fluid
replacement.
If possible, it is often a good idea to rid the stomach of
the toxic substance as quickly as possible. For most people,
vomiting accomplishes this. Saving a small amount of the first
vomitus may be useful if tests are needed later. If a person
cannot vomit adequately and symptoms are severe, a doctor
may empty the stomach by placing a small tube through the
nose or mouth into the stomach. A laxative helps to pass the
toxins from the intestines more quickly.
Specific treatments are sometimes given when the toxin is
known. For example, atropine is given for certain types of
mushroom poisoning. Phalloidine poisoning is treated with
a diet high in carbohydrates and sugar given intravenously.
Ciguatera poisoning is sometimes treated with mannitol given
intravenously. Antihistamines help block the symptoms of histamine
poisoning.
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