Muhtasari wa Gastroenteraitisi

Viruses 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 types of viruses cause gastroenteritis: norovirus, rotavirus, astrovirus, and enteric (intestinal) adenovirus.

Most viral gastroenteritis infections are caused by

• Norovirus

• Rotavirus

Astrovirus can infect people of all ages but usually infects infants and young children. In temperate climates, infection is most common during winter months. In tropical climates, infection is more common during summer months. It is spread by fecal-oral transmission. Symptoms start 3 to 4 days after infection.

Adenovirus is the 4th most common cause of childhood viral gastroenteritis. It 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 and in respiratory droplets of moisture such as those produced by coughing. Anyone nearby may inhale these droplets and become infected. Symptoms start 3 to 10 days after infection.

Other viruses (such as cytomegalovirus and enterovirus) can cause gastroenteritis in people who have an impaired immune system.

The most common bacterial causes of gastroenteritis are

• Campylobacter

• Clostridioides difficile (C. diff)

• Escherichia coli (E. coli), especially strain O157:H7

• Salmonella

• Shigella

• Staphylococci, causing staphylococcal food poisoning

Bacterial gastroenteritis is less common than viral gastroenteritis. Bacteria cause gastroenteritis by various means.

Certain species, such as Vibrio cholerae and enterotoxigenic strains of E. coli, attach to the lining of the intestines without invading and produce enterotoxins. These toxins cause the intestines to secrete water and electrolytes, resulting in watery diarrhea.

Other bacteria (such as Staphylococcus aureus [see also Staphylococcal Food Poisoning], Bacillus cereus, and Clostridium perfringens) produce an exotoxin that can be present in contaminated food. The toxin can cause gastroenteritis without causing a bacterial infection. These toxins generally cause severe nausea, vomiting, and diarrhea. Symptoms begin within 12 hours of ingesting contaminated food and lessen within 36 hours.

Some bacteria (such as certain strains of E. coli, Campylobacter, Shigella, Salmonella, and Clostridioides difficile) invade the lining of the small or large intestine (colon). There, they damage cells, causing sores (ulcerations) that bleed, and allow a considerable leakage of fluid containing proteins, electrolytes, and water. The diarrhea contains microscopic 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.

E. coli gastroenteritis can be caused by several different subtypes of the bacteria.

Clostridioides difficile (C. diff) 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 Drug-Related Gastroenteritis). 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 Clostridioides difficile bacteria to grow in their place. Clostridioides difficile produces a toxin that causes watery diarrhea that ranges from mild to severe and bloody (see also Clostridioides difficile–induced diarrhea).

Several other bacteria cause gastroenteritis, but most are rare in the United States. Yersinia enterocolitica can cause gastroenteritis or a syndrome that mimics appendicitis. A person is infected after ingesting undercooked pork, unpasteurized milk, or contaminated water. Several Vibrio species (such as Vibrio parahaemolyticus) cause diarrhea after ingesting undercooked seafood. Vibrio cholerae, which causes cholera, is responsible for the watery diarrhea that sometimes causes severe dehydration in people in low-resource countries. Epidemics may occur after natural disasters or in refugee camps. Listeria can rarely cause foodborne gastroenteritis but more often causes a bloodstream infection or meningitis in pregnant women, newborns, or older adults. 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 low-resource countries.

The most common parasites are

• Giardia

• Cryptosporidium

Certain intestinal parasites, particularly Giardia intestinalis, stick to the lining of the intestine and cause nausea, vomiting, diarrhea, and a general sick feeling. The resulting infection, called giardiasis, occurs in every region of the United States and throughout the world. If the infection becomes persistent (chronic), it may keep the body from absorbing nutrients (called malabsorption syndrome). Infection is usually spread through drinking contaminated water (sometimes from wells or unconventional water sources encountered while hiking or camping), eating contaminated food, or through 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, 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. Entamoeba histolytica causes amebiasis, an infection of the large intestine and sometimes the liver and other organs. Amebiasis is a common cause of bloody diarrhea in countries where sanitation is inadequate but is rare in the United States.

Viruses cause watery diarrhea. Stools rarely contain mucus or blood. For symptoms specific to norovirus and rotavirus, see Norovirus Gastroenteritis and Rotavirus Gastroenteritis.

Adenovirus causes mild vomiting 1 to 2 days after diarrhea starts. The diarrhea can last 1 to 2 weeks. Infants and children may have mild vomiting that typically starts 1 to 2 days after diarrhea starts. A low fever occurs in about 50% of people. Some people may have nasal congestion, a runny nose, scratchy throat, and cough. Symptoms are typically mild but can last longer than with other viral causes of gastroenteritis.

Astrovirus symptoms are similar to a mild rotavirus infection.

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

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.

Severe vomiting and diarrhea can lead to marked fluid loss (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 electrolyte problems such as low levels of potassium in the blood (hypokalemia) and dehydration, which can cause low blood pressure and a rapid heart rate. 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. Low blood volume (hypovolemic shock) and kidney failure can occur in severe cases.

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) are satisfactory. Carbonated beverages, teas, sports drinks, beverages containing caffeine, and fruit juices are not appropriate. If the child is breastfed, breastfeeding should continue.

As the symptoms subside, the person may gradually add foods to the diet. Although often recommended, 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.

A doctor may give adults antinausea medications, such as ondansetron, prochlorperazine, and promethazine, by mouth or as an injection or suppository. Children who are still vomiting after 24 hours need to be seen again by a doctor.

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 medication to control the diarrhea, such as diphenoxylate, or instruct the person to use an over-the-counter medication, such as loperamide. These medications (called antidiarrheal medications) are not given to children under 18 years of age with acute diarrhea. Antidiarrheal medications are also not given to people who have recently used antibiotics, who have bloody diarrhea, who have small amounts of blood in the stool that are too small to be seen, or who have diarrhea and fever.

Because antibiotics can cause diarrhea and may encourage the growth of organisms resistant to antibiotics, they are usually best avoided, 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 Clostridioides difficile. The antibiotic that is used for treatment is different from the antibiotic that caused the Clostridioides difficile infection. (See also table Microorganisms That Cause Gastroenteritis.)

Parasitic infections are treated with antiparasitic medications such as metronidazole, tinidazole, and nitazoxanide.

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, there is insufficient evidence that probiotics prevent more serious consequences of gastroenteritis, such as the need for intravenous fluids or for hospitalization, to support their routine use to treat or prevent infectious diarrhea.