What is acute gastroenteritis?


Gastroenteritis is characterized by loss of appetite, nausea, vomiting, moderate or severe diarrhea, and discomfort in the abdomen and is usually due to an infection acquired by eating contaminated food.

Gastroenteritis is a group of disorders caused by inflammation of the gastric mucosa and intestinal mucosa, whose primary symptom is diarrhea. It can be accompanied by other symptoms such as nausea and vomiting, loss of appetite, cramps, and discomfort in the abdomen. In more than 90% of cases, it is due to an infectious cause.

The transmission of infectious gastroenteritis usually occurs through the mouth by interacting with germs either from the hands or from the foods they carry.

Acute gastroenteritis is also commonly known as acute diarrhea. Diarrhea is considered acute when it does not exceed two weeks in duration. It is persistent when it lasts between two and four weeks and chronic if it lasts more than four weeks. This classification is essential because of the cause of diarrhea, the tests are done to study it, the treatment, and the prognosis vary greatly depending on the disease’s duration.

Acute gastroenteritis is a very common process, with an incidence in the Western world of between 0.5 and 2 episodes per person per year. It is widespread in summer if it is salmonella gastroenteritis or in winter in school outbreaks due to rotavirus. It is usually a benign disease that limits itself to a few days. However, it can lead to severe complications when it affects children, the elderly, or immunosuppressed patients. In developing countries, acute gastroenteritis is much more common, especially among children, and has a high mortality rate.

Likewise, and with the rise of global tourism, a type of gastroenteritis related to travel to other countries or continents known as traveler’s diarrhea is described.

Causes of acute gastroenteritis

Acute diarrhea can be caused by several reasons, although more than 90% have an infectious cause. Generally, gastroenteritis is caused by microorganisms found in water or food, usually contaminated by infected feces. The infection can also be transmitted from one person to another or by an animal, usually orally (putting hands to mouth after coming into contact with a possible focus of the syndrome).

Some bacteria can release certain substances, enterotoxin, that alter the intestinal mucosa, causing a release of sodium and chlorine with the subsequent expulsion of water. This mainly watery diarrhea is produced by bacteria such as Escherichia coli (traveler’sdiarrhea), Vibrio cholerae (cholera), or Shigella spp.

Other bacteria invade the intestinal mucous lining, causing organic damage to the intestinal wall and producing, in addition to water loss, liquid with high protein content. Sometimes this fluid contains mucus and blood; this gastroenteritis is known as dysenteriformdiarrhea. Some of the microorganisms that cause this type of gastroenteritis are Salmonella or Campylobacter.

Some bacteria, such as Clostridium difficile, cause diarrhea after courses of antibiotics that eliminate the usual intestinal flora and allow Clostridium to produce a harmful effect on the intestinal mucosa. They are especially serious in the elderly, and their transmission by contact from the first case can cause epidemic outbreaks in hospitals and residences.

Viruses can cause secretory diarrhea. In fact, in temperate climates, during winter, viruses are the main responsible for the proliferation of diarrhea, serious enough that children under four years of age have to be hospitalized. Some of the viruses that cause gastroenteritis are rotaviruses, enteric adenoviruses, or astroviruses.

Parasites can invade or adhere to the intestine causing nausea, vomiting, diarrhea, and general malaise. These parasites are Giardia lamblia and Cryptosporidium, which are usually acquired by drinking contaminated water.

Acute diarrhea that is not caused by infectious causes is usually due to the ingestion of toxic substances, lactose intolerance, ingestion of heavy metals, or certain drugs’ side effects.

Risk groups for acute gastroenteritis

Due to their greater exposure to the causative agents of gastroenteritis, the following groups are distinguished that can be more easily affected:

  • Travelers: almost 40% of tourists who come to endemic regions of Latin America, Africa, and Asia suffer from so-called traveler’s diarrhea. This is due to infections caused by bacteria to which the local population is accustomed.
  • People who habitually consume certain foods, such as mayonnaise, cream, eggs, or shellfish.
  • People with immunodeficiencies. People with low defenses may suffer diarrhea more frequently because their weakened immune system has difficulties fighting microorganisms (people with congenital immunodeficiencies, AIDS, under treatment with immunosuppressants, or older women).
  • Daycare staff and their families.
  • Those who reside in reception centers or hospitals.

The symptoms of gastroenteritis vary according to the origin of acute diarrhea and depend on the characteristics of the person who suffers from it. The symptoms of gastroenteritis usually start suddenly with loss of appetite, nausea, or vomiting. Also, bowel sounds, cramps, and diarrhea may appear, with or without the presence of mucus and blood. The intestine can expand due to gas and cause pain.

The patient may also have a fever and experience tiredness and muscle aches. The typical picture of fever and bloody diarrhea is known as dysentery.

Gastroenteritis can also present pain when defecating in the anal region and a sensation of incomplete evacuation due to inflammation of the rectum’s mucosa (rectal tenesmus). The stool characteristics are different according to some types of diarrhea, being very watery and greenish and pasty in those related to microorganisms such as Clostridium.

The symptoms of acute gastroenteritis can lead to marked dehydration and hypotension (lowering of blood pressure). Vomiting and diarrhea can cause a severe loss of potassium and sodium. These electrolyte imbalances are potentially severe.

There may also be muscle cramps if there is a significant loss of electrolytes or muscle and joint pain in those caused by viruses. Dehydration in children and the elderly can manifest as drowsiness or irritability.