Anaphylaxis

From Wikipedia, the free encyclopedia

https://en.wikipedia.org/wiki/Anaphylaxis 

 

Anaphylaxis
Other names	Anaphylactoid, anaphylactic shock
Angioedema of the face such that the boy cannot open his eyes. This reaction was caused by an allergen exposure.
Specialty	Allergy and immunology
Symptoms	Itchy rash, throat swelling, shortness of breath, lightheadedness
Usual onset	Over minutes to hours
Causes	Insect bites, foods, medications
Diagnostic method	Based on symptoms
Differential diagnosis	Allergic reaction, angioedema, asthma exacerbation, carcinoid syndrome
Treatment	Epinephrine, intravenous fluids
Frequency	0.05–2%

Anaphylaxis is a serious allergic reaction that is rapid in onset and may cause death. It typically causes more than one of the following: an itchy rash, throat or tongue swelling, shortness of breath, vomiting, lightheadedness, and low blood pressure. These symptoms typically come on over minutes to hours.

Common causes include insect bites and stings, foods, and medications. Other causes include latex exposure and exercise. Additionally, cases may occur without an obvious reason. The mechanism involves the release of mediators from certain types of white blood cells triggered by either immunologic or non-immunologic mechanisms. Diagnosis is based on the presenting symptoms and signs after exposure to a potential allergen.

The primary treatment of anaphylaxis is epinephrine injection into a muscle, intravenous fluids, and positioning the person flat. Additional doses of epinephrine may be required. Other measures, such as antihistamines and steroids, are complementary. Carrying an epinephrine autoinjector and identification regarding the condition is recommended in people with a history of anaphylaxis.

Worldwide, 0.05–2% of the population is estimated to experience anaphylaxis at some point in life. Rates appear to be increasing. It occurs most often in young people and females. Of people who go to a hospital with anaphylaxis in the United States about 99.7% survive. The term comes from the Ancient Greek: ἀνά, romanized: ana, lit. 'against', and the Ancient Greek: φύλαξις, romanized: phylaxis, lit. 'protection'.

Signs and symptoms

Signs and symptoms of anaphylaxis

Anaphylaxis typically presents many different symptoms over minutes or hours with an average onset of 5 to 30 minutes if exposure is intravenous and 2 hours if from eating food. The most common areas affected include: skin (80–90%), respiratory (70%), gastrointestinal (30–45%), heart and vasculature (10–45%), and central nervous system (10–15%) with usually two or more being involved.

Skin

Urticaria and flushing on the back of a person with anaphylaxis

Symptoms typically include generalized hives, itchiness, flushing, or swelling (angioedema) of the afflicted tissues. Those with angioedema may describe a burning sensation of the skin rather than itchiness. Swelling of the tongue or throat occurs in up to about 20% of cases. Other features may include a runny nose and swelling of the conjunctiva. The skin may also be blue tinged because of lack of oxygen.

Respiratory

Respiratory symptoms and signs that may be present include shortness of breath, wheezes, or stridor. The wheezing is typically caused by spasms of the bronchial muscles while stridor is related to upper airway obstruction secondary to swelling. Hoarseness, pain with swallowing, or a cough may also occur.

Cardiovascular

While a fast heart rate caused by low blood pressure is more common, a Bezold–Jarisch reflex has been described in 10% of people, where a slow heart rate is associated with low blood pressure. A drop in blood pressure or shock (either distributive or cardiogenic) may cause the feeling of lightheadedness or loss of consciousness. Rarely very low blood pressure may be the only sign of anaphylaxis.

Coronary artery spasm may occur with subsequent myocardial infarction, dysrhythmia, or cardiac arrest. Those with underlying coronary disease are at greater risk of cardiac effects from anaphylaxis. The coronary spasm is related to the presence of histamine-releasing cells in the heart.

Other

Gastrointestinal symptoms may include crampy abdominal pain, diarrhea, and vomiting. There may be confusion, a loss of bladder control or pelvic pain similar to that of uterine cramps. Dilation of blood vessels around the brain may cause headaches. A feeling of anxiety or of "impending doom" has also been described.

Causes

Anaphylaxis can occur in response to almost any foreign substance. Common triggers include venom from insect bites or stings, foods, and medication. Foods are the most common trigger in children and young adults while medications and insect bites and stings are more common in older adults. Less common causes include: physical factors, biological agents such as semen, latex, hormonal changes, food additives such as monosodium glutamate and food colors, and topical medications. Physical factors such as exercise (known as exercise-induced anaphylaxis) or temperature (either hot or cold) may also act as triggers through their direct effects on mast cells. Events caused by exercise are frequently associated with the ingestion of certain foods. During anesthesia, neuromuscular blocking agents, antibiotics, and latex are the most common causes. The cause remains unknown in 32–50% of cases, referred to as "idiopathic anaphylaxis." Six vaccines (MMR, varicella, influenza, hepatitis B, tetanus, meningococcal) are recognized as a cause for anaphylaxis, and HPV may cause anaphylaxis as well. Physical exercise is an uncommon cause of anaphylaxis; in about a third of such cases there is a co-factor like taking an NSAID or eating a specific food prior to exercising.

Food

Many foods can trigger anaphylaxis; this may occur upon the first known ingestion. Common triggering foods vary around the world. In Western cultures, ingestion of or exposure to peanuts, wheat, nuts, certain types of seafood like shellfish, milk, and eggs are the most prevalent causes. Sesame is common in the Middle East, while rice and chickpeas are frequently encountered as sources of anaphylaxis in Asia. Severe cases are usually caused by ingesting the allergen, but some people experience a severe reaction upon contact. Children can outgrow their allergies. By age 16, 80% of children with anaphylaxis to milk or eggs and 20% who experience isolated anaphylaxis to peanuts can tolerate these foods.

Medication

Any medication may potentially trigger anaphylaxis. The most common are β-lactam antibiotics (such as penicillin) followed by aspirin and NSAIDs. Other antibiotics are implicated less frequently. Anaphylactic reactions to NSAIDs are either agent specific or occur among those that are structurally similar meaning that those who are allergic to one NSAID can typically tolerate a different one or different group of NSAIDs. Other relatively common causes include chemotherapy, vaccines, protamine and herbal preparations. Some medications (vancomycin, morphine, x-ray contrast among others) cause anaphylaxis by directly triggering mast cell degranulation.

The frequency of a reaction to an agent partly depends on the frequency of its use and partly on its intrinsic properties. Anaphylaxis to penicillin or cephalosporins occurs only after it binds to proteins inside the body with some agents binding more easily than others. Anaphylaxis to penicillin occurs once in every 2,000 to 10,000 courses of treatment, with death occurring in fewer than one in every 50,000 courses of treatment. Anaphylaxis to aspirin and NSAIDs occurs in about one in every 50,000 persons. If someone has a reaction to penicillins, his or her risk of a reaction to cephalosporins is greater but still less than one in 1,000. The old radiocontrast agents caused reactions in 1% of cases, while the newer lower osmolar agents cause reactions in 0.04% of cases.

Venom

Venom from stinging or biting insects such as Hymenoptera (ants, bees, and wasps) or Triatominae (kissing bugs) may cause anaphylaxis in susceptible people. Previous reactions, that are anything more than a local reaction around the site of the sting, are a risk factor for future anaphylaxis; however, half of fatalities have had no previous systemic reaction.

Risk factors

People with atopic diseases such as asthma, eczema, or allergic rhinitis are at high risk of anaphylaxis from food, latex, and radiocontrast agents but not from injectable medications or stings. One study in children found that 60% had a history of previous atopic diseases, and of children who die from anaphylaxis, more than 90% have asthma. Those with mastocytosis or of a higher socioeconomic status are at increased risk. The longer the time since the last exposure to the agent in question, the lower the risk.

Pathophysiology

Anaphylaxis is a severe allergic reaction of rapid onset affecting many body systems. It is due to the release of inflammatory mediators and cytokines from mast cells and basophils, typically due to an immunologic reaction but sometimes non-immunologic mechanism.

Immunologic

In the immunologic mechanism, immunoglobulin E (IgE) binds to the antigen (the foreign material that provokes the allergic reaction). Antigen-bound IgE then activates FcεRI receptors on mast cells and basophils. This leads to the release of inflammatory mediators such as histamine. These mediators subsequently increase the contraction of bronchial smooth muscles, trigger vasodilation, increase the leakage of fluid from blood vessels, and cause heart muscle depression. There is also an immunologic mechanism that does not rely on IgE, but it is not known if this occurs in humans.

Non-immunologic

Non-immunologic mechanisms involve substances that directly cause the degranulation of mast cells and basophils. These include agents such as contrast medium, opioids, temperature (hot or cold), and vibration. Sulfites may cause reactions by both immunologic and non-immunologic mechanisms.

Diagnosis

Anaphylaxis is diagnosed on the basis of a person's signs and symptoms. When any one of the following three occurs within minutes or hours of exposure to an allergen there is a high likelihood of anaphylaxis:

1. Involvement of the skin or mucosal tissue plus either respiratory difficulty or a low blood pressure causing symptoms
2. Two or more of the following symptoms after a likely contact with an allergen:

   a. Involvement of the skin or mucosa

   b. Respiratory difficulties

   c. Low blood pressure

   d. Gastrointestinal symptoms

3. Low blood pressure after exposure to a known allergen

Skin involvement may include: hives, itchiness or a swollen tongue among others. Respiratory difficulties may include: shortness of breath, stridor, or low oxygen levels among others. Low blood pressure is defined as a greater than 30% decrease from a person's usual blood pressure. In adults a systolic blood pressure of less than 90 mmHg is often used.

During an attack, blood tests for tryptase or histamine (released from mast cells) might be useful in diagnosing anaphylaxis due to insect stings or medications. However these tests are of limited use if the cause is food or if the person has a normal blood pressure, and they are not specific for the diagnosis.

Classification

There are three main classifications of anaphylaxis. Anaphylactic shock is associated with systemic vasodilation that causes low blood pressure which is by definition 30% lower than the person's baseline or below standard values. Biphasic anaphylaxis is the recurrence of symptoms within 1–72 hours with no further exposure to the allergen. Reports of incidence vary, with some studies claiming as many as 20% of cases. The recurrence typically occurs within 8 hours. It is managed in the same manner as anaphylaxis. Pseudoanaphylaxis or anaphylactoid reactions are a type of anaphylaxis that does not involve an allergic reaction but is due to direct mast cell degranulation. Non-immune anaphylaxis is the current term used by the World Allergy Organization with some recommending that the old terminology no longer be used.

Allergy testing

Skin allergy testing being carried out on the right arm

 

Patch test

Allergy testing may help in determining the trigger. Skin allergy testing is available for certain foods and venoms. Blood testing for specific IgE can be useful to confirm milk, egg, peanut, tree nut and fish allergies.

Skin testing is available to confirm penicillin allergies, but is not available for other medications. Non-immune forms of anaphylaxis can only be determined by history or exposure to the allergen in question, and not by skin or blood testing.

Differential diagnosis

It can sometimes be difficult to distinguish anaphylaxis from asthma, syncope, and panic attacks. Asthma however typically does not entail itching or gastrointestinal symptoms, syncope presents with pallor rather than a rash, and a panic attack may have flushing but does not have hives. Other conditions that may present similarly include: scrombroidosis and anisakiasis.

Post-mortem findings

In a person who died from anaphylaxis, autopsy may show an "empty heart" attributed to reduced venous return from vasodilation and redistribution of intravascular volume from the central to the peripheral compartment. Other signs are laryngeal edema, eosinophilia in lungs, heart and tissues, and evidence of myocardial hypoperfusion. Laboratory findings could detect increased levels of serum tryptase, increase in total and specific IgE serum levels.

Prevention

Avoidance of the trigger of anaphylaxis is recommended. In cases where this may not be possible, desensitization may be an option. Immunotherapy with Hymenoptera venoms is effective at desensitizing 80–90% of adults and 98% of children against allergies to bees, wasps, hornets, yellowjackets, and fire ants. Oral immunotherapy may be effective at desensitizing some people to certain food including milk, eggs, nuts and peanuts; however, adverse effects are common. For example, many people develop an itchy throat, cough, or lip swelling during immunotherapy. Desensitization is also possible for many medications, however it is advised that most people simply avoid the agent in question. In those who react to latex it may be important to avoid cross-reactive foods such as avocados, bananas, and potatoes among others.

Management

Anaphylaxis is a medical emergency that may require resuscitation measures such as airway management, supplemental oxygen, large volumes of intravenous fluids, and close monitoring. Passive leg raise may also be helpful in the emergency management.

Administration of epinephrine is the treatment of choice with antihistamines and steroids (for example, dexamethasone) often used as adjuncts. A period of in-hospital observation for between 2 and 24 hours is recommended for people once they have returned to normal due to concerns of biphasic anaphylaxis.

Epinephrine

An old version of an EpiPen auto-injector

Epinephrine (adrenaline) is the primary treatment for anaphylaxis with no absolute contraindication to its use. It is recommended that an epinephrine solution be given intramuscularly into the mid anterolateral thigh as soon as the diagnosis is suspected. The injection may be repeated every 5 to 15 minutes if there is insufficient response. A second dose is needed in 16–35% of episodes with more than two doses rarely required. The intramuscular route is preferred over subcutaneous administration because the latter may have delayed absorption. Minor adverse effects from epinephrine include tremors, anxiety, headaches, and palpitations.

People on β-blockers may be resistant to the effects of epinephrine. In this situation if epinephrine is not effective intravenous glucagon can be administered which has a mechanism of action independent of β-receptors.

If necessary, it can also be given intravenously using a dilute epinephrine solution. Intravenous epinephrine, however, has been associated both with dysrhythmia and myocardial infarction. Epinephrine autoinjectors used for self-administration typically come in two doses, one for adults or children who weigh more than 25 kg and one for children who weigh 10 to 25 kg.

Adjuncts

Antihistamines (both H1 and H2), while commonly used and assumed effective based on theoretical reasoning, are poorly supported by evidence. A 2007 Cochrane review did not find any good-quality studies upon which to base recommendations and they are not believed to have an effect on airway edema or spasm. Corticosteroids are unlikely to make a difference in the current episode of anaphylaxis, but may be used in the hope of decreasing the risk of biphasic anaphylaxis. Their prophylactic effectiveness in these situations is uncertain. Nebulized salbutamol may be effective for bronchospasm that does not resolve with epinephrine. Methylene blue has been used in those not responsive to other measures due to its presumed effect of relaxing smooth muscle.

Preparedness

People prone to anaphylaxis are advised to have an "allergy action plan." Parents are advised to inform schools of their children's allergies and what to do in case of an anaphylactic emergency. The action plan usually includes use of epinephrine autoinjectors, the recommendation to wear a medical alert bracelet, and counseling on avoidance of triggers. Immunotherapy is available for certain triggers to prevent future episodes of anaphylaxis. A multi-year course of subcutaneous desensitization has been found effective against stinging insects, while oral desensitization is effective for many foods.

Prognosis

In those in whom the cause is known and prompt treatment is available, the prognosis is good. Even if the cause is unknown, if appropriate preventative medication is available, the prognosis is generally good. If death occurs, it is usually due to either respiratory (typically asphyxia) or cardiovascular causes (shock), with 0.7–20% of cases causing death. There have been cases of death occurring within minutes. Outcomes in those with exercise-induced anaphylaxis are typically good, with fewer and less severe episodes as people get older.

Epidemiology

The number of people who get anaphylaxis is 4–100 per 100,000 persons per year, with a lifetime risk of 0.05–2%. About 30% of people get more than one attack. Exercise-induced anaphylaxis affects about 1 in 2000 young people.

Rates appear to be increasing: with the numbers in the 1980s being approximately 20 per 100,000 per year, while in the 1990s it was 50 per 100,000 per year. The increase appears to be primarily for food-induced anaphylaxis. The risk is greatest in young people and females.

Anaphylaxis leads to as many as 500–1,000 deaths per year (2.7 per million) in the United States, 20 deaths per year in the United Kingdom (0.33 per million), and 15 deaths per year in Australia (0.64 per million). Another estimate from the United States puts the death rate at 0.7 per million. Mortality rates have decreased between the 1970s and 2000s. In Australia, death from food-induced anaphylaxis occur primarily in women while deaths due to insect bites primarily occur in males. Death from anaphylaxis is most commonly triggered by medications.

History

The term aphylaxis was coined by Charles Richet in 1902 and later changed to anaphylaxis due to its nicer quality of speech. In his experiments, Richet injected a dog with sea anemone (Actinia) toxin in an attempt to protect it. Although the dog had previously tolerated the toxin, on re-exposure, three weeks later with the same dose, it developed fatal anaphylaxis. Thus instead of inducing tolerance (prophylaxis), when lethal responses resulted from previously tolerated doses, he coined the word a (without) phylaxis (protection). He was subsequently awarded the Nobel Prize in Physiology or Medicine for his work on anaphylaxis in 1913. The phenomenon itself, however, has been described since ancient times. The term comes from the Greek words ἀνά, ana, meaning "against", and φύλαξις, phylaxis, meaning "protection".

Research

There are ongoing efforts to develop sublingual epinephrine to treat anaphylaxis. Subcutaneous injection of the anti-IgE antibody omalizumab is being studied as a method of preventing recurrence, but it is not yet recommended.

Gastroenteritis

From Wikipedia, the free encyclopedia

https://en.wikipedia.org/wiki/Gastroenteritis 

 

Gastroenteritis
Other names	Gastro, stomach bug, stomach virus, stomach flu, gastric flu, gastrointestinitis
Gastroenteritis viruses: A = rotavirus, B = adenovirus, C = norovirus and D = astrovirus. The virus particles are shown at the same magnification to allow size comparison.
Specialty	Infectious disease
Symptoms	Diarrhea, vomiting, abdominal pain, fever
Complications	Dehydration
Causes	Viruses, bacteria, parasites, fungus
Diagnostic method	Based on symptoms, occasionally stool culture
Differential diagnosis	Inflammatory bowel disease, malabsorption syndrome, lactose intolerance
Prevention	Hand washing, drinking clean water, proper disposal of human waste, breastfeeding
Treatment	Oral rehydration solution (combination of water, salts, and sugar), intravenous fluids
Frequency	2.4 billion (2015)
Deaths	1.3 million (2015)

Gastroenteritis, also known as infectious diarrhea, is inflammation of the gastrointestinal tract—the stomach and small intestine. Symptoms may include diarrhea, vomiting and abdominal pain. Fever, lack of energy and dehydration may also occur. This typically lasts less than two weeks. It is not related to influenza, though it has erroneously been called the "stomach flu".

Gastroenteritis is usually caused by viruses. However, bacteria, parasites, and fungus can also cause gastroenteritis. In children, rotavirus is the most common cause of severe disease. In adults, norovirus and Campylobacter are common causes. Eating improperly prepared food, drinking contaminated water or close contact with a person who is infected can spread the disease. Treatment is generally the same with or without a definitive diagnosis, so testing to confirm is usually not needed.

Prevention includes hand washing with soap, drinking clean water, proper disposal of human waste and breastfeeding babies instead of using formula. The rotavirus vaccine is recommended as a prevention for children. Treatment involves getting enough fluids. For mild or moderate cases, this can typically be achieved by drinking oral rehydration solution (a combination of water, salts and sugar). In those who are breastfed, continued breastfeeding is recommended. For more severe cases, intravenous fluids may be needed. Fluids may also be given by a nasogastric tube. Zinc supplementation is recommended in children. Antibiotics are generally not needed. However, antibiotics are recommended for young children with a fever and bloody diarrhea.

In 2015, there were two billion cases of gastroenteritis, resulting in 1.3 million deaths globally. Children and those in the developing world are affected the most. In 2011, there were about 1.7 billion cases, resulting in about 700,000 deaths of children under the age of five. In the developing world, children less than two years of age frequently get six or more infections a year. It is less common in adults, partly due to the development of immunity.

Signs and symptoms

Bristol stool chart

Gastroenteritis usually involves both diarrhea and vomiting. Sometimes, only one or the other is present. This may be accompanied by abdominal cramps. Signs and symptoms usually begin 12–72 hours after contracting the infectious agent. If due to a virus, the condition usually resolves within one week. Some viral infections also involve fever, fatigue, headache and muscle pain. If the stool is bloody, the cause is less likely to be viral and more likely to be bacterial. Some bacterial infections cause severe abdominal pain and may persist for several weeks.

Children infected with rotavirus usually make a full recovery within three to eight days. However, in poor countries treatment for severe infections is often out of reach and persistent diarrhea is common. Dehydration is a common complication of diarrhea. Severe dehydration in children may be recognized if the skin color and position returns slowly when pressed. This is called "prolonged capillary refill" and "poor skin turgor". Abnormal breathing is another sign of severe dehydration. Repeat infections are typically seen in areas with poor sanitation, and malnutrition. Stunted growth and long-term cognitive delays can result.

Reactive arthritis occurs in 1% of people following infections with Campylobacter species. Guillain–Barré syndrome occurs in 0.1%. Hemolytic uremic syndrome (HUS) may occur due to infection with Shiga toxin-producing Escherichia coli or Shigella species. HUS causes low platelet counts, poor kidney function, and low red blood cell count (due to their breakdown). Children are more predisposed to getting HUS than adults. Some viral infections may produce benign infantile seizures.

Cause

Viruses (particularly rotavirus) and the bacteria Escherichia coli and Campylobacter species are the primary causes of gastroenteritis. There are, however, many other infectious agents that can cause this syndrome including parasites and fungus. Non-infectious causes are seen on occasion, but they are less likely than a viral or bacterial cause. Risk of infection is higher in children due to their lack of immunity. Children are also at higher risk because they are less likely to practice good hygiene habits. Children living in areas without easy access to water and soap are especially vulnerable.

Viral

Rotavirus, norovirus, adenovirus, and astrovirus are known to cause viral gastroenteritis. Rotavirus is the most common cause of gastroenteritis in children, and produces similar rates in both the developed and developing world. Viruses cause about 70% of episodes of infectious diarrhea in the pediatric age group. Rotavirus is a less common cause in adults due to acquired immunity. Norovirus is the cause in about 18% of all cases.

Norovirus is the leading cause of gastroenteritis among adults in America, causing greater than 90% of outbreaks. These localized epidemics typically occur when groups of people spend time in close physical proximity to each other, such as on cruise ships, in hospitals, or in restaurants. People may remain infectious even after their diarrhea has ended. Norovirus is the cause of about 10% of cases in children.

Bacterial

Salmonella enterica serovar Typhimurium (ATCC 14028) as seen with a microscope at 1000 fold magnification and following Gram staining.

In the developed world Campylobacter jejuni is the primary cause of bacterial gastroenteritis, with half of these cases associated with exposure to poultry. In children, bacteria are the cause in about 15% of cases, with the most common types being Escherichia coli, Salmonella, Shigella, and Campylobacter species. If food becomes contaminated with bacteria and remains at room temperature for a period of several hours, the bacteria multiply and increase the risk of infection in those who consume the food. Some foods commonly associated with illness include raw or undercooked meat, poultry, seafood, and eggs; raw sprouts; unpasteurized milk and soft cheeses; and fruit and vegetable juices. In the developing world, especially sub-Saharan Africa and Asia, cholera is a common cause of gastroenteritis. This infection is usually transmitted by contaminated water or food.

Toxigenic Clostridium difficile is an important cause of diarrhea that occurs more often in the elderly. Infants can carry these bacteria without developing symptoms. It is a common cause of diarrhea in those who are hospitalized and is frequently associated with antibiotic use. Staphylococcus aureus infectious diarrhea may also occur in those who have used antibiotics. Acute "traveler's diarrhea" is usually a type of bacterial gastroenteritis, while the persistent form is usually parasitic. Acid-suppressing medication appears to increase the risk of significant infection after exposure to a number of organisms, including Clostridium difficile, Salmonella, and Campylobacter species. The risk is greater in those taking proton pump inhibitors than with H2 antagonists.

Parasitic

A number of parasites can cause gastroenteritis. Giardia lamblia is most common, but Entamoeba histolytica, Cryptosporidium spp., and other species have also been implicated. As a group, these agents comprise about 10% of cases in children. Giardia occurs more commonly in the developing world, but this type of illness can occur nearly everywhere. It occurs more commonly in persons who have traveled to areas with high prevalence, children who attend day care, men who have sex with men, and following disasters.

Transmission

Transmission may occur from drinking contaminated water or when people share personal objects. Water quality typically worsens during the rainy season and outbreaks are more common at this time. In areas with four seasons, infections are more common in the winter. Worldwide, bottle-feeding of babies with improperly sanitized bottles is a significant cause. Transmission rates are also related to poor hygiene, (especially among children), in crowded households, and in those with poor nutritional status. Adults who have developed immunities might still carry certain organisms without exhibiting symptoms. Thus, adults can become natural reservoirs of certain diseases. While some agents (such as Shigella) only occur in primates, others (such as Giardia) may occur in a wide variety of animals.

Non-infectious

There are a number of non-infectious causes of inflammation of the gastrointestinal tract. Some of the more common include medications (like NSAIDs), certain foods such as lactose (in those who are intolerant), and gluten (in those with celiac disease). Crohn's disease is also a non-infectious source of (often severe) gastroenteritis. Disease secondary to toxins may also occur. Some food-related conditions associated with nausea, vomiting, and diarrhea include: ciguatera poisoning due to consumption of contaminated predatory fish, scombroid associated with the consumption of certain types of spoiled fish, tetrodotoxin poisoning from the consumption of puffer fish among others, and botulism typically due to improperly preserved food.

In the United States, rates of emergency department use for noninfectious gastroenteritis dropped 30% from 2006 until 2011. Of the twenty most common conditions seen in the emergency department, rates of noninfectious gastroenteritis had the largest decrease in visits in that time period.

Pathophysiology

Gastroenteritis caused due to intestinal infection.

Gastroenteritis is defined as vomiting or diarrhea due to inflammation of the small or large bowel, often due to infection. The changes in the small bowel are typically noninflammatory, while the ones in the large bowel are inflammatory. The number of pathogens required to cause an infection varies from as few as one (for Cryptosporidium) to as many as 10⁸ (for Vibrio cholerae).

Diagnosis

Gastroenteritis is typically diagnosed clinically, based on a person's signs and symptoms. Determining the exact cause is usually not needed as it does not alter management of the condition.

However, stool cultures should be performed in those with blood in the stool, those who might have been exposed to food poisoning, and those who have recently traveled to the developing world. It may also be appropriate in children younger than 5, old people, and those with poor immune function. Diagnostic testing may also be done for surveillance. As hypoglycemia occurs in approximately 10% of infants and young children, measuring serum glucose in this population is recommended. Electrolytes and kidney function should also be checked when there is a concern about severe dehydration.

Dehydration

A determination of whether or not the person has dehydration is an important part of the assessment, with dehydration typically divided into mild (3–5%), moderate (6–9%), and severe (≥10%) cases. In children, the most accurate signs of moderate or severe dehydration are a prolonged capillary refill, poor skin turgor, and abnormal breathing. Other useful findings (when used in combination) include sunken eyes, decreased activity, a lack of tears, and a dry mouth. A normal urinary output and oral fluid intake is reassuring. Laboratory testing is of little clinical benefit in determining the degree of dehydration. Thus the use of urine testing or ultrasounds is generally not needed.

Differential diagnosis

Other potential causes of signs and symptoms that mimic those seen in gastroenteritis that need to be ruled out include appendicitis, volvulus, inflammatory bowel disease, urinary tract infections, and diabetes mellitus. Pancreatic insufficiency, short bowel syndrome, Whipple's disease, coeliac disease, and laxative abuse should also be considered. The differential diagnosis can be complicated somewhat if the person exhibits only vomiting or diarrhea (rather than both).

Appendicitis may present with vomiting, abdominal pain, and a small amount of diarrhea in up to 33% of cases. This is in contrast to the large amount of diarrhea that is typical of gastroenteritis. Infections of the lungs or urinary tract in children may also cause vomiting or diarrhea. Classical diabetic ketoacidosis (DKA) presents with abdominal pain, nausea, and vomiting, but without diarrhea. One study found that 17% of children with DKA were initially diagnosed as having gastroenteritis.

Prevention

Percentage of rotavirus tests with positive results, by surveillance week, United States, July 2000 – June 2009.

Lifestyle

A supply of easily accessible uncontaminated water and good sanitation practices are important for reducing rates of infection and clinically significant gastroenteritis. Personal measures (such as hand washing with soap) have been found to decrease rates of gastroenteritis in both the developing and developed world by as much as 30%. Alcohol-based gels may also be effective. Food or drink that is thought to be contaminated should be avoided. Breastfeeding is important, especially in places with poor hygiene, as is improvement of hygiene generally. Breast milk reduces both the frequency of infections and their duration.

Vaccination

Due to both its effectiveness and safety, in 2009 the World Health Organization recommended that the rotavirus vaccine be offered to all children globally. Two commercial rotavirus vaccines exist and several more are in development. In Africa and Asia these vaccines reduced severe disease among infants and countries that have put in place national immunization programs have seen a decline in the rates and severity of disease. This vaccine may also prevent illness in non-vaccinated children by reducing the number of circulating infections. Since 2000, the implementation of a rotavirus vaccination program in the United States has substantially decreased the number of cases of diarrhea by as much as 80 percent. The first dose of vaccine should be given to infants between 6 and 15 weeks of age. The oral cholera vaccine has been found to be 50–60% effective over 2 years.

Management

Gastroenteritis is usually an acute and self-limiting disease that does not require medication. The preferred treatment in those with mild to moderate dehydration is oral rehydration therapy (ORT). For children at risk of dehydration from vomiting, taking a single dose of the anti vomiting medication metoclopramide or ondansetron, may be helpful, and butylscopolamine is useful in treating abdominal pain.

Rehydration

The primary treatment of gastroenteritis in both children and adults is rehydration. This is preferably achieved by drinking rehydration solution, although intravenous delivery may be required if there is a decreased level of consciousness or if dehydration is severe. Drinking replacement therapy products made with complex carbohydrates (i.e. those made from wheat or rice) may be superior to those based on simple sugars. Drinks especially high in simple sugars, such as soft drinks and fruit juices, are not recommended in children under 5 years of age as they may increase diarrhea. Plain water may be used if more specific ORT preparations are unavailable or the person is not willing to drink them. A nasogastric tube can be used in young children to administer fluids if warranted. In those who require intravenous fluids, one to four hours' worth is often sufficient.

Dietary

It is recommended that breast-fed infants continue to be nursed in the usual fashion, and that formula-fed infants continue their formula immediately after rehydration with ORT. Lactose-free or lactose-reduced formulas usually are not necessary. Children should continue their usual diet during episodes of diarrhea with the exception that foods high in simple sugars should be avoided. The BRAT diet (bananas, rice, applesauce, toast and tea) is no longer recommended, as it contains insufficient nutrients and has no benefit over normal feeding.

Some probiotics have been shown to be beneficial in reducing both the duration of illness and the frequency of stools. They may also be useful in preventing and treating antibiotic associated diarrhea. Fermented milk products (such as yogurt) are similarly beneficial. Zinc supplementation appears to be effective in both treating and preventing diarrhea among children in the developing world.

Antiemetics

Antiemetic medications may be helpful for treating vomiting in children. Ondansetron has some utility, with a single dose being associated with less need for intravenous fluids, fewer hospitalizations, and decreased vomiting. Metoclopramide might also be helpful. However, the use of ondansetron might possibly be linked to an increased rate of return to hospital in children. The intravenous preparation of ondansetron may be given orally if clinical judgment warrants. Dimenhydrinate, while reducing vomiting, does not appear to have a significant clinical benefit.

Antibiotics

Antibiotics are not usually used for gastroenteritis, although they are sometimes recommended if symptoms are particularly severe or if a susceptible bacterial cause is isolated or suspected. If antibiotics are to be employed, a macrolide (such as azithromycin) is preferred over a fluoroquinolone due to higher rates of resistance to the latter. Pseudomembranous colitis, usually caused by antibiotic use, is managed by discontinuing the causative agent and treating it with either metronidazole or vancomycin. Bacteria and protozoans that are amenable to treatment include Shigella Salmonella typhi, and Giardia species. In those with Giardia species or Entamoeba histolytica, tinidazole treatment is recommended and superior to metronidazole. The World Health Organization (WHO) recommends the use of antibiotics in young children who have both bloody diarrhea and fever.

Antimotility agents

Antimotility medication has a theoretical risk of causing complications, and although clinical experience has shown this to be unlikely, these drugs are discouraged in people with bloody diarrhea or diarrhea that is complicated by fever. Loperamide, an opioid analogue, is commonly used for the symptomatic treatment of diarrhea. Loperamide is not recommended in children, however, as it may cross the immature blood–brain barrier and cause toxicity. Bismuth subsalicylate, an insoluble complex of trivalent bismuth and salicylate, can be used in mild to moderate cases, but salicylate toxicity is theoretically possible.

Epidemiology

Deaths due to diarrhoeal diseases per million persons in 2012

  0–2

  3–10

  11–18

  19–30

  31–46

  47–80

  81–221

  222–450

  451–606

  607–1799

Disability-adjusted life year for diarrhea per 100,000 inhabitants in 2004.

no data   ≤less 500   500–1000   1000–1500   1500–2000   2000–2500   2500–3000

3000–3500   3500–4000   4000–4500   4500–5000   5000–6000   ≥6000

It is estimated that there were two billion cases of gastroenteritis that resulted in 1.3 million deaths globally in 2015. Children and those in the developing world are most commonly affected.^[15] As of 2011, in those less than five, there were about 1.7 billion cases resulting in 0.7 million deaths,^[16] with most of these occurring in the world's poorest nations. More than 450,000 of these fatalities are due to rotavirus in children under 5 years of age. Cholera causes about three to five million cases of disease and kills approximately 100,000 people yearly. In the developing world, children less than two years of age frequently get six or more infections a year that result in significant gastroenteritis. It is less common in adults, partly due to the development of acquired immunity.

In 1980, gastroenteritis from all causes caused 4.6 million deaths in children, with the majority occurring in the developing world. Death rates were reduced significantly (to approximately 1.5 million deaths annually) by the year 2000, largely due to the introduction and widespread use of oral rehydration therapy. In the US, infections causing gastroenteritis are the second most common infection (after the common cold), and they result in between 200 and 375 million cases of acute diarrhea and approximately ten thousand deaths annually, with 150 to 300 of these deaths in children less than five years of age.

History

The first usage of "gastroenteritis" was in 1825. Before this time it was commonly known as typhoid fever or "cholera morbus", among others, or less specifically as "griping of the guts", "surfeit", "flux", "colic", "bowel complaint", or any one of a number of other archaic names for acute diarrhea. Cholera morbus is a historical term that was used to refer to gastroenteritis rather than specifically cholera.

Society and culture

Gastroenteritis is associated with many colloquial names, including "Montezuma's revenge", "Delhi belly", "la turista", and "back door sprint", among others. It has played a role in many military campaigns and is believed to be the origin of the term "no guts no glory".

Gastroenteritis is the main reason for 3.7 million visits to physicians a year in the United States and 3 million visits in France. In the United States gastroenteritis as a whole is believed to result in costs of US$23 billion per year with that due to rotavirus alone resulting in estimated costs of US$1 billion a year.

Research

There are a number of vaccines against gastroenteritis in development. For example, vaccines against Shigella and enterotoxigenic Escherichia coli (ETEC) are two of the leading bacterial causes of gastroenteritis worldwide.

Other animals

Many of the same agents cause gastroenteritis in cats and dogs as in humans. The most common organisms are Campylobacter, Clostridium difficile, Clostridium perfringens, and Salmonella. A large number of toxic plants may also cause symptoms.

Some agents are more specific to a certain species. Transmissible gastroenteritis coronavirus (TGEV) occurs in pigs resulting in vomiting, diarrhea, and dehydration. It is believed to be introduced to pigs by wild birds and there is no specific treatment available. It is not transmissible to humans.