Diarrhea (American English), also spelled diarrhoea or diarrhœa (British English), is the condition of having at least three loose, liquid, or watery bowel movements in a day.[2] It often lasts for a few days and can result in dehydration due to fluid loss.[2] Signs of dehydration often begin with loss of the normal stretchiness of the skin and irritable behaviour.[2] This can progress to decreased urination, loss of skin color, a fast heart rate, and a decrease in responsiveness as it becomes more severe.[2] Loose but non-watery stools in babies who are exclusively breastfed, however, are normal.[2]
The most common cause is an infection of the intestines due to a virus, bacterium, or parasite—a condition also known as gastroenteritis.[2] These infections are often acquired from food or water that has been contaminated by feces, or directly from another person who is infected.[2] The three types of diarrhea are: short duration watery diarrhea, short duration bloody diarrhea, and persistent diarrhea (lasting more than two weeks, which can be either watery or bloody).[2] The short duration watery diarrhea may be due to cholera, although this is rare in the developed world.[2] If blood is present, it is also known as dysentery.[2] A number of non-infectious causes can result in diarrhea.[5] These include lactose intolerance, irritable bowel syndrome, non-celiac gluten sensitivity, celiac disease, inflammatory bowel disease such as ulcerative colitis, hyperthyroidism, bile acid diarrhea, and a number of medications.[5][6][7] In most cases, stool cultures to confirm the exact cause are not required.[8]
Diarrhea can be prevented by improved sanitation, clean drinking water, and hand washing with soap.[2] Breastfeeding for at least six months and vaccination against rotavirus is also recommended.[2] Oral rehydration solution (ORS)—clean water with modest amounts of salts and sugar—is the treatment of choice.[2] Zinc tablets are also recommended.[2] These treatments have been estimated to have saved 50 million children in the past 25 years.[1] When people have diarrhea it is recommended that they continue to eat healthy food, and babies continue to be breastfed.[2] If commercial ORS is not available, homemade solutions may be used.[9] In those with severe dehydration, intravenous fluids may be required.[2] Most cases, however, can be managed well with fluids by mouth.[10] Antibiotics, while rarely used, may be recommended in a few cases such as those who have bloody diarrhea and a high fever, those with severe diarrhea following travelling, and those who grow specific bacteria or parasites in their stool.[8] Loperamide may help decrease the number of bowel movements but is not recommended in those with severe disease.[8]
About 1.7 to 5 billion cases of diarrhea occur per year.[2][5][11] It is most common in developing countries, where young children get diarrhea on average three times a year.[2] Total deaths from diarrhea are estimated at 1.53 million in 2019—down from 2.9 million in 1990.[4] In 2012, it was the second most common cause of deaths in children younger than five (0.76 million or 11%).[2][12] Frequent episodes of diarrhea are also a common cause of malnutrition and the most common cause in those younger than five years of age.[2] Other long term problems that can result include stunted growth and poor intellectual development.[12]
The word diarrhea is from the Ancient Greek διάρροια from διά dia "through" and ῥέω rheo "flow".
Diarrhea is the spelling in American English, whereas diarrhoea is the spelling in British English.
Slang terms for the condition include "the runs", "the squirts" (or "squits" in Britain[13]) and "the trots".[14][15]
The word is often pronounced as /ˌdaɪəˈriːə/ DY-ə-REE-ə.
Diarrhea is defined by the World Health Organization as having three or more loose or liquid stools per day, or as having more stools than is normal for that person.[2]
Acute diarrhea is defined as an abnormally frequent discharge of semisolid or fluid fecal matter from the bowel, lasting less than 14 days, by World Gastroenterology Organization.[16] Acute diarrhea that is watery may be known as AWD (Acute Watery Diarrhoea.)[17]
Secretory diarrhea means that there is an increase in the active secretion, or there is an inhibition of absorption. There is little to no structural damage. The most common cause of this type of diarrhea is a cholera toxin that stimulates the secretion of anions, especially chloride ions (Cl–). Therefore, to maintain a charge balance in the gastrointestinal tract, sodium (Na+) is carried with it, along with water. In this type of diarrhea intestinal fluid secretion is isotonic with plasma even during fasting.[18][19] It continues even when there is no oral food intake.
Osmotic diarrhea occurs when too much water is drawn into the bowels. If a person drinks solutions with excessive sugar or excessive salt, these can draw water from the body into the bowel and cause osmotic diarrhea.[20][19] Osmotic diarrhea can also result from maldigestion, e.g. pancreatic disease or coeliac disease, in which the nutrients are left in the lumen to pull in water. Or it can be caused by osmotic laxatives (which work to alleviate constipation by drawing water into the bowels). In healthy individuals, too much magnesium or vitamin C or undigested lactose can produce osmotic diarrhea and distention of the bowel. A person who has lactose intolerance can have difficulty absorbing lactose after an extraordinarily high intake of dairy products. In persons who have fructose malabsorption, excess fructose intake can also cause diarrhea. High-fructose foods that also have a high glucose content are more absorbable and less likely to cause diarrhea. Sugar alcohols such as sorbitol (often found in sugar-free foods) are difficult for the body to absorb and, in large amounts, may lead to osmotic diarrhea.[18] In most of these cases, osmotic diarrhea stops when the offending agent, e.g. milk or sorbitol, is stopped.
Exudative diarrhea occurs with the presence of blood and pus in the stool. This occurs with inflammatory bowel diseases, such as Crohn's disease or ulcerative colitis, and other severe infections such as E. coli or other forms of food poisoning.[19][18]
Inflammatory diarrhea occurs when there is damage to the mucosal lining or brush border, which leads to a passive loss of protein-rich fluids and a decreased ability to absorb these lost fluids. Features of all three of the other types of diarrhea can be found in this type of diarrhea.[21] It can be caused by bacterial infections, viral infections, parasitic infections, or autoimmune problems such as inflammatory bowel diseases. It can also be caused by tuberculosis, colon cancer, and enteritis.[19]
If there is blood visible in the stools, it is also known as dysentery. The blood is a trace of an invasion of bowel tissue. Dysentery is a symptom of, among others, Shigella, Entamoeba histolytica, and Salmonella.[19]
Diarrheal disease may have a negative impact on both physical fitness and mental development. "Early childhood malnutrition resulting from any cause reduces physical fitness and work productivity in adults",[22] and diarrhea is a primary cause of childhood malnutrition.[23] Further, evidence suggests that diarrheal disease has significant impacts on mental development and health; it has been shown that, even when controlling for helminth infection and early breastfeeding, children who had experienced severe diarrhea had significantly lower scores on a series of tests of intelligence.[22][24]
Diarrhea can cause electrolyte imbalances, kidney impairment, dehydration, and defective immune system responses. When oral drugs are administered, the efficiency of the drug is to produce a therapeutic effect and the lack of this effect may be due to the medication travelling too quickly through the digestive system, limiting the time that it can be absorbed. Clinicians try to treat the diarrheas by reducing the dosage of medication, changing the dosing schedule, discontinuation of the drug, and rehydration. The interventions to control the diarrhea are not often effective. Diarrhea can have a profound effect on the quality of life because fecal incontinence is one of the leading factors for placing older adults in long term care facilities (nursing homes).[19]
In the latter stages of human digestion, ingested materials are inundated with water and digestive fluids such as gastric acid, bile, and digestive enzymes in order to break them down into their nutrient components, which are then absorbed into the bloodstream via the intestinal tract in the small intestine. Prior to defecation, the large intestine reabsorbs the water and other digestive solvents in the waste product in order to maintain proper hydration and overall equilibrium.[25] Diarrhea occurs when the large intestine is prevented, for any number of reasons, from sufficiently absorbing the water or other digestive fluids from fecal matter, resulting in a liquid, or "loose", bowel movement.[26]
Acute diarrhea is most commonly due to viral gastroenteritis with rotavirus, which accounts for 40% of cases in children under five.[1] In travelers, however, bacterial infections predominate.[27] Various toxins such as mushroom poisoning and drugs can also cause acute diarrhea.
Chronic diarrhea can be the part of the presentations of a number of chronic medical conditions affecting the intestine. Common causes include ulcerative colitis, Crohn's disease, microscopic colitis, celiac disease, irritable bowel syndrome, and bile acid malabsorption.[28]
There are many causes of infectious diarrhea, which include viruses, bacteria and parasites.[29] Infectious diarrhea is frequently referred to as gastroenteritis.[30] Norovirus is the most common cause of viral diarrhea in adults,[31] but rotavirus is the most common cause in children under five years old.[32] Adenovirus types 40 and 41,[33] and astroviruses cause a significant number of infections.[34] Shiga-toxin producing Escherichia coli, such as E coli o157:h7, are the most common cause of infectious bloody diarrhea in the United States.[35]
Campylobacter spp. are a common cause of bacterial diarrhea, but infections by Salmonella spp., Shigella spp. and some strains of Escherichia coli are also a frequent cause.[36]
In the elderly, particularly those who have been treated with antibiotics for unrelated infections, a toxin produced by Clostridioides difficile often causes severe diarrhea.[37]
Parasites, particularly protozoa e.g., Cryptosporidium spp., Giardia spp., Entamoeba histolytica, Blastocystis spp., Cyclospora cayetanensis, are frequently the cause of diarrhea that involves chronic infection. The broad-spectrum antiparasitic agent nitazoxanide has shown efficacy against many diarrhea-causing parasites.[38]
Other infectious agents, such as parasites or bacterial toxins, may exacerbate symptoms.[27] In sanitary living conditions where there is ample food and a supply of clean water, an otherwise healthy person usually recovers from viral infections in a few days. However, for ill or malnourished individuals, diarrhea can lead to severe dehydration and can become life-threatening.[39]
Open defecation is a leading cause of infectious diarrhea leading to death.[40]
Poverty is a good indicator of the rate of infectious diarrhea in a population. This association does not stem from poverty itself, but rather from the conditions under which impoverished people live. The absence of certain resources compromises the ability of the poor to defend themselves against infectious diarrhea. "Poverty is associated with poor housing, crowding, dirt floors, lack of access to clean water or to sanitary disposal of fecal waste (sanitation), cohabitation with domestic animals that may carry human pathogens, and a lack of refrigerated storage for food, all of which increase the frequency of diarrhea ... Poverty also restricts the ability to provide age-appropriate, nutritionally balanced diets or to modify diets when diarrhea develops so as to mitigate and repair nutrient losses. The impact is exacerbated by the lack of adequate, available, and affordable medical care."[41]
One of the most common causes of infectious diarrhea is a lack of clean water. Often, improper fecal disposal leads to contamination of groundwater. This can lead to widespread infection among a population, especially in the absence of water filtration or purification. Human feces contains a variety of potentially harmful human pathogens.[42]
Proper nutrition is important for health and functioning, including the prevention of infectious diarrhea. It is especially important to young children who do not have a fully developed immune system. Zinc deficiency, a condition often found in children in developing countries can, even in mild cases, have a significant impact on the development and proper functioning of the human immune system.[43][44] Indeed, this relationship between zinc deficiency and reduced immune functioning corresponds with an increased severity of infectious diarrhea. Children who have lowered levels of zinc have a greater number of instances of diarrhea, severe diarrhea, and diarrhea associated with fever.[45] Similarly, vitamin A deficiency can cause an increase in the severity of diarrheal episodes. However, there is some discrepancy when it comes to the impact of vitamin A deficiency on the rate of disease. While some argue that a relationship does not exist between the rate of disease and vitamin A status,[46] others suggest an increase in the rate associated with deficiency.[47] Given that estimates suggest 127 million preschool children worldwide are vitamin A deficient, this population has the potential for increased risk of disease contraction.[48]
Malabsorption is the inability to absorb food fully, mostly from disorders in the small bowel, but also due to maldigestion from diseases of the pancreas.
Causes include:[citation needed]