Diarrhea

                 

Diarrhea

Diarrhea

An electron micrograph of rotavirus, the cause of nearly 40% of hospitalizations from diarrhea in children under five.[1]

Diarrhea or diarrhoea (from the Greek διάρροια from διά dia "through" and ῥέω rheo "flow") is the condition of having at least three loose or liquid bowel movements each day. It often lasts for a few days and can result in dehydration due to fluid loss. Signs of dehydration often begin with loss of the normal stretchiness of the skin and changes in personality. This can progress to decreasedurination, loss of skin color, a fast heart rate, and a decrease in responsiveness as it becomes more severe. Loose but non watery stools in babies who are breastfed, however, may be normal.^[2]

The most common cause is an infection of the intestines due to either a virus, bacteria, or parasite, a condition known asgastroenteritis. These infections are often acquired from food or water that has been contaminated by stool, or directly from another person who is infected. It may be divided into three types: short duration watery diarrhea, short duration bloody diarrhea, and if it lasts for more than two weeks persistent diarrhea. The short duration watery diarrhea may be due to an infection by cholera. If blood is present it is also known as dysentery.^[2] A number of non-infectious causes may also result in diarrhea including: hyperthyroidism,lactose intolerance, inflammatory bowel disease, a number of medications, and irritable bowel syndrome among other.^[3] In most cases stool cultures are not required to confirm the exact cause.^[4]

Prevention of infectious diarrhea is by improved sanitation, clean drinking water, and hand washing. Breastfeeding for at least six month is also recommended as is vaccination against rotavirus. Oral rehydration solution (ORS), which is clean water with modest amounts of salts and sugar, along with zinc tablets are the treatments of choice.^[2] This treatment 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 breastfeed.^[2] If commercial ORS are not available, homemade solutions may be used.^[5] In those with severe dehydration, intravenous fluids may be required.^[2] Most cases; however, can be managed well with fluids by mouth.^[6] 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.^[4] Loperamide may help decrease the number of bowel movement but is not recommended in those with severe disease.^[4]

About 1.7 to 5 billion cases of diarrhea occur per year.^[2][3] It is most common in developing countries were young children get diarrhea on average three times a year.^[2]Worldwide, as of 2012, it is the second most common cause of deaths in children less than five (0.76 million or 11%).^[2][7] Frequent episodes of diarrhea are also a common cause of malnutrition and the most common cause in those less than five years of age.^[2] Other long term problems that can result include poor physical and intellectual development.

Definition

Types 5–7 on the Bristol Stool Chartindicate diarrhea

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.^[8]

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 Organisation.^[9]

Secretory

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, especiallychloride ions. Therefore, to maintain a charge balance in the lumen, sodium is carried with it, along with water. In this type of diarrhea intestinal fluid secretion is isotonic with plasma even during fasting.^[10] It continues even when there is no oral food intake.

Osmotic

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.^[11] Osmotic diarrhea can also be the result of 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 osmoticlaxatives (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.^[10] In most of these cases, osmotic diarrhea stops when offending agent (e.g. milk, sorbitol) is stopped.

Exudative

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.^[10]

Inflammatory

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^{[clarification needed]} can be found in this type of diarrhea. 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.^{[citation needed]}

Dysentery

If there is blood visible in the stools, it is also known as dysentery. The blood is trace of an invasion of bowel tissue. Dysentery is a symptom of, among others, Shigella,Entamoeba histolytica, and Salmonella.

Differential diagnosis

Diagram of the humangastrointestinal tract.

Diarrhea is most commonly due to viral gastroenteritis with rotavirus, which accounts for 40% of cases in children under five.^[1] (p. 17) Intravelers however bacterial infections predominate.^[12] 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.

Infections

Main article: Infectious diarrhea

There are many causes of infectious diarrhea, which include viruses, bacteria and parasites.^[13] Norovirus is the most common cause of viral diarrhea in adults,^[14] but rotavirus is the most common cause in children under five years old.^[15] Adenovirus types 40 and 41,^[16] andastroviruses cause a significant number of infections.^[17]

Campylobacter spp. are a common cause of bacterial diarrhea, but infections by Salmonella spp., Shigella spp. and some strains ofEscherichia coli are also a frequent cause.^[18]

In the elderly, particularly those who have been treated with antibiotics for unrelated infections, a toxin produced by Clostridium difficile often causes severe diarrhea.^[19]

Parasites do not often cause diarrhea except for the protozoan Giardia, which can cause chronic infections if these are not diagnosed and treated with drugs such asmetronidazole,^[20] and Entamoeba histolytica.^[21][22]

Other infectious agents such as parasites and bacterial toxins also occur.^[12] 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.^[23]

Malabsorption

Main article: Malabsorption

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:

• enzyme deficiencies or mucosal abnormality, as in food allergy and food intolerance, e.g. celiac disease (gluten intolerance), lactose intolerance (intolerance to milk sugar, common in non-Europeans), and fructose malabsorption.
• pernicious anemia, or impaired bowel function due to the inability to absorb vitamin B₁₂,
• loss of pancreatic secretions, which may be due to cystic fibrosis or pancreatitis,
• structural defects, like short bowel syndrome (surgically removed bowel) and radiation fibrosis, such as usually follows cancer treatment and other drugs, including agents used in chemotherapy; and
• certain drugs, like orlistat, which inhibits the absorption of fat.

Inflammatory bowel disease

Main article: Inflammatory bowel disease

The two overlapping types here are of unknown origin:

• Ulcerative colitis is marked by chronic bloody diarrhea and inflammation mostly affects the distal colon near the rectum.
• Crohn's disease typically affects fairly well demarcated segments of bowel in the colon and often affects the end of the small bowel.

Irritable bowel syndrome

Main article: Irritable bowel syndrome

Another possible cause of diarrhea is irritable bowel syndrome (IBS) which usually presents with abdominal discomfort relieved by defecation and unusual stool (diarrhea orconstipation) for at least 3 days a week over the previous 3 months.^[24] Symptoms of diarrhea-predominant IBS can be managed through a combination of dietary changes, soluble fiber supplements, and/or medications such as loperamide or codeine. About 30% of patients with diarrhea-predominant IBS have bile acid malabsorption diagnosed with an abnormal SeHCAT test.^[25]

Other causes

• Diarrhea can be caused by chronic ethanol ingestion.^[26]
• Ischemic bowel disease. This usually affects older people and can be due to blocked arteries.
• Microscopic colitis, a type of inflammatory bowel disease where changes are only seen on histological examination of colonic biopsies.
• Bile salt malabsorption (primary bile acid diarrhea) where excessive bile acids in the colon produce a secretory diarrhea.
• Hormone-secreting tumors: some hormones (e.g., serotonin) can cause diarrhea if excreted in excess (usually from a tumor).
• Chronic mild diarrhea in infants and toddlers may occur with no obvious cause and with no other ill effects; this condition is called toddler's diarrhea.

Pathophysiology

Evolution

According to two researchers, Nesse and Williams, diarrhea may function as an evolved expulsion defense mechanism. As a result, if it is stopped, there might be a delay in recovery.^[27] They cite in support of this argument research published in 1973 which found that treating Shigella with the anti-diarrhea drug (Co-phenotrope, Lomotil) caused people to stay feverish twice as long as those not so treated. The researchers indeed themselves observed that: "Lomotil may be contraindicated in shigellosis. Diarrhea may represent a defense mechanism".^[28]

Diagnostic approach

The following types of diarrhea may indicate further investigation is needed:

• In infants
• Moderate or severe diarrhea in young children
• Associated with blood
• Continues for more than two days
• Associated non-cramping abdominal pain, fever, weight loss, etc.
• In travelers
• In food handlers, because of the potential to infect others;
• In institutions such as hospitals, child care centers, or geriatric and convalescent homes.

A severity score is used to aid diagnosis in children.^[29]

Prevention

A rotavirus vaccine decrease the rates of diarrhea in a population.^[1] New vaccines against rotavirus, Shigella, ETEC, and cholera are under development, as well as other causes of infectious diarrhea.

Probiotics decrease the risk of diarrhea in those taking antibiotics.^[30] In institutions and in communities, interventions that promote hand washing lead to significant reductions in the incidence of diarrhea.^[31]

Management

In many cases of diarrhea, replacing lost fluid and salts is the only treatment needed. This is usually by mouth – oral rehydration therapy – or, in severe cases, intravenously.^[1]Diet restrictions such as the BRAT diet are no longer recommended.^[32] Research does not support the limiting of milk to children as doing so has no effect on duration of diarrhea.^[33] To the contrary, WHO recommends that children with diarrhea continue to eat as sufficient nutrients are usually still absorbed to support continued growth and weight gain and that continuing to eat speeds also recovery of normal intestinal functioning.^[11] CDC recommends that children and adults with cholera also continue to eat.^[34]

Medications such as loperamide (Imodium) and bismuth subsalicylate may be beneficial; however they may be contraindicated in certain situations.^[35]

Fluids

See also: Management of dehydration

A person consuming oral rehydration solution.

Oral rehydration solution (ORS) can be used to prevent dehydration. Standard home solutions such as salted rice water, salted yogurt drinks, vegetable and chicken soups with salt can be given. Home solutions such as water in which cereal has been cooked, unsalted soup, green coconut water, weak tea (unsweetened), and unsweetened fresh fruit juices can have from half a teaspoon to full teaspoon of salt (from one-and-a-half to three grams) added per liter. Clean plain water can also be one of several fluids given.^[11] There are commercial solutions such as Pedialyte, and relief agencies such as UNICEF widely distribute packets of salts and sugar. A WHO publication for physicians recommends a homemade ORS consisting of one liter water with one teaspoon salt (3 grams) and two tablespoons sugar (18 grams) added^[11] (approximately the "taste of tears"^[36]). Rehydration Project recommends adding the same amount of sugar but only one-half a teaspoon of salt, stating that this more dilute approach is less risky with very little loss of effectiveness.^[37] Both agree that drinks with too much sugar or salt can make dehydration worse.^[11][37]

Appropriate amounts of supplemental zinc and potassium should be added if available. But the availability of these should not delay rehydration. As WHO points out, the most important thing is to begin preventing dehydration as early as possible.^[11] In another example of prompt ORS hopefully preventing dehydration, CDC recommends for the treatment of cholera continuing to give Oral Rehydration Solution during travel to medical treatment.^[34]

Vomiting often occurs during the first hour or two of treatment with ORS, especially if a child drinks the solution too quickly, but this seldom prevents successful rehydration since most of the fluid is still absorbed. WHO recommends that if a child vomits, to wait five or ten minutes and then start to give the solution again more slowly.^[11]

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 dehydration. A too rich solution in the gut draws water from the rest of the body, just as if the person were to drink sea water.^[11][38] Plain water may be used if more specific and effective ORT preparations are unavailable or are not palatable.^[38] Additionally, a mix of both plain water and drinks perhaps too rich in sugar and salt can alternatively be given to the same person, with the goal of providing a medium amount of sodium overall.^[11] A nasogastric tube can be used in young children to administer fluids if warranted.^[39]

Eating

WHO recommends a child with diarrhea continue to be fed. Continued feeding speeds the recovery of normal intestinal function. In contrast, children whose food is restricted have diarrhea of longer duration and recover intestinal function more slowly. A child should also continue to be breastfed. The WHO states "Food should never be withheld and the child's usual foods should not be diluted. Breastfeeding should always be continued."^[11] And in the specific example of cholera, CDC also makes the same recommendation.^[34] In young children who are not breast-fed and live in the developed world, a lactose free diet may be useful to speed recovery.^[40]

Medications

While antibiotics are beneficial in certain types of acute diarrhea, they are usually not used except in specific situations.^[41][42] There are concerns that antibiotics may increase the risk of hemolytic uremic syndrome in people infected with Escherichia coli O157:H7.^[43] In resource poor countries, treatment with antibiotics may be beneficial.^[42] However, some bacteria are developing antibiotic resistance, particularly Shigella.^[44] Antibiotics can also cause diarrhea, and antibiotic-associated diarrhea is the most common adverse effect of treatment with general antibiotics.

While bismuth compounds (Pepto-Bismol) decreased the number of bowel movements in those with travelers' diarrhea, they do not decrease the length of illness.^[45] Anti motility agents like loperamide are also effective at reducing the number of stools but not the duration of disease.^[4] These agents should only be used if bloody diarrhea is not present.^[46]

Bile acid sequestrants such as cholestyramine can be effective in chronic diarrhea due to bile acid malabsorption. Therapeutic trials of these drugs are indicated in chronic diarrhea if bile acid malabsorption cannot be diagnosed with a specific test, such as SeHCAT retention.

Alternative therapies

Zinc supplementation benefits children with diarrhea in developing countries, but only in infants over six months old. This supports the World Health Organisation guidelines for zinc, but not in the very young.^[47]

Probiotics reduce the duration of symptoms by one day and reduced the chances of symptoms lasting longer than four days by 60%.^[48] The probiotic lactobacillus can help prevent antibiotic associated diarrhea in adults but possibly not children.^[49] For those who with lactose intolerance, taking digestive enzymes containing lactase when consuming dairy products often improves symptoms

                                           

Disability-adjusted life year for diarrhea per 100,000 inhabitants in 2004.^[50]

  no data

  < 500

  500–1000

  1000–1500

  1500–2000

  2000–2500

  2500–3000

  3000–3500

  3500–4000

  4000–4500

  4500–5000

  5000–6000

  > 6000