Diarrhea

File:Bristol Stool Chart.png

Types 5-7 on the Bristol Stool Chart are often associated with diarrhea

Diarrhea (in American English) or diarrhoea (in British English) is a generally unpleasant condition in which the sufferer has frequent watery, loose bowel movements (from the ancient Greek word διαρροή = leakage; literally meaning "to run through").

Acute infectious diarrhea is a common cause of death in developing countries (particularly among infants), accounting for 5 to 8 million deaths annually. Much of the incidence of these deaths is due to the lack of adequate safe water and lack of sewage treatment capacity; the separation of drinking water from contaminated sewage is also a major issue.

Causes

Diagram of the human gastrointestinal tract.

This condition can occur as a symptom of infection, allergy, food intolerance, foodborne illness and/or extreme excesses of Vitamin C and/or magnesium and may be accompanied by abdominal pain, nausea and vomiting. Temporary diarrhea can also result from the ingestion of laxative medications or large quantities of certain foods like prunes with laxative properties. There are other conditions which involve some but not all of the symptoms of diarrhea, and so the formal medical definition of diarrhea involves defecation of more than 200 grams per day (though formal weighing of stools to determine a diagnosis is never actually carried out).

Diarrhea occurs when insufficient fluid is absorbed by the colon. As part of the digestion process, or due to fluid intake, food is mixed with large amounts of water. Thus, digested food is essentially liquid prior to reaching the colon. The colon absorbs water, leaving the remaining material as a semisolid stool. If the colon is damaged or inflamed, however, absorption is inhibited, and watery stools result.

Diarrhea is most commonly caused by viral infections or bacterial toxins. In sanitary living conditions and with ample food and water available, an otherwise healthy patient typically recovers from the common viral infections in a few days and at most a week. However, for ill or malnourished individuals diarrhea can lead to severe dehydration and can become life-threatening without treatment.

Diarrhea can also be a symptom of more serious diseases, such as dysentery, cholera, or botulism, and can also be indicative of a chronic syndrome such as Crohn's disease. Though appendicitis patients do not generally have diarrhea, it is a common symptom of a ruptured appendix. It is also an effect of severe radiation sickness.

Diarrhea can also be caused by dairy intake in those who are lactose intolerant.

Symptomatic treatment for diarrhea involves the patient consuming adequate amounts of water to replace that loss, preferably mixed with electrolytes to provide essential salts and some amount of nutrients. For many people, further treatment is unnecessary. The following types of diarrhea generally indicate medical supervision is desirable:

• Diarrhea in infants;
• Moderate or severe diarrhea in young children;
• Diarrhea associated with blood;
• Diarrhea that continues for more than 2 weeks;
• Diarrhea that is associated with more general illness such as non-cramping abdominal pain, fever, weight loss, etc;
• Diarrhea in travelers, since they are more likely to have exotic infections such as parasites;
• Diarrhea in food handlers, because of the potential to infect others;
• Diarrhea in institutions such as hospitals, child care centers, or geriatric and convalescent homes.

Mechanism

To expel the contents of the lower digestive tract, the fluidity of the contents of the small and large intestines is increased. Active transport of Na⁺ back into the gut initiates a reverse sodium transport. This causes both Cl^- and HCO₃ to follow passively, as well as water. Now in the intestines, the water dilutes toxins as well as triggering contractions of the intestine due to increase in intestinal distension. These contractions push the contents of the lower GI tract towards and out of the anal canal. Medications such as loperamide are designed to prevent such contractions in response to the distension, and should not be used to prevent diarrhea. Such inhibition actually prolongs the infection or irritation, and can cause a worsening over time because the evacuation of the bowel contents has been delayed.

Types of Diarrhea

There are at least four types of diarrhea: secretory diarrhea, osmotic diarrhea, motility-related diarrhea, and inflammatory diarrhea.

Secretory diarrhea

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 form of this type of diarrhea is a cholera toxin that stimulates the secretion of anions, especially Chloride ions. Therefore, to maintain a charge balance in the lumen, sodium is carried with it, along with water.

Osmotic diarrhea

Osmotic diarrhea occurs when there is a loss of water due to a heavy osmotic load. This can occur when there is maldigestion (e.g., pancreatic disease or Coeliac disease), where the nutrients are left in the lumen, which pulls water into the lumen.

Motility-related diarrhea

Motility-related diarrhea occurs when the motility of the gastrointestinal tract is abnormal. If the food moves too quickly, there is not enough contact time between the food and the membrane, meaning that there is not enough time for the nutrients and water to be absorbed. This can follow a vagotomy or diabetic neuropathy.

Inflammatory diarrhea

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. It can be caused by bacterial infections, viral infections, parasitic infections, or autoimmune problems such as inflammatory bowel disease.

Acute diarrhea

This may be defined as diarrhea that lasts less than 4 weeks, and is also called enteritis.

This can nearly always be presumed to be infective, although only in a minority of cases is this formally proven.

With cases of acute diarrhea, it is often reasonable to reassure a patient, ensure adequate fluid intake, and wait and see. In more severe cases, or where it is important to find the cause of the illness, stool cultures are instituted.

The most common organisms found are Campylobacter (an organism of animal origin), Salmonella (also often of animal origin), Cryptosporidium (animal origin), and Giardia lamblia (lives in water). Shigella (dysentery) is less common, and usually human in origin. Cholera is rare in Western countries. It is more common in travelers and is usually related to contaminated water (its ultimate source is probably sea water). Escherichia coli is probably a very common cause of diarrhea, especially in travelers, but it can be difficult to detect using current technology. The types of E. coli vary from area to area and country to country. Clostridium difficile is considered the most common cause of infectious diarrhea in hospitalized patients worldwide.[1]

Viruses, particularly rotavirus, are common in children. (Viral diarrhea is probably over-diagnosed by non-doctors). Norwalk virus can also cause these symptoms.

Toxins and food poisoning can cause diarrhea. These include staphylococcal toxin (often from milk products due to an infected wound in workers), and Bacillus cereus. Often "food poisoning" is really Salmonella infection. Diarrhea can also be caused by ingesting foods that contain indigestible material, for instance, escolar and olestra.

Parasites and worms sometimes cause diarrhea but are often accompanied by weight loss, irritability, rashes or anal itching. The most common is pinworm (mostly a nuisance rather than a severe medical illness). Other worms, such as hookworm, ascaria, and tapeworm are more medically significant and may cause weight loss, anemia, general unwellness and allergy problems. Amoebic dysentery due to Entamoeba histolytica is an important cause of bloody diarrhea in travelers and also sometimes in western countries. It requires appropriate and complete medical treatment.

Infective diarrhea

It is not uncommon for diarrhea to persist. Diarrhea due to some organisms may persist for years without significant long term illness. More commonly the diarrhea slowly ameliorates but the patient becomes a carrier (harbors the infection without illness). This is often an indication for treatment, especially in food workers or institution workers.

Parasites (worms and amoeba) should always be treated. Salmonella is the most common persistent bacterial organism in humans.

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Malabsorption

These tend to be more severe medical illnesses. Malabsorption is the inability to absorb food, mostly in the small bowel but also due to the pancreas.

Causes include celiac disease (intolerance to gluten, a wheat product), lactose intolerance (Intolerance to milk sugar, common in non-Europeans), fructose malabsorption, pernicious anemia (impaired bowel function due to the inability to absorb vitamin B12), loss of pancreatic secretions (may be due to cystic fibrosis or pancreatitis), short bowel syndrome (surgically removed bowel), radiation fibrosis (usually following cancer treatment), and other drugs such as chemotherapy.

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

Irritable Bowel Syndrome. Symptoms defining IBS: abdominal discomfort or pain relieved by defecation and unusual stool (diarrhea or constipation or both) or stool frequency, for at least 3 days a week over the previous 3 months. IBS symptoms can be present in patients with a variety of conditions including food allergies, infective diarrhea, celiac, and inflammatory bowel diseases. Treating the underlying condition (celiac disease, food allergy, bacterial dysbiosis, etc.) usually resolves the diarrhea. IBS can cause visceral hypersensitivity. While there is no direct treatment for undifferentiated IBS, symptoms, including diarrhea, can sometimes be managed through a combination of dietary changes, soluble fiber supplements, and/or medications.

Other important causes

• Ischemic bowel disease. This usually affects older people and can be due to blocked arteries.
• Bowel cancer: Some (but not all) bowel cancers may have associated diarrhea. Cancer of the large intestine is most common.
• Hormone-secreting tumors: some hormones (e.g. serotonin) can cause diarrhea if excreted in excess (usually from a tumor).
• Bile salt diarrhea: excess bile salt entering the colon rather than being absorbed at the end of the small intestine can cause diarrhea, typically shortly after eating. Bile salt diarrhea is a possible side-effect of gallbladder removal. It is usually treated with cholestyramine, a bile acid sequestrant.

Alcohol

Chronic diarrhea can be caused by chronic ethanol ingestion . Consumption of alcohol affects the body's capability to absorb water - this is often a symptom that accompanies a hangover after a heavy drinking session. The alcohol itself is absorbed in the intestines and as the intestinal cells absorb it, the toxicity causes these cells to lose their ability to absorb water. This leads to an outpouring of fluid from the intestinal lining, which is in turn poorly absorbed. The diarrhea usually lasts for several hours until the alcohol is detoxified and removed from the digestive system. Symptoms range from person to person and are influenced by both the amount consumed as well as physiological differences. Alcohol-induced diarrhea is often accompanied by "the follow through" where a feeling that the patient is going to break wind (flatuence) instead becomes an uncontrolled episode of diarrhea.

See also

• Feces
• Drinking water
• The Diarrhea Song

External links

• Reducing deaths from diarrhoea through oral rehydration therapy. 1: Bull. World Health Organ. 2000;78(10):1246-55.
• Travelers' Diarrhea
• Rehydration Project