Diarrhea

Diarrhea or diarrhoea (see spelling differences) is a condition in which the sufferer has frequent watery, loose bowel movements (from the ancient Greek word διαρροή = leakage; lit. "to run through"). In the Third World, diarrhea is the most common cause of death among infants, killing more than 1.5 million per year. Much of the incidence of these deaths in underdeveloped countries 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

This condition can occur as a symptom, disease, 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. 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.

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), Giardia lamblia (lives in drinking 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.

Viruses, particularly rotavirus, are common in children. (Viral diarrhea is probably over-diagnosed by non-doctors). The Norwalk virus is rare.

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 sometime 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.

Chronic diarrhea

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.

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

• Ischaemic 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 colon 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.

Treatment of diarrhea

1. Keep hydrated with properly balanced electrolytes. This is the most appropriate treatment in most cases of diarrhea, even dysentery. Large amounts of electrolytes are found in the sports drinks Gatorade and Powerade, so it is a wise choice to drink these while ill with diarrhea. Consuming large amounts of water unbalanced by dietary electrolytes may result in a dangerous electrolytic imbalance which in rare cases can prove fatal (cf. water poisoning).
2. Try eating more but smaller portions. Eat regularly. Don't eat or drink too quickly.
3. Intravenous fluids or a "drip": Sometimes, especially in children, dehydration can be life-threatening and intravenous fluid may be required.
4. Oral rehydration therapy: Taking a sugar/salt solution, which can be absorbed by the body.
5. Opioids and their analogs should not be used for infectious diarrhea as they are said to prolong the illness and may increase the risk of a carrier state. Opioids are the most effective antidiarrheals available. Their principal method of action is to inhibit peristalsis. Loperamide, also known as Imodium, is the most commonly used antidiarrheal. Loperamide is chemically related to the drug meperidine or Demerol, but does not cross the blood-brain barrier and does not appear to induce tolerance or dependence. Other opioids used to control diarrhea (in increasing order of strength) are: Lomotil (diphenoxylate with atropine); Motofen (difenoxin with atropine); codeine; paregoric (camphorated tincture of opium), opium tincture (laudanum); and morphine. The most potent opioids are generally reserved for chronic diarrhea (e.g., from complications of AIDS).
6. Antibiotics: antibiotics may be required if a bacterial cause is suspected and the patient is medically ill. They are sometimes also indicated for workers with carrier states in order to clear up an infection so that the person can resume work. Parasite-related diarrhea (e.g. giardiasis) require appropriate antibiotics. Antibiotics are not routinely used, as the cause is rarely bacterial and antibiotics may further upset intestinal flora and worsen rather than improve the diarrhea. Clostridium difficile-associated diarrhea and pseudomembranous colitis is often caused by antibiotic use.
7. Dietary manipulation: in particular, patients with celiac disease should avoid wheat products. Patients with Irritable Bowel Syndrome can make dietary changes to prevent the over-reaction of their gastrocolic reflex that results in diarrhea. Having soluble fiber foods and supplements, substituting soy or rice products for dairy, being careful with fresh fruits and vegetables that are high in insoluble fiber, and eating regular small amounts can all help to lessen the symptoms of IBS. Foods and beverages to be avoided or minimized include red meat, oily or fatty (and fried) products, dairy (even when there is no lactose intolerance), solid chocolate, coffee (regular and decaffeinated), alcohol, carbonated beverages (especially those also containing sorbitol) and artificial sweeteners. Several of the most common dietary triggers are well-established by clinical studies at this point; research has shown that IBS patients are hypersensitive to fats, insoluble fibers, and fructose .
8. Hygiene and isolation: Hygiene is important in limiting spread of the disease.
9. It is claimed that some fruit, such as bananas, mangoes, papaya, guava and pineapple may have positive effects for this condition . Bananas have the merits of being easily obtainable, and they are unlikely to have any other significant unwanted side effects. Bananas and mangoes are high in soluble fiber, which can help regulate water content in the bowel and alleviate diarrhea. Mucilage, which can be obtained in capsule form, may be helpful for the same reason. Mucilage can also be used as cereal for babies, as it is easily digested. The high acid content of pineapple may make this food a bad choice for people suffering from chronic diarrhea.
10. A common non-pharmaceutical based treatment is to ingest only clear liquids for 24 hours (sports drinks, soup broth, popsicles, jello, ginger ale) followed by the slow introduction of a bland diet often described by the mnemonic BRAT for Bananas, Rice, Applesauce, and Toast.

See also

• Constipation
• 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