What is Diarrhea?

Diarrhea, also spelled diarrhoea, is the condition of having three or more loose or liquid bowel movements per day. It is a common cause of death in developing countries and the second most common cause of infant deaths worldwide.

The loss of fluids through diarrhea can cause dehydration and electrolyte imbalances. In 2009 diarrhea was estimated to have caused 1.1 million deaths in people aged 5 and over and 1.5 million deaths in children under the age of 5. Oral rehydration salts and zinc tablets are the treatment of choice and have been estimated to have saved 50 million children in the past 25 years.

World wide in 2004 approximately 2.5 billion cases of diarrhea occurred which results in 1.5 million deaths among children under the age of five. Greater than half of these were in Africa and South Asia. This is down from a death rate of 5 million per year two decades ago. Diarrhea remains the second leading cause of death (16%) after pneumonia (17%) in this age group.

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.

Osmotic

Osmotic diarrhea occurs when too much water is drawn into the bowels.

This can 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. Osmotic diarrhea can also 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.

It can also be the part of the presentations of a number of medical conditions such as: Crohn's disease or mushroom poisoning.

Infections

There are many causes of infectious diarrhea, which include viruses, bacteria and parasites. Norovirus is the most common cause of viral diarrhea in adults, but rotavirus is the most common cause in children under five years old. Adenovirus types 40 and 41, and astroviruses cause a significant number of infections.

The bacterium campylobacter is a common cause of bacterial diarrhea, but infections by salmonellae, shigellae and some strains of ''Escherichia coli'' (E.coli) are frequent. In the elderly, particularly those who have been treated with antibiotics for unrelated infections, a toxin produced by ''Clostridium difficile'' often causes severe diarrhea.

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 as metronidazole, and '' Entamoeba histolytica''.

Other infectious agents such as parasites and bacterial toxins also occur. 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.

Malabsorption

Malabsorption is the inability to absorb food, mostly in the small bowel but also due to the pancreas.

Causes include celiac disease (intolerance to wheat, rye, and barley gluten, the protein of the grain), 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, including agents used in 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

Another possible cause of diarrhea is irritable bowel syndrome (IBS) which usually presents with abdominal discomfort relieved by defecation and unusual stool (diarrhea or constipation) for at least 3 days a week over the previous 3 months. There is no direct treatment for IBS, however symptoms can be managed through a combination of dietary changes, soluble fiber supplements, and/or medications.

Other causes

Diarrhea can be caused by chronic ethanol ingestion.
Ischemic bowel disease. This usually affects older people and can be due to blocked arteries.
Hormone-secreting tumors: some hormones (e.g., serotonin) can cause diarrhea if excreted in excess (usually from a tumor).