What causes diarrhea?
Diarrhea occurs because more fluid passes through the large intestine (colon) than that organ can absorb. Normally, stool is 60 to 90% water; diarrhea mainly results when the percentage exceeds 90%. Stool may contain too much water if it travels too quickly through the digestive tract, if certain components of the stool prevent the large intestine from absorbing water, or if water is being secreted by the large intestine into the stool. As a rule, the colon can absorb several times more fluid than is
required on a daily basis. However, when this reserve capacity is overwhelmed, diarrhea occurs.
Rapid transit of stool is one of the most common causes of diarrhea. For stool to have normal consistency, it must remain in the large intestine for a certain amount of time. Stool that leaves the large intestine too quickly is watery. Many medical conditions and treatments can decrease the amount of time that stool stays in the large intestine, including an overactive thyroid (hyperthyroidism) or Zollinger-Ellison syndrome; surgical removal of part of the stomach, small intestine, or large intestine; treatment of ulcers in which the vagus nerve is cut; surgical bypass of part of the intestine; and drugs such as antacids containing magnesium, laxatives, prostaglandins, serotonin, and even caffeine. Many foods, especially those that are acidic, can increase transit. Some people are intolerant of specific foods and always develop diarrhea after eating them. Stress and anxiety are also common causes.
Osmotic diarrhea occurs when certain substances that cannot be absorbed into the bloodstream remain in the intestine. These substances cause excessive amounts of water to remain in the stool, leading to diarrhea. Certain foods (such as some fruits and beans) and hexitols, sorbitol, and mannitol (used as sugar substitutes in dietetic foods, candy, and chewing gum) can cause osmotic diarrhea. Also, lactase deficiency can lead to osmotic diarrhea. (Lactase is an enzyme normally found in the small intestine that converts lactose [milk sugar] to glucose and galactose, so that it can be absorbed into the bloodstream.) When people with lactase deficiency drink milk or eat dairy products, lactose is not digested. As lactose accumulates in the intestine, it causes osmotic diarrhea. The severity of osmotic diarrhea depends on how much of the osmotic substance is consumed. Diarrhea stops soon after the person stops eating or drinking the substance. Blood in the digestive tract also acts as an osmotic agent and results in black, tarry stools (melena). Another cause of osmotic diarrhea is an overgrowth of normal intestinal bacteria or the growth of bacteria normally not found in the intestines. Infection by certain parasites (for example, amebas) can also cause osmotic diarrhea. Antibiotics can cause osmotic diarrhea by destroying the normal intestinal bacteria.
Secretory diarrhea occurs when the small and large intestines secrete salts (especially sodium chloride) and water into the stool. Certain toxins - such as the toxin produced during a cholera infection or during some viral infections - can cause these secretions. Infections by certain bacteria (for example, Campylobacter) and parasites (for example, Cryptosporidium) can also stimulate secretions. The diarrhea can be massive - more than a quart of stool an hour in cholera. A classic example of acute secretory diarrhea is cholera, and is also seen in infections like enterotoxigenic E coli. Chronic secretory diarrhea is seen in celiac sprue, collagenous colitis, VIPoma, carcinoid tumor, and hyperthyroidism. Stimulant laxatives (phenolphthalein, senna, bisacodyl) also cause secretory diarrhea. |
More information on diarrhea
What is diarrhea? - Diarrhea is a condition characterized by frequent bowel movements and feces that are soft or watery, and that may contain blood, pus, or mucus. Severe diarrhea in children can lead to dehydration and death.
What causes diarrhea? - Diarrhea may be caused by infections of the digestive system, medicines such as antibiotics, malabsorption, irritable bowel syndrome, or other factors.
What're the symptoms of diarrhea? - Diarrhea is characterized by frequent loose stools. Patients with diarrhea present with various clinical features depending on the underlying cause.
How is diarrhea diagnosed? - Most cases of acute diarrhea never need diagnosis or treatment. The most useful are stool culture and examination for parasites.
What're the treatments for diarrhea? - Treatment is ideally directed toward correcting the cause; however, the first aim should be to prevent or treat dehydration and nutritional deficiencies.
What's acute diarrhea? - Acute diarrhea is a disorder in which people develop loose stools and increased frequency of stools. Acute diarrhea lasts for a day or two and often stops as suddenly as it started.
Infant diarrhea prevention and treatment - Most acute diarrhea in infants and young children is due to viral gastroenteritis and is usually short-lived. Antibiotics are not routinely prescribed for viral gastroenteritis.
What are the causes of acute diarrhea? - The most common causes of acute diarrhea are infectious agents. Other important causes include food poisoning, medications, inflammatory or ischemic bowel disease.
What is chronic diarrhea? - Chronic diarrhea is defined as loose stool that persists for greater than 1 month. Chronic diarrhea is usually caused by a parasite.
What are the causes of chronic diarrhea? - Chronic diarrhea is frequently due to many of the same things that cause the shorter episodes (infections, medications, etc.).
What is traveler's diarrhea? - Traveler's diarrhea is a term used to describe the diarrhea caused by infection with bacteria, protozoa, or viruses ingested by consuming food or water that has been contaminated.
What are the causes of traveler's diarrhea? - Traveler's diarrhea may be caused by any of several bacteria, viruses, or parasites. Cooks and food handlers may have the germs that cause traveler's diarrhea.
What are the symptoms of traveler's diarrhea? - Nausea, vomiting, borborygmi, abdominal cramps, and diarrhea begin 12 to 72 h after ingesting contaminated food or water.
How is traveler's diarrhea diagnosed? - In some cases, a doctor might be able to identify the infecting organism, which could lead to a specific treatment.
What's the treatment for traveler's diarrhea? - Dehydration is the biggest danger of traveler's diarrhea. In most cases, diarrhea ends within three to five days without antibiotic treatment.
How to prevent traveler's diarrhea? - Many cases of traveler's diarrhea can be prevented. Travelers should dine at restaurants with a reputation for safety and avoid foods and beverages from street vendors. |
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