Definition
To most persons, diarrhea means an increased frequency or softer consistency of bowel movements; however, the medical definition is more exact than this. Diarrhea best correlates with an increase in stool weight; stool weights above 300 g per day generally indicates diarrhea. This is mainly due to excess water, which normally makes up 60-85% of fecal matter. In this way, true diarrhea is distinguished from diseases that cause only an increase in the number of bowel movements (hyperdefecation), or incontinence (involuntary loss of bowel contents).
Diarrhea is also classified by physicians into acute, which lasts one to two weeks, and chronic, which continues for longer than 2-3 weeks. Viral and bacterial infections are the most common causes of acute diarrhea.
Description
In many cases, acute infectious diarrhea is a mild, limited annoyance. However, acute infectious diarrhea has a huge impact worldwide, causing over five million deaths per year. While most deaths are among children under five years of age in developing nations, the impact, even in developed countries, is considerable. For example, over 250,000 persons are admitted to hospitals in the United States each year because of diarrhea. Rapid diagnosis and proper treatment can prevent much of the suffering associated with this illness.
Chronic diarrhea also has a considerable effect on health, as well as on social and economic well being. Patients with celiac disease, inflammatory bowel disease, and other prolonged diarrheal illnesses develop nutritional deficiencies, which diminish growth and immunity. They affect social interaction and result in the loss of many working hours.
Causes & symptoms
Diarrhea occurs because more fluid passes through the large intestine (colon) than can be absorbed. 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.
Diarrhea is caused by infections or illnesses that either lead to excess production of fluids or prevent absorption of fluids. Also, certain substances in the colon, such as fats and bile acids, can interfere with water absorption and cause diarrhea. In addition, rapid passage of material through the colon can cause diarrhea. Symptoms related to diarrheal illness are often those associated with any injury to the gastrointestinal tract, such as fever, nausea, vomiting, and abdominal pain. All or none of these may be present depending on the cause of diarrhea. The number of bowel movements can vary with up to 20 or more per day. In some patients, blood or pus is present in the stool. Bowel movements may contain undigested food material.
The most common causes of acute diarrhea are infections (the cause of traveler’s diarrhea), food poisoning, and medications. Medications are a frequent and often overlooked cause, especially antibiotics and antacids. Both prescription and over-the-counter medications can contain additives, such as lactose and sorbitol, which will produce diarrhea in sensitive persons. Less often, various sugar-free foods, which sometimes contain poorly absorbable materials, cause diarrhea. Review of allergies or skin changes may also point to a cause.
Chronic diarrhea is frequently due to many of the same things that cause the shorter episodes (infections, medications, etc.); symptoms just last longer. Some infections can become chronic. This occurs mainly with parasitic infections (such as Giardia), or when patients have altered immunity (such as AIDS).
The following are the more usual causes of chronic diarrhea:
- AIDS
- Colon cancer and other bowel tumors
- Endocrine or hormonal abnormalities (thyroid, diabetes mellitus, etc.)
- Food allergy
- Inflammatory bowel disease (Crohn’s disease and ulcerative colitis)
- Lactose intolerance
- Malabsorption syndromes (celiac and Whipple’s disease)
- Other (alcohol, microscopic colitis, radiation, surgery).
The major effects of diarrhea are dehydration, malnutrition, and weight loss. Signs of dehydration can be hard to notice but include thirst, dry mouth, weakness or lightheadedness (particularly if worsening on standing), urine darkening, or a decrease in urination. Severe dehydration leads to changes in the body’s chemistry and could become life threatening. Dehydration from diarrhea can result in kidney failure, neurological symptoms, arthritis, and skin problems.
