Diarrhea

Risk: The cause of diarrhea in most cases is unknown. Many individuals contract diarrhea through infections (bacterial, parasitic, viral) that usually occur after the ingestion of contaminated food or water. Infections may also be transmitted individual-to-individual through contaminated hands or objects or in some cases through viral droplet infection. Diarrhea may also be caused by anxiety, failure to absorb certain foods, and drugs (including some antibiotics) that interfere with the harmless bacteria normally found in the intestines. Ingestion of magnesium laxatives or antacids, immune disorders such as Crohn's disease and ulcerative colitis, hormone abnormalities, and cancer of the large intestine may result in diarrhea. Diarrhea may accompany disease of small areas of the colon (diverticula), irritable bowel syndrome, fecal impaction, lack of blood and oxygen to portions of the intestines following radiation therapy, and with certain surgical procedures (stomach, small intestine segment). Diarrhea may also be associated with infectious processes outside the gastrointestinal tract, such as pneumonia, urinary tract infection, and pelvic inflammatory disease.

Incidence and Prevalence: Diarrhea is one of the most common illnesses in all age groups and is second only to the common cold as a cause of lost days of work. It is estimated that almost 100 million cases of acute diarrhea occur per year in adults in the US. Adults have about one bout with diarrhea a year. Less than 10% of cases of diarrhea are brought to the attention of a doctor because most individuals use home care effectively. Diarrhea and dysentery (diarrhea that contains blood, pus, or mucus) are common disorders in third-world countries. In industrialized nations, the occurrence of diarrhea mirrors the US experience.

History: Symptoms may include bowel movements that are increased in fluidity, frequency, or volume compared to the individual's usual pattern. Blood, secretions (mucus), or pus may be present in the stool when damage has occurred to the mucous lining of the intestinal tract. Other symptoms often associated with diarrhea include nausea, vomiting, and fever. Individuals may report family or friends with diarrhea or a history of recent travel.

Physical exam: The exam is usually normal, although abdominal tenderness may be present. If diarrhea has occurred for a while, dehydration may be evident with signs of dry mouth, decreased blood pressure, weakness, lethargy, or confusion. Individual may have increased skin pigmentation or inflammation of the tongue (glossitis).

Tests: In most cases of acute diarrhea, laboratory investigation is unnecessary, unrevealing, and does not affect treatment or outcome. Microscopic examination of the stool for white blood cells (leukocytes) distinguishes noninflammatory from inflammatory diarrhea. If leukocytes are present, a stool culture is done to identify the infectious agent. If diarrhea persists for more than 10 days, examinations are done on three consecutive stools to look for eggs (ova) or parasites.

In cases of chronic diarrhea, additional tests may include 24-hour stool collection for weight and quantitative fecal fat to identify a malabsorption process; a stool laxative screen to rule out laxative abuse; and a stool osmolality to rule out lactase deficiency, laxative abuse, or malabsorption syndromes. Routine laboratory tests to rule out malabsorption, anemia, and inflammatory diseases include complete blood count (CBC), serum electrolytes, liver function tests, calcium, phosphorus, albumin, thyroid-stimulating hormone (TSH), total thyroxine (T4), beta-carotene, and prothrombin. In individuals with severe inflammation of the rectum or anus, direct visualization of the sigmoid colon and the entire colon via an instrument inserted into the rectum (sigmoidoscopy and colonoscopy) may be needed. Removal of a small sample of mucous membrane for microscopic analysis (biopsy) is warranted to distinguish infectious diarrhea from ulcerative colitis or ischemic colitis. X-ray studies of the digestive tract using barium to visualize the intestines are useful in detecting abnormal narrowing (strictures) or other anatomic abnormalities beyond the reach of the sigmoidoscope.