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[dia- + -rrhea]
Passage of loose, unformed stools. In acute diarrhea, the frequency of bowel movements and the volume of fluid lost determine the severity of the illness. In tropical nations, infectious diarrheal illnesses are among the most common causes of disease and death, esp. in children, who become dehydrated easily. Diarrhea in the tropics is typically attributed to contaminated drinking water, inadequate sanitation, or poor hygiene. Worldwide, millions of children die from diarrhea each year. Diarrheal illnesses are common in Western nations as well but tend to be more benign and more effectively managed.
SEE: cholera; SEE: oral rehydration therapy; SEE: viral gastroenteritis
diarrheal (dī-ă-rē′ăl), adj.

Five general mechanisms may cause diarrhea. Excessive secretion, or secretory diarrhea, is usually caused by infectious organisms (such as adenovirus, rotavirus, Vibrio cholerae, Cryptosporidium) or enterotoxins (such as Escherichia coli, Clostridium difficile), which produce excessive secretion of electrolytes and water. More than 500 ml of stool/day is excreted even during fasting. In inflammatory or exudative disorders, infectious organisms (such as Salmonella, Shigella) damage the intestinal mucosa; the stools often contain blood or pus and can be of small volume (dysentery) or large. The diarrhea continues during fasting. Transmission of infectious organisms is most commonly person-to-person or through contaminated water or food. The incubation period and duration of illness vary, depending on the organism involved. The diarrhea may be bloody.

Osmotic diarrhea occurs when highly concentrated substances that cannot be absorbed (such as antacids, lactulose, lactose) pull water from the intestinal wall into the stool. More than 500 ml of stool/day is excreted, but the diarrhea subsides during a fasting state.

Malabsorption of nutrients results in steatorrhea with high osmolarity. The diarrhea is eliminated by fasting, and both osmotic and secretory components are involved. Abnormal intestinal motility resulting from surgical removal of sections of the bowel, diabetic neuropathy, or irritable bowel syndrome produces alternating patterns of diarrhea and constipation.

Frequent watery bowel movements or stools with pus, blood, oils, or mucus are characteristic of diarrhea, as are abdominal cramping, bloating, or rectal discomfort. When volume losses from diarrhea are large, symptoms of dehydration or electrolyte imbalance, such as dizziness, thirst, and prostration, are common.

Fluid replacement is the key to successful management of acute diarrhea and the prevention of its complications. Oral rehydration therapies (ORTs) are inexpensive, safe, and effective tools for volume repletion. Intravenous fluids are more costly. Infectious causes of diarrhea are often managed with antibiotics (such as sulfa drugs or quinolones). Antidiarrheal agents include kaolin derivatives, loperamide, and paregorics. Alternative medicine practitioners advocate herbal remedies such as arrowroot. The management of chronic diarrhea depends on the underlying cause.

The patient is assessed for signs and symptoms of dehydration and metabolic disarray or renal failure, such as headache, lethargy, orthostatic dizziness, decreasing level of consciousness, and compensatory hyperventilation. The frequency, consistency, color, and volume of stools are monitored, and bowel sounds auscultated for changes from normal patterns. Fluid balance, intake and output, and daily weights are also monitored. Prescribed oral or intravenous fluids and electrolyte and nutrient replacements are administered, and the patient's response is evaluated. The anal area is assessed for skin excoriation and gently but thoroughly washed and rinsed after each bowel movement, and protective ointment is applied. Standard precautions are observed for these interventions. Antidiarrheal medications are administered as prescribed. Whenever diarrhea or acute gastroenteritis of unknown cause is encountered, health professionals should consider the possibility of waterborne illness and obtain a drinking water history (such as water sources at home, school, and work, recreational water exposures, travel abroad, use of filtering system).

The spread of infectious diarrhea is prevented by practicing and teaching thorough handwashing and hygiene measures, by using standard precautions and measures of controlling infection in health care facilities, by correctly handling and refrigerating foods at risk for bacterial contamination, by appropriately filtering or treating water supplies, and by reporting diarrheal pathogens to appropriate public health authorities.

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