Dehydration: Excessive loss of body water. Diseases of the gastrointestinal tract that cause vomiting or diarrhea may lead to dehydration. There are a number of other causes of dehydration including heat exposure, prolonged vigorous exercise, kidney disease, and medications that cause voiding (diuretics).
One clue to dehydration is a rapid drop in weight. A loss of over 10% (15 pounds in a person weighing 150 pounds) is considered severe.
Symptoms and signs of dehydration include increasing thirst, dry mouth, weakness or lightheadedness (particularly if worse on standing), and a darkening of the urine or a decrease in urination. Severe dehydration can lead to changes in the body's chemistry and kidney failure which may be life-threatening.
Dehydration due to diarrhea is a major cause of morbidity (disease) and mortality (death) in children. The young child has a more rapid turnover of body fluids than an adult. In rehydrating a child, there is less margin for error than for an adult. The younger the child, the more careful the rehydration must be. Cases that demand particular attention to detail are those in which organ function (especially skin, heart, brain, or kidney) is critically compromised. Overhydration may be as serious as severe dehydration in children and rehydration should therefore be done under medical supervision.