The terms volume depletion or hypovolemia (a condition in which extracellular fluid is lost) and dehydration (a condition in which pure water loss occurs) are used interchangeably. The most common cause of dehydration is diarrheal illness, which results in 2.5 million deaths annually.[1] [2] [3] [4] Gastroenteritis causes over 200,000 hospital admissions and over 1.5 million outpatient visits every year in the United States. Although not a leading cause of death in the United States, gastroenteritis and related disorders result in a substantial amount of morbidity and generate significant health care costs.