information:extraction, stylistic:style_transfer, structural:summarization
Physiological basis

Fluid from the body enters the intestinal lumen during digestion. This fluid is isosmotic with the blood and contains a high quantity, about 142 mEq/L, of sodium. A healthy individual secretes 2000–3000 milligrams of sodium per day into the intestinal lumen. Nearly all of this is reabsorbed so that sodium levels in the body remain constant. In a diarrheal illness, sodium-rich intestinal secretions are lost before they can be reabsorbed. This can lead to life-threatening dehydration or electrolyte imbalances within hours when fluid loss is severe. The objective of therapy is the replenishment of sodium and water losses by ORT or intravenous infusion.