Large quantities of water are secreted into the gastrointestinal tract, but almost all this fluid is reabsorbed. Severe diarrhea results in the loss of large quantities of fluid and electrolytes. Saunders CPNRE prep guide, pg 79.
An excess accumulation of fluid in the interstitial spaces; occurs as a result of alterations in oncotic pressure and hydrostatic pressure, capillary permeability, and lymphatic obstruction. Saunders pg 78.