What is the basic mechanism of all diarrheal diseases?
Diarrhea is due to the incomplete absorption of fluid from luminal contents. Normal stools are approximately 75% water and 25% solids. Normal fecal water output is approximately 60 to 80 mL per day. An increase of fecal water output of 50 to 100 mL is sufficient to cause loosening of the stool. This volume represents approximately 1% of the fluid load entering the upper intestine each day; thus malabsorption of only 1% to 2% of fluid entering the intestine may be sufficient to cause diarrhea