Mild diarrhea is the passage of a few loose or mushy BMs.
Severe diarrhea is the passage of many watery BMs.
The best indicator of the severity of the diarrhea is its frequency. Green bowel movements are also a sign of severe diarrhea. The main complication of diarrhea is dehydration from the loss of too much body fluid. The main goal of diarrhea treatment is to prevent dehydration. Sometimes it is caused by bacteria or parasites.