Why does gastritis sometimes causes diarrhea?

Unable to do job: Viral gastroenteritis is the most common cause of self limited diarrhea. Gastritis or inflamation of stomach can also be caused by virus preventing the stomach and intestinal tract from doing its job effectively leading to diarrhea. Another possibility is autoimmune gastritis that can cause diarrhea but more chronic. Other causes of gastritis usually do not cause self limiting diarrhea.