I don't think bloody stools is a symptom of gastritis. And it is possible for someone to have gastritis and it go away, but usually it takes an acid reducing medication or PPI (ex. aciphex, protonix, Zantac) to get rid of it. Sometimes the reason someone has gastritis is because of a bacteria called H. Pylori, and until you get rid of the bacteria, the gastritis will more than likely linger. H. Pylori can be tested by a breath test or a biopsy when you have an endoscopy.