How Can Stomach Infection Be Treated?

So, my son has a stomach bug... getting sick for 24 hours... roughly every 1/2 hour through last night... less frequently during the day, but still uncomfortable (to this point, perfectly normal). However, this last round of vomit was bright green. He did have some honey and water and about 2 cheerios. My concern is that as an infant he was born with a web in his duodenum and had mal rotated intestines. As of his last annual check up with the surgeon (when he was about 4) the surgeon said the only symptom to be concerned about is bright green vomit. Is this a moment to be concerned or should I wait and see if the bug continues to run its course? (He s 12).