If bb 肚呵, then don't give him milk (though breast milk and soya milk should be ok - better check with your doctor). My baby had quite serious 肚呵 a few months back and I stopped his normal milk and gave him soya milk instead for almost a week.
Also, remember to ensure baby drinks plenty of water to prevent dehydration. If baby has no appetite, make the congee slightly more watery, and remember no fruits (but you can give mashed apple, because apple can reduce 肚呵) and no vegetable for now.
My BB also suffered from 腸胃炎 also since last Saturday. The doctor suggested him to take O-Lac (by Meadjohnson) milk powder and it is OK for my BB. Besides, I gave him plain congee and bread for the whole week. Hope you BB recover soon !!