difficult to judge but if you have any doubt a quick X-ray will tell you.... the only pain is the wait in A&E (especially if he has a bug, that will not be nice) but on the other hand, if he has a bug and is sick for 2-3 days, you will never be able to relax thinking it's the batteries... difficult one but i think i would take the few hours in A&E waiting (mind you, you are not in London so might be much quicker) instead of a whole night thinking it over and over...