what kind of coin? a 50 cent piece or a quarter may be more problematic than a dime but basically a coin will usually pass harmlessly. the only way to be sure if a child swallowed a coin is with an abdominal x-ray but more recently i saw someone use a metal detector (the kind used for searching for coins on a beach). assuming he is well. not vomiting passing stools. the coin may emerge in a day or so (yes you need to look and probe around to see if you find a coin. not a pleasant job but one that only a parent can do). if he is having gastrointestinal issues consulting his medical provider is prudent. i once x-rayed a child with a half-dozen coins in the gi tract. it must have sounded like a slot machine when he went to the toilet!
should i be worried if my 5 yr old has possibly swallowed a coin? or is his gi tract large enough for it to just pass?