Kids ingesting magnets?

this topic was brought to my attention a while back through the show greys anatomy and i was wondering if anyone knows anything about it. in the show a kid ingested magnets and the doctors had to do surgery to get them out. i want to write a paper about this for college (for a health cl) to bring it to peoples attention but i want to know more details so i can write it correctly. do you know what negative things can occur?