Vomit - I know, gross but what does it mean when there's no apparent reason

magtree10

So my little one went through his re-circ, had a catheter, got that out but got a UTI and was on meds.  He started throwing up close to the last day of meds so the night before we decided to stop because it seemed to make him sick.  Now, a week later, or so there's been a couple times where he's throw  up and I can't figure out why. 

 So I guess the question is, for al my fellow one out there is - can LOs throw up for no reason?