Thank you for the query.
It is very good you have upper GI performed as Ferros you are taking can cause peptic ulcer
. But it is quite often that Ferros causes black stools and there is nothing wrong in it. So I suggest you to stop taking Ferros and see if your stools color will turn normal. If so, this is the reason, if not, colonsocopy instead of CT angiography
should be performed.
Hope this will help.