Why a maroon steak in my stool?

I'm 44 and once every few months or so I get a dark maroon streak in my stool. (Maybe as infrequently as every 6 months.) In a past physical they found blood in my stool and I saw a specialist who said the cause was internal hemmoroids. Any way this is caused by eating cranberry sauce? I seem to recall that I usually have cranberry sauce a day or two prior to this happening.