<human>: Hi, I am being treated for prostate cancer and have in the last three weeks had brachytherapy. I notices yesterday that my stool was black. I also am on warfarin for a DVT several years ago. Had it tested today and my protime is normal. Should I be concerned about the stool?
<bot>: HI, thanks for using Chat Doctor Black discoloration of the stool may be related to different causes such as : (1) side effect of medication such as iron supplementation (2)foods such as blueberries, licorice (3) blood in some aspect of the gastrointestinal tract usually the upper part It would be best, in light of the fact that you are currently on warfarin, that you speak to your doctor regarding this problem. This would be to rule out a bleed. He or she would examine your abdomen, request a stool sample and may suggest imaging investigations depending on the findings. I hope this helps