I recently posted a response to this question. I had one episode 5 years ago and also nearly died. According to my doctors it is uncommon. My internist said that it is a good thing because they would lose a lot of people. I ended up with an ileostomy so there is little chance that I would have that exact problem again. Two hospitals investigated thoroughly and they never were able to determine the cause. My episode involved two blood supplies and not three. I do not have any blood disease, clotting disorder,cancer, Crones disease or ulcerative colitis. My health is perfect now and the high blood pressure problem that I had for about 8 years disappeared. My internist intially was worried and was checking me regularly, but now I have my yearly physical and a sigmoidoscopy every 2-3 years. I am 58 years old, excercise 6 days a week and work 4 days a week. Life is great!