I had a colonoscopy and polyp removal.  In none of my instructions was I advised not to fly following the surgery.  When I arrived in California two days after the procedure and suffered a severe hemorrhage which left me in the hospital for 3.5 days and another colonoscopy to repair it and a month later I'm still anemic and recovering.   A friend's husband who is a Dr. Confirmed that flying was most likely the culprit.  This situation and great inconvenience and expense could have been avoided with better instructions. 
EAST GI