Massive bleeding per rectum in a 70 yr old patient is due to

Hemorrhage from a colonic diveiculum is the most common cause of hematochezia in patients > 60years old.Most bleeds are self-limited and stop spontaneously with bowel rest. The lifetime risk of rebleeding is 25%.Acute uncomplicated diveiculitis characteristically presents with fever, anorexia, left lower quadrant pain and obstipation.A complicated diveicular disease is defined as a diveicular disease associated with an abscess or perforation and less commonly with a fistula.Barium enema or colonoscopy should not be performed in acute setting because of the higher risk of colonic perforation associated with insufflation or inseion of barium-based contrast material under pressure. (Ref: Harrison's 18/e p2502)