What can cause rectal bleeding?. my sister is 90 years old and has not had any prior warning when suddenly she passed a significent amount of blood along with clots. she is a healthy woman who has not had to take medicine until age 87. in the last couple

Things : Things that can cause rectal bleeding: diverticulosis, anal fissure, hemorrhoids, cancerous colon tumor, arterial-venous malformation, ischemic bowel, or ulcer.

At age 90: It can not be anything good!. Can be everything from hemorrhoids(low liklihood with clots) to colon tumor or diverticular bleed, to upper GI source such as ulcer or tumor. Being 90 makes her more fragile and can not tolerate major blood loss acutely. Get her to an er or her doctor immediately. Acute major blood loss in an elderly patient can cause acute cardiac events and death. Do not delay or w.