What Causes Chronic Rectal Bleeding?

My husband is 54 and has been bleeding when he has a bowel movement, this has been going on for a few years and is getting worse. This isn't just a little pink color in the toilet, it is really red. Tonight was the first time that I know of that blood came out when he wasn't using the restroom and when thru his underwear on to the bed. He says it's probably just hemorrhoids...