What risks are associated with an terrible illness when you have rectal bleeding ?

Most are benign: Many of the things that cause rectal bleeding are benign (not cancer) the most common thing is simple hemorrhoids. Still, you should get seen by a doctor to figure out the cause because even though "terrible" things are rare it is still much better to catch them early when they are small. And if they find they are just hemorrhoids you will rest better.

Many risks: Even though most causes of rectal bleeding sre due to benign conditions like hemorrids but there are others which can be as you say terribl, chrinic and in some cases life threatening 1cancer of colon and rectum must be ruled out with high risk patirents with rectal bleeding 2infammatory bowel disease includes crohns disease and ulcerative colitis which can be chronic with morbidity and disabling.