causes of bright red blood rectal bleeding
1 Rectal bleeding is the passage of blood through the anus. 2  Rectal bleeding may be red, maroon, black, or occult. 3  The common causes of rectal bleeding include anal fissure, hemorrhoids, diverticulosis, colon cancer and polyps, post-polypectomy, angiodysplasias, colitis proctitis, and Meckel's diverticula.