Rule out a coagulopathy. The NGT helps differentiate upper from lower GI bleeding. A negative NGT does not rule out an upper GI bleed. The rectal exam is also important. Melena indicates the bleed is proximal to the ileocecal valve.
Maroon stools can be either from a rapid small bowel transit or a colonic bleed.
Hemorrhoids do not imply etiology. Use guaiac cards. Black stools can result from Pepto-Bismol, iron, charcoal, and spinach. Red stools can result from beets. These are preferable if the situation warrants.