Bloody diarrhea suggests inflammatory bowel disease or an infectious origin. Bleeding with rectal pain is seen with anal fissures, hemorrhoids, and rectal ulcers. Chronic constipation suggests hemorrhoidal bleeding. New onset constipation or thin stools suggests a left-sided colonic malignancy. Blood on the toilet paper or dripping into the toilet water after a bowel movement suggests a perianal source.
Blood coating the outside of stool suggests a lesion in the anal canal.
Blood streaking or mixed in with the stool may result from a polyp or malignancy in the descending colon. Maroon colored stools often indicate small bowel and proximal colon bleeding.