An adenoma that arises from the rectum. The group of rectal adenomas includes tubular, villous, and tubulovillous adenomas, traditional serrated adenomas, sessile serrated adenomas/polyps, and familial adenomatous polyposis. The disease is rectum adenoma (Monarch Disease Ontology id MONDO_0000530). Also known as: adenoma of rectum, adenoma of the rectum, rectal adenoma.