Lower gastrointestinal bleeding can be caused by various etiologies including hemorrhoids, diverticulitis, neoplasms, and ulcerative colitis. However, a rectal ulcer is rarely caused by lower gastrointestinal bleeding, and an anorectal foreign body is a very rare cause of a rectal ulcer. We report the case of a 48-year-old male patient who presented to the emergency department with massive hematochezia and hypovolemic shock that occurred 5 days after inserting garlic into the rectum for treatment of benign prostate hyperplasia.