Pink blood inside the stool, most commonly seen in hemorrhoids, anal fissure, ulcerative colitis, perianal polyps and so on. 1. Hemorrhoids: mostly seen in internal hemorrhoids, bleeding may also be mixed hemorrhoids of the internal hemorrhoid part of the bleeding, may be manifested as blood on the finger or stool dripping blood phenomenon, so it will lead to pink blood. 2. Anal fissure: often because the stool is too dry, in the process of discharge, resulting in the anal part of the skin tear caused by the symptoms. 3. Ulcerative colitis: due to the mucous membrane of the colon is damaged, there is an ulcerated surface, which sometimes leads to the bleeding phenomenon of the ulcerated surface, and with the discharge of stools, pink blood. 4. Perianal polyp: it is an elevated lesion that occurs in the perianal epithelium, which may be caused by chronic inflammatory stimulation, and may sometimes lead to bleeding during defecation. Stool mixed with pink blood, may also be due to other reasons, usually need to go to the hospital to do routine stool examination, colonoscopy, etc. to make a clear diagnosis, follow the doctor’s instructions for treatment.