There are various diseases that cause foreign body sensation in the anus, mainly including five conditions: first, anal foreign body, mostly with a clear history of trauma or foreign body insertion, manifesting as a foreign body sensation in the anus, and may be accompanied by anal bleeding or distension and discomfort. Second, hemorrhoids, a common clinical category of rectal perianal disease, manifesting as blood dripping from the anus after the stool, which can be accompanied by a foreign body feeling in the anus and a sense of incomplete defecation. Third, anal papillitis, an acute inflammatory change of the anal papilla, manifested as a foreign body sensation in the anus, accompanied by anal pain, and sometimes visible anal oozing purulent fluid. Fourth, malignant tumor of anal canal, there is often no characteristic clinical manifestation in the early stage, when the disease progresses to the advanced stage, there can be a foreign body feeling in the anus, and can be accompanied by changes in stool characteristics, such as diarrhea or unformed stool. Fifthly, adenoma or polyp of rectum and anal canal, manifested as painless blood in stool, and the adenoma or polyp with tip can be seen to be prolapsed outside the anus during defecation.