Pain in the left buttock is a relatively common clinical condition of anal disease, manifesting as pain and bleeding; as well as prolapsed internal hemorrhoids and difficulty in passing stools. Pain is the most common clinical symptom in anorectology. If the buttock pain is caused by: the first one, anal sinusitis. The second, then consider internal hemorrhoid thrombosis. The third, consider a case of proctitis. The fourth, consider the case of perianal abscess. If the pain is vague, accompanied by a feeling of downward movement and fever, it is anal sinusitis. If the pain is more intense, accompanied by low fever or even generalized fever, it is considered perianal abscess. If there has been bleeding in the stool, prolapsed internal hemorrhoids with pain, it is internal hemorrhoid thrombosis. In clinical practice, it is usually seen in these three cases, and a proctoscopy is basically enough to make a clear diagnosis.