There are many reasons why there is a bag on top of the anus: the first one is more common is mixed hemorrhoids combined with thrombosis, mixed hemorrhoids are varicose veins, when the abdominal pressure increases or constipation, the hemorrhoid veins swell, hemorrhoid vein stasis is easy to form a mass, touch with pain, purple color, generally pain is heavy. Second, if the anal gland is infected and spreads along the skin of the anal canal, a perianal abscess can easily appear, and a hard mass can be felt in the perianal area, which is painful to touch. Thirdly, if the patient had anal fissure in the past, long-term diarrhea will easily cause infection of the fissure wound, which will lead to abscess, and perianal ultrasound can also make a clear diagnosis. Fourthly, if a swelling with hard texture and cauliflower-like surface is seen around the anus, the possibility of rectal anal cancer cannot be completely ruled out, and pathological examination should be performed in time to make a clear diagnosis.