The feeling of swelling in the anus may be caused by hemorrhoids, rectal prolapse, perianal abscess and other diseases. 1. Hemorrhoids: the disease can lead to increased venous pressure in the anorectal area of the patient, resulting in venous enlargement, thus forming pressure on the anus, it may show a feeling of anal swelling, which may also be accompanied by pain, itching and other symptoms. 2. Rectal prolapse: due to the accumulation of the rectal wall in the rectal cavity, the patient’s rectal wall is easily prolapsed out of the anus, thus causing a feeling of swelling in the anus, which may be accompanied by itching of the perianal skin, increased frequency of bowel movements or constipation and other symptoms. 3. Perianal abscess: usually due to anal gland infection, resulting in blockage of the anal glands, resulting in anal swelling, may also be accompanied by fever, blood in the stool, as well as perianal itching, pain and other symptoms. The feeling of swelling in the anus may also be caused by other reasons, if the symptoms are serious, you should seek medical advice as soon as possible, after diagnosing the cause of the disease, the doctor will guide the treatment, to avoid delaying the condition.