Anal contraction and distension can be caused by hemorrhoids, perianal diseases and constipation and other factors. 1. hemorrhoids: hemorrhoids in the anus, there can be anal contraction and distension of the performance, hemorrhoids are formed by the perianal rectal mucous membrane venous flexure of the veins of the veins, when eating too much spicy stimulating food or long-term smoking and drinking alcohol, can be stimulated perianal mucous membranes, which can cause the local nerves to be stretched, and cause perianal contraction and distension of the performance. 2. Perianal disease: when the occurrence of anal fissure, anal fistula and perianal abscess and other diseases, can cause fistula or pus cavity around the anus and other changes, when the stool through the stimulation of the local, can cause the anus to contract and swell. 3. constipation: daily dietary habits are not scientific, dietary fresh fruits and vegetables and other foods eat less, or intake of too much spicy and stimulating food, can lead to constipation, difficult to defecate and pain and other manifestations, can be stimulated locally to cause anal contraction and distension of the symptoms. When the anal contraction and distension should be timely medical treatment, under the guidance of the doctor to actively carry out appropriate treatment, help early relief of discomfort symptoms.