The etiology of hemorrhoids is not completely clear, and may be related to a variety of factors, currently there are mainly the following theories. 1.The theory of submigration of anal cushion It is believed that there is a special layer of tissue under the mucous membrane of the anal canal, formed during fetal life, located in the left, right front and right rear areas of the anal canal, protruding into the anal canal; it consists of veins (or venous sinus), smooth muscle, elastic tissue and connective tissue, called the vascular cushion of the anal canal, referred to as the anal cushion, which plays the role of closing the anal canal and regulating defecation. Under normal conditions, the anal cushion is loosely attached to the muscle wall of the anal canal. During defecation, it is mainly pushed downward by downward pressure, and after defecation, it retracts into the anal canal by its own contraction. After the elastic retraction effect is weakened, the anal cushion is filled with blood and moves down to form hemorrhoids. 2, varicose veins theory that the formation of hemorrhoids is mainly due to venous expansion and stasis. Anatomically speaking, the portal venous system and its branch rectal veins have no venous valves; the walls of the upper and lower rectal plexus are thin and shallow; the submucosal tissue of the terminal rectum is loose; all these factors are likely to cause blood stasis and venous dilatation. The rectal canal is located in the lowermost part of the abdominal cavity, and there are many factors that can cause obstruction of rectal venous reflux, such as long-term sitting and standing, constipation, pregnancy, prostate enlargement, and huge pelvic tumors, etc., which can lead to the formation of hemorrhoids by stasis and dilatation of rectal veins with impaired blood flow. Humans are very prone to blood stasis in the anorectal area due to upright posture, which forms hemorrhoids over time. According to the anatomy and observation of reptiles at home and abroad, no one has been found to suffer from hemorrhoids, which provides a strong evidence for the theory. In addition, long-term alcohol consumption and ingestion of large amounts of irritating food can cause local congestion; perianal infection can cause perivenous inflammation, causing veins to lose elasticity and dilate; malnutrition can cause local tissue atrophy and weakness. All of the above factors can induce the occurrence of hemorrhoids.