Anatomically, the superior rectal vein in the body appears to be a long-stroke vessel and lacks a venous valve that would prevent venous blood from flowing back. Therefore, the blood in the vessel can produce downward fluid hydrostatic pressure. In addition, the pressure in the abdomen increases when defecating, and over time the distal rectal veins can expand to form hemorrhoids. There are three thickened areas on the surface of the lower rectum and upper anal canal, known as the “anal vascular lining”, consisting of blood vessels, smooth muscle, elastic fibers and structural tissue. When normal, this vascular liner is only loosely attached to the muscle ring under it, and when the muscle ring relaxes during defecation, the vascular liner is turned outward toward the anal opening and cannot be completely reset, which will become hemorrhoids in the long run. Some people have abnormal contraction function of the anal opening muscles, making the anal opening narrow and pressure increase, and must increase the force of defecation to discharge the stool. This affects the normal function and process of defecation, increasing intra-abdominal pressure, venous stasis, and the formation of hemorrhoids.