Any factor that impairs or blocks the flow of blood from the pelvic veins out of the pelvis can lead to pelvic venous stasis. The female pelvic circulation is very different in terms of anatomy, circulatory dynamics and mechanics compared to men. It is easy to form the cause of pelvic stasis. 1, anatomical factors. The female pelvic circulation is mainly characterized by an increase in the number of veins and a weak structure. Generally two or more veins accompanied by a homonymous artery, there are more anastomotic branches and venous plexus, slow blood flow, such as the pelvis of the intermediate veins uterine veins, vaginal veins and ovarian veins, most of the 2 to 3 veins accompanied by a homonymous artery, ovarian veins and even up to 5-6, forming a trapezoidal venous plexus, curved in the uterine body on both sides of the posterior until they flow through the pelvic rim before the formation of a single Ovarian vein. There are many anastomotic branches between the uterine, tubal, and ovarian veins, and within the fallopian tube tunic, there are anastomotic branches of the uterine and ovarian veins, and they form a circular venous circulation, which then anastomoses with the lateral ovarian venous plexus. The venous plexuses originating from the mucous and muscular layers of the pelvic organs and their subplasma membranes converge to form more than two veins that flow into the thick internal iliac vein. The increase in the number of pelvic veins is to accommodate the slow flow of the pelvic veins. The pelvic veins are thinner than veins in other parts of the body, lack the sheaths of fascia, are inelastic, have mostly no valves, and the valves are often incompetent in some PMSCs. The veins penetrate in the loose connective tissues of the pelvis, and the pelvic veins of women have more blood volume, so it is easy to cause venous stasis in the pelvis, external genitalia, bladder, rectum and perianal veins, resulting in vascular tortuosity, dilatation and stasis. At the same time combined with vulvar, cervical and lower abdominal varicose veins. In addition, the veins of bladder, rectum and genitals are connected with each other, and any one of them can affect the other two systems. 2. Physical factors. Some patients, due to physical factors, have significantly weaker vascular wall tissues, fewer elastic fibers, poor elasticity, and are prone to venous stagnation. 3.Mechanical factors. Because of early marriage and early childbearing, overburdened when their genitals are not fully mature, or not regular intercourse, frequent pregnancy and childbirth are prone to produce pelvic venous stasis, due to the influence of a large number of estrogen and progesterone, coupled with the pressure of the peripheral veins of the uterus, which can cause peripheral venous dilatation of the uterus. Prolonged standing or sedentary position, due to the role of gravity of the uterine body and the bladder filling the body of the uterus to the backward displacement, can also affect the outflow of the pelvic veins. For those who sleep on their backs, most of the pelvic veins are lower than the inferior vena cava, which is not conducive to the outflow of blood from the pelvic veins to the pelvis. Tubal ligation. As the blood supply of fallopian tube is double supply, the artery originates from the tubal branch and isthmus branch of uterine artery, and the funnel part is distributed by the umbrella branch of ovarian artery, which are anastomosed with each other, while the vein partly enters into ovarian plexus and partly enters into cervicovaginal plexus, which creates the characteristics of the fallopian tubal artery and vein going in different directions. In the process of tubal ligation, if the tubal mesosalpinx veins are damaged or localized lesions disrupt the balanced relationship of the blood supply, the dynamics of the pelvic venous circulation will be affected. Obstruction of blood circulation in the mesosalpinx vascular network results in venous varicose veins. It can be considered that the damage or local lesions caused by tubal ligation is one of the main factors of the many factors that occur in pelvic varicose veins. 5.Autonomic function disorder. Many scholars believe that the main symptoms of this syndrome are easy fatigue, lumbar pain, sensual unpleasantness, etc., and the occurrence of insomnia, depression, dysthymia and pelvic venous stasis are closely related, therefore, the autonomic nervous regulation function is out of balance and lead to local pelvic venous stasis. 6.Other factors. Uterine fibroids, chronic pelvic inflammatory disease (especially the formation of tubo-ovarian cysts), lactation, chronic amenorrhea cervicitis, etc., imaging can show pelvic venous stasis image.