There are many causes of lower limb lymphedema, mainly as follows: 1. primary lymphedema: the cause is still unclear; 2. secondary lymphedema: there are more causes, such as venous edema, breast cancer, gynecological tumors, etc., which damage lymphatic vessels and cause lower limb lymphedema; the incidence of lower limb lymphedema caused by bladder cancer and rectal cancer is less than that of gynecological tumors, but it can cause lymphedema in the perineum and abdomen; trauma, heart disease and infection can cause lower limb edema, which needs to be judged according to disease symptoms and clinical manifestations.