The pelvic cavity is the space where the pelvis encases the internal organs. For women, the pelvic cavity includes many internal organs, such as the uterus, ovaries, fallopian tubes, vagina, bladder, and rectum. If a woman develops gynecological diseases, such as pelvic inflammatory disease, endometriosis, ovarian chocolate cysts, etc., they can cause reactive inflammation in the pelvis, leading to pelvic exudation and pelvic effusion, so pelvic effusion is usually an inflammatory reaction of the pelvis. For men, the pelvic cavity is wrapped with organs such as the rectum, bladder, and prostate. If men develop prostate enlargement, prostate inflammation, prostate tumor, prostate cancer, bladder cancer, or even rectal cancer, this can also reactively lead to pelvic inflammation and exudation, resulting in pelvic effusion.