Female rectal fossa fluid dark area generally refers to the return of pelvic ultrasound examination, suggesting the presence of fluid in the uterorectal fossa, may be physiological fluid, but also pathological fluid, it is recommended that if the patient has the above situation, go to the hospital under the guidance of the doctor treatment. 1. Physiologic effusion: generally refers to the effusion formed when the follicle ruptures and flows into the rectal fossa during the ovulation period of women; or the effusion formed due to the normal secretion of intestinal fluids from the intestinal tract flowing into the rectal fossa. 2. Pathologic effusion: (1) pelvic inflammation: inflammatory exudate, because it can not be absorbed by the body, and then flow to the rectal fossa; in addition, pelvic malignant tumors can also lead to obstruction of lymphatic reflux, appearing in the case of ascites flow to the rectal fossa and the formation of effusion. (2) Tubal pregnancy rupture abortion: ultrasonography can also be seen in the uterorectal fossa there is a liquid dark area, the patient often has a transient history of menopause, and there are sudden onset of severe pain in the lower abdomen, abnormal bleeding in the vagina. (3) Endometriosis: with symptoms of bleeding during the menstrual cycle, fluid may be present in the rectal fossa of the uterus.