There are many causes of anechoic areas in the pelvis. If the anechoic area is in the ovary, it could be a normal follicle, or it could be a corpus luteum cyst or a tumor of the ovary. If it is in the fallopian tubes, it could be hydrosalpinx. If it is present in the periphery of the uterus in the form of an echogenic zone, it indicates a pelvic effusion. If it is an echogenic zone in the pelvis, it could also be a tumor of the mesentery, a cystic tumor of the retroperitoneum, all of these conditions are possible. It is important to determine the area of the echogenic zone and the reason for its appearance based on a gynecological examination or MRI.