If the ovaries are not clearly visible through ultrasound examination, the following reasons are common in clinical practice: 1. The ovaries have declined in function, so it is difficult to find ovaries that have become smaller and harder through ultrasound examination. 2. 4. Because of abnormal ovarian location, for example, because of pelvic inflammation or for other reasons, the ovaries are located at the back of the uterus, so the ovaries are often not visible when doing ultrasound, and tissue may be seen in the back wall of the uterus, which is recommended for further clinical examination.