There are several reasons why the right ovary may not show up on the ultrasound: 1. There may be a congenital abnormality in the development of the ovary, one side of the adnexa is absent, and there is no right ovary originally, but after all, it is a minority, and it is possible that the right ovary has undergone surgery and has been surgically removed, so it may not show up. 2. The right ovary may be difficult to show under ultrasound because it is wrapped by the surrounding peritoneum or the intestines have changed the original position of the ovary.