New observations in the sonographic evaluation of intrauterine contraceptive devices.

The in vitro sonographic appearance of the four currently available intrauterine contraceptive devices (IUDs) now used in the United States and Canada were analyzed and compared with in vivo scans. While plastic IUD limbs demonstrated entrance-exit echoes in all scan planes, copper IUDs showed posterior reverberation when optimal gain settings were used. Regardless of the transducer used, posterior acoustic shadowing was only seen when IUD limbs were scanned perpendicular to their long axis and at the junction of long and short limbs. The authors feel that these refined ultrasound characteristics will be helpful in accurately identifying IUDs within the uterus.