What is the estimated incidence of IUD embedment?
Ultrasound evaluation of IUD placement is indicated for bleeding, pain, or missing strings. Of symptomatic patients, displacement of IUD within the uterine cavity can occur in 25% of patients, while embedment in the endometrium or myometrium that does not extend past the serosa, can occur in 18% of patients. Less common but more severe, uterine perforation rates by an IUD range from 0.3-2.6 per 1,000 insertions.
What are the risk factors for IUD embedment and perforation?
Breast-feeding and post-partum status of less than 36 weeks from delivery are associated with an increased risk of uterine perforation in patients with IUDs. Release of prolactin and oxytocin while breast-feeding cause uterine contraction and low levels of estrogen cause the uterus to shrink. The risk of perforation can remain increased for up to 6 months after delivery. The type of IUD (Levonorgestrel-releasing vs. Copper) is not a contributing risk factor.
Which imaging modalities are best for identifying misplaced IUDs?
Transvaginal ultrasound is used to assess IUD placement and locate IUD in instances that strings are not visualized. Copper IUDs are highly echogenic and produce a ring-down artifact when viewed in the transverse plane. Levonorgestrel-releasing IUDs are less apparent than Copper IUDs on ultrasound and are best visualized in the sagittal plane to assess lateral extension of arms. In cases where embedment or misplacement of an IUD is suspected, 3D ultrasound is preferred as it provides more detailed diagnostic information on the location and orientation of the IUD arms. Perforation of IUD to an extrauterine location is best identified by X-ray.
How are embedded IUDs removed?
Ring forceps can be used to gently pull on the IUD strings for removal. If the strings are not visualized or the IUD is unable to be removed by applying traction to the strings, the cervix can be dilated and the IUD may be removed with hook or artery forceps under general anesthesia. If all other attempts to remove the IUD have failed, a hysteroscopy may be performed.
Transvaginal pelvic ultrasound images obtained of the uterus demonstrate an absence of IUD arms in the uterine fundus. With scrolling in the craniocaudad direction, there is symmetric posterior acoustic shadowing in the posterolateral aspects of the myometrium compatible with inadvertent placement of IUD arms in the myometrium.
These foci of shadowing can be traced back to the endometrial canal revealing a low lying body of the intrauterine device in the inferior uterus and cervical canal.