A 23-year old female patient presented to the emergency department with a sensation that her intrauterine device (IUD) was out of place.  The patient had the device placed 2 weeks ago.  She was checking at home, thought she felt a piece of plastic, and presented to the emergency department.  She denied any vaginal bleeding, pelvic pain, or vaginal discharge.  On pelvic exam only the strings were visible with no IUD plastic seen at the cervical os.

A bedside ultrasound was performed:

A transvaginal probe was used.  The first clip shows the uterus in transverse (“short-axis”) view.  The endometrial stripe is seen, with no obvious IUD visualized.  Towards the end of the clip a linear hyperechoic object is seen in the lower uterine segment and within the cervix.  This is the long shaft of the IUD which is inferiorly displaced within the cervix.  The patient was told her IUD was malpositioned.  She had a follow up appointment with her primary care doctor the next week for a recheck.

Intrauterine devices are becoming a more popular form of reversible contraception,and are becoming more common in the United States.  One out of twenty (5%) contracepting women use IUDs today, a marked increase from less than 1% in 1995.  Most IUDs are placed blindly, however ultrasound is commonly used to evaluate for proper IUD position and assess for other complications.  

One retrospective study of patients with IUDs receiving ultrasound for any indication showed about 11% were malpositioned.  Malposition is most commonly associated with symptoms of pain and bleeding, but patients may also be asymptomatic.   A malpositioned IUD is defined along a spectrum.  Expulsion is passage of the device either partially or completely through the cervical os.  Displacement is rotation or inferior positioning in the lower uterine segment or cervix.  Embedment is when the device (either stem or side-arm) embeds within the myometrium of the uterus.  Perforation occurs when the device penetrates through the myometrium and the serosa.  The risk of expulsion is greatest within the first year of placement, and greater in immediate postpartum placement.  Embedment and perforation are much more rare, and seen at a rate of 1-2 per 1,000.  They are more common when placed by inexperienced operators and in the early postpartum period.  

Displacement used to be defined as a distance of more than 3 mm between the uterine fundus and the IUD.  However, more recent studies seem to suggest the majority of inferiorly displaced IUDs will move to a the fundal position within a few months.  Displaced IUDs  have been associated with less efficacy.  How much displacement is needed to decrease efficacy is unknown.  Some studies have shown that displaced copper IUDs have increased risk of pregnancy compared to displaced hormone-releasing IUDs.  Any decreased efficacy of a displaced IUD also needs to be weighed against the risk of pregnancy if the IUD is removed without an alternative form of contraception in place.

The stem of IUDs is easily visible on transvaginal ultrasound (sometimes transabdominal as well) and appear as a hyperechoic linear line with posterior acoustic shadowing.  The side-arms that form the “T” are echogenic with copper devices (the Paraguard) but less visible on the levonorgestrel-releasing device (the Mirena).  Using two-dimensional ultrasonography the IUD can be measured in two planes.  Three-dimensional (3D) reconstructions are a newer imaging technique that creates a coronal view of the uterus.  This allows better assessment of side-arms, and is more sensitive than 2D imaging for side-arm embedment in the myometrium.  However, not all radiology departments will routinely perform the 3D coronal view of the uterus to assess proper IUD position.

Ultrasound is the best initial imaging test to assess for IUD position because it is low-cost and low-radiation.  If the IUD is not visible on ultrasound or exam (and the patient doesn’t remember the device being expelled) then an abdominal radiograph can be obtained.  All IUDs are radioopaque.  The IUD should sit low in the pelvis along the midline, although the exact position may vary depending on the position of the uterus.  CT or MRI can also be performed if there is a higher suspicion for perforation, abscess formation, or other complications.

Pearls

Perform ultrasound as the first imaging test if you have concern for a malpositioned intrauterine device

Malpositioned IUDs occur along a spectrum, with displacement and expulsion more common than the more severe complications of embedment and perforation.  

Any imaging concerning for IUD malpositioning should be communicated with the patient and followed up with the provider who originally placed the device.  

Mark Robidoux, Emergency Ultrasound Fellow