Chapter 3. IUD Types and Sonographic Characteristics

Introduction

According to the most recent data, intrauterine device (IUD) usage in the United States has increased from approximately 2% in 2002 to about 11.6% among women aged 15–49 who use contraception. The highest prevalence is observed in the 25–34 age group. Usage rates have also risen among adolescents, reaching up to 6%. Globally, the rate of IUD use stands at 14%.^1,2

While complications with IUDs are uncommon given the number of woman-years of usage, certain challenges still exist. As many as 20% of IUD insertions are classified as “difficult.” Many of these issues can be identified using point-of-care ultrasound. Some complications can become serious or burdensome, not to mention increasing the risk of failed contraception.³

This chapter and chapter 4 will explore the types of IUDs, as well as the common problems encountered by clinicians. It will explain how POCUS is used to help with prevention, patient counseling, and guidelines for management

Types of IUDs

Currently in the United States there are two IUD types available. One type consists of a T-shaped polyethyline device and the other type of IUD is the LNG-IUS (“levonorgestrel intrauterine system”) device. The copper device contains no hormone but instead has a tiny copper wire around the stem and both arms. The copper wire releases copper ions that create a sterile but inflammatory environment for the sperm. Copper also thickens the cervical mucus making it less favorable for sperm and for implantation.

The levonorgestrel devices are made of a polydimethylsiloxane (silicone) elastomer, covered by a drug rate-controlling membrane. They vary in size and amounts of levonorgestrel release, allowing for some customization for uterine size, endometrial effect, and time length of effectiveness. Levonorgestrel thins the uterine lining, making it less favorable for implantation, as well as thickening cervical mucus, reducing sperm motility. Because levonorgestrel thins the uterine lining, it has a secondary benefit of reducing blood flow during menses. Desire for oligomenorrhea and amenorrhea are usually an important consideration for women with a history of heavy menstrual bleeding.

Each type has a 99% efficacy rate. The primary difference is in their effects on the endometrium and their predicted efficacy duration.

IUDs have been used for hundreds of years, but in the U.S IUD’s were removed from the market in the mid 1980’s due to concerns for increased risk of pelvic inflammatory disease and subsequent infertility, However, they were re-introduced back in the late1980s, having been redesigned to minimize this risk.

IUD characteristics by Type

The following figures show the size and configuration of the types of IUDs available. Figure 1 is of the copper T device. Figures 2 and 3 (below) show the LNG-IUS devices available, with their respective descriptions.

Figure 1. The copper-T IUD.

32 x 36 mm White threads, duration 10 years

Figure 2. 52-mg LNG-IUS

32 x 32 mm

White threads – 8 yrs duration

Blue threads - 5 yr duration

Figure 3. 19.5 and 13.5 mg LNG-IUS

28 x 30 mm, Silver ring

Blue threads – 5 years

Silver threads – 3 years

Practitioners who provide IUDs for their patients should have an understanding of the types of IUDs and their unique characteristics for tailoring to an individual woman’s clinical needs. We will first describe the size differences of the various IUDs since there is a case to be made for trying to fit the right IUD with the right size of uterine cavity.⁴

Indications for IUD use

Contraception

Women’s health providers are presumably knowledgeable about contraceptive benefits of IUDs. The purpose of this chapter is to help providers to use ultrasound in identifying IUDs and troubleshooting difficulties in insertion and malposition.

Emergency Contraception

Another use for the IUD is for use as emergency contraception (EC). The copper IUDs were the first IUD to be considered effective for emergency contraception due to its high efficacy rate (99.9% efficacy if inserted within 7 days of unprotected sex).⁵

However, LNG-IUS devices have since become also widely used. The 52 mg LNG-IUS can be used as emergency contraceptive if inserted within 5 days of unprotected intercourse. Even though the LNGIUS is not FDA approved for emergency contraception it is still used due to its high effectiveness rate comparable to the copper IUD. If a woman does not desire to have a copper IUD long term, the LNG-IUS is a good alternative for use as both EC and for extended use.⁶ Many women wish to continue using the IUD beyond the emergency contraception benefit for managing dysmenorrhea and heavy menstrual bleeding.⁵

Noncontraceptive uses of LNG-IUS

The indications for using LNG-IUS for noncontraceptive benefits include:

--dysmenorrhea, heavy menstrual bleeding (HMB), fibroids, postmenopausal (for estrogen opposition)

--history of anemia due to blood clotting disorders (such as Von Willebrands, eg) or perhaps those who take blood thinners

Levonorgestrel in the LNG-IUS affects the endometrium by thinning it, reducing menstrual volume. Menstrual volume scores of study cohort after 1 month, 2 months, and 3 months following treatment were remarkably lower than those before treatment.

Patients’ menstrual flow can be controlled, and anemia can be corrected; thus, patients improve their quality of life and health status.

The 52 mg LNG-IUS is very effective in the treatment of perimenopausal abnormal uterine bleeding (once pathology is ruled out). It allows peri and postmenopausal women (who still have a uterus) to be able to take oral estrogen without having to oppose it with oral/systemic progestins.

IUD Identification with Ultrasound

This next section will review how to identify the IUD and determine its correct position. Each type of IUD has a unique sonographic configuration and those will be demonstrated. Ultrasonography is the most common initial method of evaluation due to its cost-effectiveness, lack of ionizing radiation used in X-ray, and greater detail of soft tissue in pelvic anatomy.

The following images show the unique sonographic characteristics of the types of IUD to determine which IUD is being used.

The copper IUD, when imaged shows a single rod or stem that is highly echogenic when viewed in the long or sagittal plane. (Figure 4). The central shaft (stem) is uniformly echogenic due to the copper coils around it.⁴ When the transducer is rotated transversely at the uterine fundus, the arms should be viewed as extended laterally toward the cornua in a symmetrical fashion. The arms of the copper IUD are also fully echogenic due to the presence of the copper coils.

Figure 4. Copper IUD shown in sagittal view on the left and coronal view on the right image. Note: POCUS imaging does not typically allow for 3D imaging, but this image is presented to give an idea of the general placement of the IUD.

Figure 4. Copper-T device: sonographic appearance

Both types of IUDs create a shadow behind the stem due to the density of the stem reflecting the sound back to the transducer, reducing its travel deeper into the body.

LNG-IUS

Below, Figure 5 is of the 52-mg LNG-IUS. This device shows a trilaminar echo because it has a hollow shaft/stem containing the levonorgestrel. The stem’s plastic sleeve creates an acoustic shadowing and has a ‘laminated’ appearance with parallel lines.⁷

This makes for a “double” echogenic line since the ultrasound picks up both sides of the stem.

The 52mg device also has barium sulfate in the arms as well as an echogenic distal tip.⁷

The arms of the levonorgestrel-releasing IUD are only echogenic at the proximal and distal ends, in the transverse view, but the central transverse view of the stem is recognizable by the shadow it casts, even if the stem itself is not seen.⁸

Figure 5. 52 mg LNG-IUS device sonographic appearance

The 19.5 mg and 13.5 mg IUDs have a similar configuration, but these IUDs have a silver ring 3-4 mm below the crossbar where the arms extend. This silver ring is highly echogenic and gives a characteristic white “dot” shown by the yellow arrow in Figure 6 below.⁷

Figure 6. Image of a 19.5mg LNG-IUS showing the echogenic ring at the top of the IUD stem.

Correct IUD Placement

The correctly positioned IUD is located in the uterine cavity near the fundus (Figure 7). The stem should extend toward the cervix and the two arms should be fully unfolded during insertion, reaching laterally toward the uterine cornua. The stem is easily identified on standard two-dimensional (2D) transvaginal ultrasonography (TVUS) as a linear echogenic structure. If no TVUS is available, a transabdominal ultrasound can usually be sufficient to determine the IUD position, if the woman has a full bladder and her uterus is anteverted.

Three-dimensional (3D) imaging is increasingly being used, particularly for the coronal view, which allows for a more careful evaluation of the arm positioning. ⁸ As helpful as 3D imaging is for precise IUD localization, most providers of POCUS do not have that function on their machines. So it is important to carefully evaluate the IUD location and position in both sagittal and transverse views to see if referral for 3D imaging is warranted.

Figure 7. Identification of IUD general principles

Figure 8. Appearance of the IUD in sagittal view (left) and transverse view (right)

Protocol for Ultrasound of the IUD

Ultrasound imaging of intrauterine devices (IUDs) should include assessment of body,arms, and endometrial cavity in relationship to each other, both abdominally and transvaginally.⁹

The correctly positioned IUD is located in the uterine cavity near the fundus (Fig. 2). The stem should extend toward the cervix and the two arms should be fully unfolded during insertion, reaching laterally toward the uterine cornua.⁸

While 2D imaging can confirm intrauterine positioning, it can be more difficult to visualize the arms of the LNG-IUS devices than with viewing the copper IUD. It is possible for an IUD to appear correctly placed in the sagittal view, but be either embedded or rotated in the transverse view.¹⁰

Most non-fundal IUDs are located in the lower uterine segment or cervix, which can be typically identified with ultrasound. Some malpositioned IUDs appear to be embedded in the myometrium on more detailed imaging.¹¹

Chapter 4 of this course will describe imaging of malpositioned IUDs in greater detail.

Below are images depicting how to view the uterus and IUD in both the sagittal and transverse views. Figure 9 shows the brighter echogenicity of the IUD stem, and behind it the characteristic shadow. It also shows the bright lines of the strings, which are also echogenic.

It is important to distinguish between identifying the IUD itself and the strings since both are echogenic. The strings will be thinner lines. If the only echogenic feature you can see is in the cervix, look further into the uterus to find the IUD so that you do not mistakenly think the strings are the IUD stem. Figure 9 below shows imaging of a uterus in the sagittal plane without a clear view of the IUD itself. The strings are seen, however, in the cervix. When the transducer is rotated at the fundus to get a transverse view, the arms are seen correctly extending toward each cornua, so the IUD is in the correct position.

Figure 9. Image showing IUD strings (left) and arms extended correctly in transverse (right lower image)

Figure 10. Sagittal view of the correctly placed IUD demonstrating the stem and the strings (which are also echogenic)

When viewing the IUD in the transverse plane at the fundus, look for two things: 1) the central transverse “dot” with shadow from the cross-sectional view of the stem and 2) the symmetrically extended arms near the fundus (See Figure 10 below)

When viewing IUDs, keep in mind the principles learned in the previous GYN lecture: the retroverted or retroflexed uterine fundus leans toward the right of the screen, rather than the left (with an anteverted uterus). So the fundus is at the opposite side of the screen from an image of an anteverted or anteflexed uterus.

Figure 11. Image of a correctly placed IUD in a RETROVERTED uterus.

Figure 12. Image of an ANTEVERTED uterus with a copper IUD.

Figure 13. Transverse view of the IUD arms extended at the uterine fundus

Figure 14. Transverse views of imaging the IUD. The red dotted line indicates the level of the transducer transecting the uterus.

Figure 15. Transverse view of the IUD stem casting a shadow due to its density

Figure 16. Image of the echogenic distal ends of a LNG-IUS device

Most of the images shown in this chapter are of transvaginal scans since the images are clearer to help you see how IUDs should appear. However, it is possible to see IUDs fairly well even with transabdominal sonography, provided that the patient’s body habitus not a deterrent.

Figure 17. Transabdominal sagittal view of the IUD in the uterus.

Figure 18. Transabdominal sagittal view of LNG IUS.

Figure 19. Transabdominal view of IUD. Left image: sagittal, right image: transverse

Figure 20. Transabdominal view of an acutely anteflexed uterus with difficulty seeing the IUD in the sagittal view, but arms are seen in the transverse plane.

Indications for performing POCUS for IUD management

There are 4 primary reasons to perform imaging in the management of IUD complications:¹²

• Difficult Insertion

• Patient symptoms – often related to malposition

• Strings not visible by palpation or on exam

• Expulsion

The remainder of this chapter will focus on the aspects of difficult IUD insertion and use of ultrasound to help with identifying the causes.

DIFFICULT INSERTION

The most common reasons for difficult insertion include:

1. Severe insertional pain

2. Cervical obstruction

3. Fibroids

4. Polyps (cervical or uterine)

5. Mullerian defects

Pre-insertion uterine measurement

Pre-insertion Uterine Sounding

Sounding the uterus prior to IUD placement appears to have originated at a time when it was being used for other procedures. IUDs have changed, as have certain protocols for IUD placement, but there is no clear evidence for supporting this practice according to Goldstuck.¹⁰Insertion of IUDs is considered a minimally invasive procedure, and eliminating uterine sounding can minimize pain with insertion. There can also be cervical trauma with the insertion of the sound itself. Not sounding allows for a simpler insertion procedure, reduction of pain and possibly decreased introduction of bacteria into the endometrial cavity.¹⁰ It may be considered unnecessary if the insertion is a replacement procedure and there were no problems with the prior IUD. If sounding is the given protocol for your institution, you should follow best practices identified there. Just be aware of the latest suggestions to forego sounding in some cases.

Figure 21. Uterine sounding guidelines by IUD type¹³

Is there a case for pre-insertion uterine measurement with ultrasound ?

Would assessing endometrial dimensions prevent inappropriate IUD size selection or help detect characteristics causing impeded insertion or increased risk of expulsion?

Cintesun ¹⁵ conducted a study to evaluate the relationship between displacement and IUD positioning in the uterus, looking at uterine dimensions as measured with transvaginal ultrasonography (study number 384). Women with endometrial width less than 41.5 mm were more likely to have displacement. They also concluded that the distance of the top of the IUD and the upper endometrium, as well as the cavity width, are important risk factors for displacement of the copper IUD. The expulsion rate of the device was 6% in the first year after insertion.

Despite what one would think, the longer the uterine cavity, the higher the expulsion rate. Studies determined increased risk with a uterine cavity length of 37-45 mm.

Shorter uterine length measured by ultrasound seems to be a predictor for HMB/ menorrhagia in patients with an IUD, making a possible case for pre-insertion ultrasound, especially in nulliparous women or those who have had prior IUD expulsion. Since shorter cavity length is a predictor of menorrhagia in patients with a copper-T, this may be a cause of the increased expulsion rate with this device. Patients experiencing both HMB and pelvic cramping with an IUD are more susceptible to expulsion.^14,15,16

This could alter decision-making related to the decision of IUD type if she is presented with this information. Knowing that her shorter uterine cavity length could increase her risk of HMB with a copper IUD, she may elect to choose a LNG-IUS.

Figure 22. Illustration of typical intrauterine dimensions of nulliparous women compared to multiparous women.

Figure 23. Diagram comparing dimensions of IUD types.

Despite the potential benefits for uterine ultrasound measurement pre-insertion, it would be a deterrent to providing services in low-resource areas, as well as adding cost and time by adding another procedure. Uterine sounding is then a viable alternative.¹⁴

Indications for Pre-insertion Ultrasound

Excessive pain or obstruction during insertion attempt

Common practices have been suggested for anticipation of difficult IUD insertion. The use of misoprostel to “soften” the cervix has been widely used. However, evidence suggests that misoprostel not only fails to reduce patient pain or improve insertion success, it increases insertion and post-insertion pain, reducing patient satisfaction. It also may increase abdominal pain, cramping and diarrhea.⁵

Despite the evidence cited, it may still be an option to use misoprostol for women with failed insertion attempts due to cervical rigidity or stricture. The typical doses of misoprostol are: 400 μg vaginal misoprostol (200 μg administered 10 hours before and 200 μg administered 4 hours before).¹²

Pain management is an important part of IUD insertion technique. Evidence suggests that topical lidocaine applied to the cervix (2% gel 5-15 min prior to insertion) might reduce patient pain associated with tenaculum placement. ACOG also reports that paracervical block using lidocaine is often helpful for managing insertion pain. It was noted, though, that use of topical lidocaine did not reduce adverse events or need for additional measures such as cervical dilation.¹²

Some providers use in-office nitrous oxide for pain management during insertion, especially for anxious patients.

Sonographic identification of cervical or uterine obstruction

When inserting an IUD it is possible to encounter unanticipated obstructions. These can be related to a variety of causes. At times a provider may continue to push forward, hoping to move past the obstruction, but without success. It is much better to stop and evaluate the cause before re-attempting due to increased risk of cervical inflammation and bleeding, as well as increasing patient pain, all of which can make insertion more difficult..

The most common reasons for encountering obstruction during IUD insertion are:

1. Uterine flexion or abnormal position

2. Cervical obstruction

3. Fibroids

4. Polyps

5. Mullerian defects

Uterine flexion or abnormal position

One typical protocol for pre-insertion of an IUD has been performing a bimanual exam to determine uterine direction and flexion. This could prevent a number of insertion problems.

One certain advantage of uterine sounding is to detect an abnormal cervical or uterine position before attempting the IUD insertion and potentially having to waste a device that will not insert.

Some authors state that IUD perforation is more likely to occur during insertion. This may be the case in some circumstances, such as the illustrations in Figure 21. This type of perforation presumes an exceptional amount of force applied, which is not recommended especially if there is obstruction.

Figure 24. Acutely angled uterine positions demonstrating potential for perforation during IUD insertion.

Figure 25. Image of a uterus that is angled slightly posterior, but the uterus is bent backwards toward retroflexion.

Figure 26. Image of a uterus that is acutely retroflexed. The angle between the cervix and endometrium is almost 90 degrees, indicating it could be difficult to insert the IUD around the bend.

Figure 27. Is an illustration of a uterus that is midposition, but that the angle of the cervix is such that a straight insertion of an IUD would push up against the posterior wall of the uterus and prevent insertion to the endometrium.

Figure 27. Illustration of angled cervix

Cervical Obstruction

Cervical Stenosis

The portion of the uterus between the cervix and the uterine body is known as the isthmus. This is the narrowest portion of the uterus, and can be the site of various pathologies.¹⁷

Scarring of the isthmus can be related to prior surgical procedures (such as cerclage, D&C, or even unrepaired cervical lacerations associated with childbirth) Isthmic uterine lesions may be classified as an ithsmocele . An IUD can be obstructed by this tissue. During insertion, the provider may consider the uterus to be just “short” when sounding, when in reality the cervix has not been penetrated. This could cause the IUD to be placed within the cervical tissue rather than in the endometrium.

Figure 28. Drawing of cervical stenosis

Figure 29. Image of cervical scarring or isthmocele

jhnu

Figure 30. Image of cervical stricture possibly from scarring (prior uterine surgery such as C/Section or D&C)

Figure 31 is an image of a very uncommon condition known as atriovenous malformation. This causes tissue thickening that can obstruct the endometrium. AVM is a tangle of abnormal blood vessels where arteries are connected to veins. In addition to stricture, the biggest risk with IUD insertion is disruption of the AV network causing severe hemorrhage. It can manifest as persistent uterine bleeding on her gyn visit. It would not be unusual for a provider to consider a LNG-IUS if a woman presents with these symptoms, and be unaware that this condition exists without an ultrasound.

Figure 31. AVM (uterine atriovenous malformation) – possibly due to surgery or trauma

When providers encounter difficulty traversing the cervical canal, it can be due to a turn in the canal that is opposite of the angle of insertion. Sometimes moving the sound in different directions can help identify which direction the cervix is angling. The use of Hegar dilators is very helpful in these situations. Since these dilators are rigid but curved with a rounded end, they are often less traumatic to insert than the sharp uterine sounds. The curve can be rotated to find the curvature of the cervix and identify the correct angle to insert the IUD.

Figure 32. Hegar dilators

Fibroids

Uterine fibroids are one of the most common uterine findings. The incidence is up to 70% of Caucasian women by the age of 50, and up to 80% of black women. They are typically benign growths of fibrous tissue resembling keloids and can occur in a number of locations on or in the uterus. Figure 30 is a diagram illustrating the most common locations of uterine fibroids, sometimes called leiomyoma or myomas. As one can surmise by looking at the illustration, the fibroids that could cause the most concern with IUD insertion are those near the cervix and those within the uterine cavity (submucosal).

The presence of fibroids is not a contraindication for IUD insertion unless they are obstructing the cervix or endometrium. This would have to be assessed with ultrasound prior to insertion. Since LNG-IUS devices are indicated for heavy menstrual bleeding, they are also recommended for women with fibroids that cause it, provided that the device can be placed appropriately in the uterine cavity. The presence of fibroids does increase the risk of expulsion and malposition, as will be discussed in Chapter 4.

Figure 33. Illustration of uterine fibroids

Figure 34. Image of a submucosal uterine fibroid occupying the entire endometrium, making it virtually impossible to insert an IUD

Polyps

Uterine and cervical polyps are typically benign growths of tissue arising from mucus membranes, such as in the endometrium or cervical canal. They are typically soft, but can cause abnormal bleeding. An IUD may be placed penetrating through the cervical polyp, but if it causes the polyp to bleed, then it may require removal of the IUD to determine the cause of bleeding. Polypectomy usually resolves the problem and can either be removed in the office or with hysteroscopy depending on the location. Polyps differ from fibroids, but small submucosal fibroids can appear like polyps. As a POCUS provider, you would not be required to discriminate this – you simply need to recognize the presence of a mass.

Figure 35. Image of cervical polyps

Mullerian defects

Mullerian anomalies occur in roughly 0.5 % to 6.7% of women. These can present as mild abnormalities, to anomalies preventing either conception or a contraindication to the use of an IUD. Figure 33 is an illustration of the variety of Mullerian defects that can occur. As is obvious in the illustration, there are problems encountered with either insertion or correct placement of an IUD in most of these situations.

Figure 36. Illustration of common Mullerian abnormalities

Figure 37. Image of a bicornuate uterus: left is the sagittal view and right is the transverse of the upper uterus showing 2 separate endometria (one in each horn)

Figure 38. Image of a transverse view of the upper part of the uterus showing the endometria in 2 separate horns.

As Figure 39 (below) demonstrates, an IUD could easily be placed inside of one horn and leave the other horn vulnerable to pregnancy implantation, especially if the IUD is a copper T.

Figure 39. Illustration of an IUD placed in one horn of the bicornuate uterus

Ultrasound Guided IUD Placement

Ultrasound guidance for IUD placement may be a recommended procedure for those women who have had a prior difficult or failed insertion, or in those identified as having an abnormally configured uterus. It is also helpful in women who have demonstrated uterine abnormalities, such as fibroids. It can be useful to observe the IUD as it navigates to the correct place in the upper endometrium.⁹

YOU MAY NOW TAKE THE QUIZ AND MOVE TO THE NEXT CHAPTER. YOU WILL NOT BE ABLE TO OPEN THE NEXT CHAPTER UNTIL YOU COMPLETE AND PASS THE QUIZ. YOU WILL HAVE AS MANY TRIES AS YOU NEED TO GET ALL THE ANSWERS CORRECT!

Links to Supplemental Materials for POCUS and IUD Evaluation

Iud insertion using ultrasound

https://www.tiktok.com/@drpkobgyn/video/7436184863687855390

Using POCUS to identify IUD placement

https://youtu.be/R0hnHGPMbgw?si=ZUPH4ADmnP869Vwr

Link to article reference: Stalnaker and Kauniz, “How to identify and localize IUDs on ultrasound”

https://blogs.the-hospitalist.org/content/how-identify-and-localize-iuds-ultrasound

.