What are the next steps for a patient with hyperetonogestrelemia (elevated etonogestrel level) indicating a Nexplanon (etonogestrel implant) is present, but the implant cannot be located through imaging studies?

Management of Non-Palpable Nexplanon with Elevated Etonogestrel Levels

When imaging fails to locate a Nexplanon implant but etonogestrel levels confirm its presence, proceed with high-resolution ultrasound (10-15 MHz linear array transducer) performed by an experienced operator, followed by MRI if ultrasound remains non-diagnostic. 1

Diagnostic Algorithm

Step 1: Confirm Implant Presence

• Elevated serum etonogestrel levels definitively confirm the implant is present in the body, even when non-palpable 1
• This measurement is necessary when imaging cannot visualize the device 1

Step 2: High-Resolution Ultrasound

• Use a 10-15 MHz linear array transducer as the primary imaging modality 1
• The implant can be located just under the skin, under the fascia muscularis, or deep in the muscle 1
• Ultrasound successfully localizes the implant in the great majority of cases 1
• Ensure the examination is performed by an operator experienced in locating non-palpable implants 1

Step 3: Expand Search Area

• Investigate the axillary region first if the implant cannot be found in the expected insertion site 2
• The implant may have migrated proximally along the arm 2

Step 4: MRI if Ultrasound Fails

• Magnetic resonance imaging is the next best choice when ultrasound does not definitively locate the implant 1
• MRI is particularly useful for deeply placed or migrated implants 1

Step 5: Consider Distant Migration (Rare)

• In extremely rare cases, the implant can migrate into the basilic vein and embolize to the pulmonary vasculature 3
• If arm and axillary imaging are negative but etonogestrel levels remain elevated, obtain chest X-ray and CT scan 3
• Nexplanon is radiopaque and detectable on plain radiographs 3, 2

Clinical Coordination

Close coordination between women's health care providers and radiologists is required to minimize removal complications 1

• Communicate the clinical scenario clearly to the radiologist performing the imaging 1
• Ensure the radiologist understands they are searching for a small radiopaque rod that may be in an unexpected location 1

Removal Considerations

Standard Removal

• Once localized, real-time fluoroscopic-guided localization and removal can be accomplished for the radiopaque Nexplanon 2
• Modified techniques may be necessary depending on the implant's depth and location 2

Deep or Migrated Implants

• Endovascular retrieval should be attempted first for vascular migration to spare tissue and avoid surgical incisions 3
• However, encapsulation and adherence to adjacent tissue can complicate endovascular approaches 3
• Surgical removal (including VATS for pulmonary migration) may be necessary if endovascular retrieval fails 3

Common Pitfalls to Avoid

• Do not assume the implant was expelled if it cannot be palpated—elevated etonogestrel levels prove it remains in the body 1
• Do not limit ultrasound examination to the insertion site—scan the entire arm and axillary region 2
• Do not use standard ultrasound equipment—a high-resolution 10-15 MHz linear array transducer is essential 1
• Do not proceed with blind removal attempts—this increases risk of neurovascular injury 1

Incidence Context

• Difficulties with removal, failure to locate, or migration occur in approximately 0.12-1.01 per 1,000 patients with Nexplanon 4
• The newer Nexplanon formulation has reduced the incidence of deep insertions and migration complications compared to the older Implanon 4