Serum Etonogestrel Level Testing for Non-Palpable Nexplanon
If a Nexplanon implant cannot be located on X-ray, measure serum etonogestrel levels to confirm the presence of the implant.
Diagnostic Approach for Non-Palpable Implants
When a Nexplanon implant cannot be palpated or visualized, the following algorithmic approach should be used:
First-Line Imaging
- X-ray imaging should be the initial step since Nexplanon contains 15 mg of barium sulfate making it radiopaque and visible on X-ray 1, 2
- If the implant is not visible in the arm on X-ray, obtain a chest X-ray to rule out migration to the pulmonary vasculature, as rare cases of embolization through the basilic vein to pulmonary arteries have been documented 3
Laboratory Confirmation
- Serum etonogestrel level measurement is the blood test used to confirm presence of the implant when imaging fails to localize it
- Detectable etonogestrel levels indicate the implant is present somewhere in the body
- Undetectable levels suggest the implant was never inserted, has been expelled, or has reached the end of its effective lifespan (>3 years) 4
Additional Imaging if Needed
- Ultrasound examination can be considered if X-ray fails to localize the implant 5
- CT scanning may be necessary if migration is suspected, particularly to identify implants that have embolized to the pulmonary vasculature 3
Clinical Context
The etonogestrel implant is a single 4 cm rod containing 68 mg of etonogestrel that provides contraception for 3 years 5, 1. While highly effective with less than 1% failure rate 5, non-palpable implants require systematic evaluation to ensure proper placement and function.
Important Caveats
- All providers must be trained in Nexplanon insertion and removal procedures before performing these procedures 4
- Migration to pulmonary vasculature, while exceedingly rare, can occur through injured basilic vein walls and may require endovascular retrieval or surgical removal if the patient desires fertility restoration 3
- The implant must be removed by the end of the third year, after which fertility returns rapidly 4