An interstitial (cornual) ectopic pregnancy at 10 weeks is found incidentally on MRI in a haemodynamically stable patient. The distinguishing MRI feature of interstitial ectopic compared to intrauterine pregnancy is:
- A Location adjacent to the endometrial stripe with thick myometrial mantle
- B Presence of free fluid around the fundus only
- C Eccentric location with <5 mm myometrial mantle and absence of interstitial line sign ✓
- D Bilateral adnexal ring of fire sign
Explanation
Interstitial ectopic pregnancy implants within the myometrial portion of the fallopian tube as it traverses the uterine wall. On ultrasound and MRI, the defining features are: eccentric position of the gestational sac outside the endometrial cavity, a thin myometrial mantle of <5 mm surrounding the sac, and absence of the 'interstitial line sign' (an echogenic line from the endometrial cavity to the sac edge). Rupture of interstitial ectopics causes catastrophic haemorrhage due to proximity to uterine vasculature. Management may include systemic methotrexate, cornuostomy, or cornual resection.
Reference: Williams Obstetrics, 26th ed.
High-yield for: NEET PGINI-CETNExTFMGEUSMLEPLABMRCP
Written and medically reviewed by the StethoPrep medical team.