A challenging diagnosis of interstitial ectopic pregnancy confounded by sonographic signs of adenomyosis: a case report

Interstitial ectopic pregnancies account for 1%-3% of ectopic pregnancies and carry a high risk of morbidity due to delayed diagnosis and potential catastrophic haemorrhage. Sonographic identification is challenging and may be further confounded by distorted pelvic anatomy, including adenomyosis, which can present with myometrial cysts or sub-endometrial microcysts that mimic a gestational sac. We describe a 36-year-old woman presenting with early-pregnancy bleeding whose initial ultrasounds suggested a possible intrauterine pregnancy due to adenomyosis-related cystic changes. Serial serum human chorionic gonadotropin (hCG) levels rose sub-optimally, and specialist ultrasound ultimately confirmed a right interstitial ectopic pregnancy. She underwent successful laparoscopic uterine wedge resection and bilateral salpingectomy with the use of intramyometrial vasopressin and tranexamic acid to minimize blood loss. This case highlights the importance of vigilance in pregnancies of unknown location, particularly when adenomyosis distorts sonographic anatomy, and demonstrates the role of minimally invasive techniques and haemostatic adjuncts in reducing morbidity.