Pre-rupture diagnosis and conservative surgery for ovarian ectopic pregnancy hidden by an endometrioma, guided by the transvaginal ultrasound “sliding organ sign”: a case report and literature review

BACKGROUND: Ovarian ectopic pregnancy (OEP) is a rare and life-threatening condition that is typically diagnosed post-rupture. Its diagnosis and management become more complex when it is concurrent with ovarian endometrioma, as the latter may mask the clinical and radiological features of OEP. CASE PRESENTATION: We report the case of a 28-year-old woman (gravida 2, para 1) who presented with 44 days of amenorrhoea and lower abdominal pain. Transvaginal ultrasound (TVS) revealed an empty uterus, a complex right adnexal mass containing a yolk sac (with synchronous movement with the ovary and a negative "sliding organ sign", raising a strong suspicion of ovarian ectopic pregnancy), and a separate "ground-glass" cystic lesion (consistent with an endometrioma). Corpus luteum blood flow signals were detected in the left ovary. The patient's preoperative haemoglobin concentration was 128 g/L. Diagnostic laparoscopy confirmed a right ovarian pregnancy co-existing with an ipsilateral endometrioma. Both lesions were excised laparoscopically while preserving the ovary. Haemostasis was achieved by primary suturing supplemented with minimal bipolar coagulation to preserve ovarian function. The patient recovered well; her postoperative haemoglobin concentration was 122 g/L, and her menses resumed at 6 weeks post-operatively, which confirmed preserved ovarian function. CONCLUSIONS: This case reaffirms a fundamental clinical principle: any reproductive-age woman with a positive pregnancy test, an empty uterus, and an adnexal mass should be presumed to have an ectopic pregnancy, prompting immediate surgical evaluation. In our patient, this principle alone mandated surgery. The transvaginal ultrasound findings (a yolk sac and a negative "sliding organ sign") did not change the need for surgery, but they provided critical preoperative localization of the gestational sac to the ovary. This allowed us to anticipate an ovarian pregnancy, obtain specific consent for ovary-conserving surgery, and plan a suture-dominant haemostatic strategy. To our knowledge, this is the first reported case of pre-rupture diagnosis of an ovarian ectopic pregnancy masked by an endometrioma using these sonographic signs. Clinicians must prioritize the clinical triad; when available, meticulous ultrasound adds precision for fertility preservation.