Diagnostic Challenges in Ectopic Pregnancy: Identifying Pseudo Sacs in Suspected Heterotopic Cases

BACKGROUND A pseudo-gestational sac (pseudo sac), or intracavitary fluid, occurs in up to 10% of ectopic tubal pregnancies and can mimic an intrauterine gestational sac, posing a diagnostic challenge. Distinguishing a pseudo sac from a true gestational sac or an ovarian cyst is critical to avoid misdiagnosis. This report describes the case of a 28-year-old woman presenting at 6 weeks of pregnancy with hydrosalpinx, hemosalpinx, and a pseudo sac due to tubal ectopic pregnancy. CASE REPORT A 28-year-old woman, G3P1A1 at 6 weeks of pregnancy, presented with right lower quadrant abdominal pain lasting 4 days and vaginal bleeding that began 10 h before admission. Physical examination revealed cervical motion tenderness and bulging of the Douglas pouch. Ultrasonography showed a suspected heterotopic pregnancy, with a gestational sac in the right adnexa measuring 1.0×7.4×1.9 cm and a "ring of fire" sign, alongside free fluid in the Douglas and Morrison pouches. Intraoperative findings confirmed a ruptured ectopic pregnancy in the interstitial portion of the fallopian tube, with approximately 400 cc of blood clots. Bilateral salpingectomy was performed, owing to the ruptured ectopic pregnancy and contralateral hydrosalpinx. Histopathological analysis confirmed the intrauterine finding as a pseudo sac with no conception tissue. CONCLUSIONS This report highlights the importance of distinguishing between true intrauterine pregnancy and a pseudo-gestational sac, to avoid unnecessary interventions. It emphasizes the role of early and precise transvaginal ultrasonography combined with histopathological confirmation in diagnosing ectopic pregnancies, particularly in cases mimicking heterotopic pregnancy.