Abstract
BACKGROUND: Retroperitoneal ectopic pregnancy (REP) is an extremely rare type of ectopic pregnancy, with a total of less than 32 cases reported in the English literature. Early diagnosis of REP is very difficult and all treatments entail a high risk of life-threatening complications. CASE PRESENTATION: A 29-year-old nulliparous woman presented a history of 50-day amenorrhea and 7-day upper abdominal pain without vaginal spotting. The serum beta-human chorionic gonadotropin (β-hCG) value was 65,004 m-international units per milliliter (mIU/mL), but no intrauterine gestational sac was found via transvaginal sonography (TVS). Then transabdominal ultrasonography (TAS) and abdominal contrast-enhanced computer tomography (CT) identified a retroperitoneal ectopic pregnancy (REP) tightly adjacent to the inferior vena cava and the abdominal aorta. After consultation from a multidisciplinary team, systemic methotrexate (MTX, intramuscular 20 mg daily for 5 consecutive days) combined with ultrasound-guided local potassium chloride solution injection into the gestational sac was scheduled firstly for the patient. However, serum β-hCG continued to increase and the patient experienced worsening abdominal pain. Laparotomy was performed jointly by a gynecologist and a vascular surgeon. During the operation, the gestational sac with fetal bud measuring about 4.5 × 4.0x3.0 cm, tightly adherent to the surface of inferior vena cava and the left side of abdominal aorta, was carefully dissociated out from the surrounding tissues and removed en bloc. Histopathology examination confirmed the diagnosis of REP. The patient recovered uneventfully and her serum β-hCG returned to normal range on the 23(th) postoperative day. CONCLUSIONS: Considering the possibility of REP and combined radiological examinations, such as ultrasonography and CT, are crucial for the early diagnosis of this rare condition. A multidisciplinary team is necessary to treat REP.