Multidisciplinary treatment of retroperitoneal ectopic pregnancy: a case report and literature review

Ectopic pregnancy is a major cause of maternal mortality and morbidity encountered in the first trimester [1]. Nearly all ectopic pregnancies (95%) are implanted in the fallopian tube, whereas only merely 1% of ectopic pregnancies are implanted in the abdominal cavity [2]. Retroperitoneal ectopic pregnancy (REP), in which the gestational sac is implanted in the retroperitoneal cavity of the pelvis and abdomen, refers to an extremely rare type of abdominal ectopic pregnancy [3]. Once a retroperitoneal gestational sac ruptures, it can cause a catastrophic hemorrhage, especially for those located close to large blood vessels [3‐5]. Here we report a case of REP implanted on the surface of the inferior vena cava, as well as the abdominal aorta, which was successfully treated in a multidisciplinary team. In order to provide reference for clinical practice in the diagnosis and treatment of REP, we also conducted a review on all of the reported cases in English literature.

A 29-year-old pregnant woman, gravida 1, para 0, one previous artificial abortion, with regular menstrual cycle, was admitted via the emergency department on December 27 2021 with a history of 50-day amenorrhea and 7-day moderate to intermittent upper abdominal pain. She had no injury history or history of previous pelvic inflammatory diseases or gynecological surgery. Her vital signs were within normal range. General physical examination revealed nothing remarkable. Gynecological examination found no vaginal spotting, and the uterine cervix was smooth without tenderness upon palpation and movement; the uterine body was soft and enlarged equivalent to the size of 50-day-gestation; the right adnexa was slightly thickened without tenderness; and the left adnexa was unremarkable. The serum beta-human chorionic gonadotropin (β-hCG) value was 65,004 m-international units per milliliter (mIU/mL) on admission. Color transvaginal ultrasonography (TVS) of the pelvis demonstrated no intrauterine gestational sac but thicken endometrium of 1.7 centimeter (cm) (Fig. 1a), a right adnexal well-bounded, medially echoic mass approximately 2.3 × 2.0 × 2.0 cm in size with signs of blood supply; no fluid collection in the pouch of Douglas. Because the results of TVS were not parallel with the clinical characteristics and serum β-hCG level, a full transabdominal ultrasonography (TAS) was applied to extend the scan scope. TAS scan revealed a heterogeneous mass approximately 3.8 × 3.1 × 2.3 cm in size, which consisted of a gestational sac with an 4 mm embryo bud with positive cardiac pulsation (Fig. 1b). The pregnancy mass was tightly adjacent to the inferior vena cava and the abdominal aorta. We furtherly completed an abdominal contrast-enhanced computer tomography (CT), which showed the gestational sac with the embryo in the retroperitoneal space and detailed its tight link with the great vessels alongside (Fig. 1c). Highly suspected of rare REP and lack of experience in the diagnosis and treatment of this disease, a multidisciplinary consultation composed of a gynecologist, a vascular surgeon, a radiologist and an interventional physician was scheduled. For fear of vascular injury and unmanageable intraoperative bleeding potentially associated with excising this mass, the patients decided to administer systemic methotrexate (MTX) combined with local potassium chloride solution injection guided by ultrasonography. Daily 20-miligram(mg) intramuscular MTX for 5 consecutive days was initiated on December 28, 2021. And on the same day, ultrasound-guided paracentesis and local potassium chloride (KCl) injection into the embryo bud was operated successfully (Fig. 1d). On December 30 2021, serum β-hCG elevated to 79,382 mIU/ml, but a repeat TAS showed that though the size of REP mass didn’t change, the fetal heart beat was gone. The patient remained stable with close observation in the hospital. Then the medication therapy was continued. However, on December 31 2021, the patient reported worsening abdominal pain and her serum β-hCG level continued to increase (81,447 mIU/ml). Consequently, the patient agreed to undertake an exploratory laparotomy despite stable vital signs and no drop in hemoglobin level (Hb 118 g/L). This was accomplished through a midline incision about 20 cm in length under general anesthesia. While exploring the pelvic cavity, we found a slightly enlarged and soft uterus with bilateral intact fallopian tubes. The left ovary was completely normal while a corpus luteum about 2.0 × 2.0 cm in size was found in the right ovary without active bleeding. No evidence of lesion and pelvic adhesion was found. No fluid collected in the abdominopelvic cavity. Then an abdominal vascular surgeon joined the operation. Further exploration of the upper abdomen revealed a retroperitoneal mass measuring 4.5 × 4.0 × 3.0 cm, inferior the transverse mesentery and directly attached tightly to the surface of inferior vena cava and the left side of abdominal aorta, with a small amount of local retroperitoneal hemorrhage. The retroperitoneal space was entered. After the surrounding connective tissue was carefully dissociated and the communicating vessels between the mass and the inferior vena cava and abdominal aorta were ligated, the pregnancy mass was removed en bloc. No blood transfusion was required. The small wound surface on the inferior vena cava was sutured meticulously with absorbable suture to ensure sufficient hemostasis. No retroperitoneal drain was placed. The total blood loss was 50 millilitre (ml) and the operation time was 92 min.

An embryo bud was detected macroscopically inside the resected retroperitoneal mass. Pathological examination confirmed the presence of chorionic villi under an inverted microscope (Olympus, Tokyo, Japan) (Fig. 2).

Serum β-hCG decreased to 21,707 mIU/mL on the first postoperative day and 582 mIU/mL on the 6^th postoperative day. The patient recovered smoothly and was discharged on the 6^th postoperative day. Her serum β-hCG were strictly monitored in the outpatient setting and returned to normal range on the 23^th postoperative day. Changes in the serum β-hCG levels over time are shown in Fig. 3.

Abdominal pregnancy is the rarest type of ectopic pregnancies, possessing eight times higher rates of maternal mortality and morbidity than nonabdominal cases [2]. According to the criteria established by Studdiford in 1942 [6], only a very small fraction of the reported cases could be exclusively diagnosed as primary abdominal pregnancy. Reported common sites of primary abdominal pregnancy are the pouch of Douglas, posterior uterine wall, uterine fundus, anterior abdominal wall, omentum, liver, spleen, and diaphragm [7, 8]. However, abdominal pregnancy in the retroperitoneal space is an exceedingly rare occurrence. Due to its rarity, it is impossible to accurately calculate the incidence of REP. Given its propensity to implant along major vessels, REP poses a high risk of fatal rupture and bleeding. To date, however, there is no well-defined consensus or guideline for clinical management. Bizarre implantation locations, non-specific symptoms and varied clinical presentations can make the diagnosis and treatment of REP challenging, sometimes resulting in misdiagnosis. In order to better guide clinical practice, we conducted a search of PubMed database (English language; 1970–2022; search terms: “retroperitoneal ectopic pregnancy” and “retroperitoneal pregnancy”), and supplemented related cases through literature tracking. A total of 31 literatures including 32 REP cases, plus the case presented here, were collected and thoroughly analyzed, focusing on the clinical characteristics, diagnosis, treatment and prognosis (details listed in Table 1 [4, 5, 9‐37]).