A case of retroperitoneal para-aortic ectopic pregnancy
detected by sonography
Min Zhang MD
Ling-Ling Qin MD
Department of Ultrasonography,
Hainan General Hospital, Haikou, China
Department of Ultrasonography,
Hainan General Hospital,
Haikou 570311, China.
Retroperitoneal ectopic pregnancy is extremely rare. We present a case of a retroperitoneal
ectopic pregnancy with a gestational sac located to the left of the abdominal aorta and of the left
renal vessels at 9 weeks of gestation. Careful transabdominal sonographic examination is sug-
gested when an ectopic pregnancy is suspected and the examination of the pelvis is negative.
ectopic pregnancy, retroperitoneum, ultrasound
Abdominal pregnancies account for 1% of all ectopic pregnancies, and
retroperitoneal location is a rare form of abdominal pregnancy.
diagnosis is often missed because the early symptoms and signs are
nonspecific. Gestational sacs often implant adjacent to large retroperi-
toneal vessels. Once a retroperitoneal gestational sac ruptures, it can
cause a catastrophic hemorrhage. We present a rare case of a retroper-
itoneal para-aortic ectopic pregnancy detected by sonography (ultra-
sound [US]) at 9 weeks of gestation.
A 29-year-old woman was referred to our institution with a 2-month
history of amenorrhea and a 10-day history of left lower flank pain.
The patient’s medical and gynecologic histories were unremarkable.
Physical examination revealed tenderness in the left lower flank. The
hCG level was 16 453 IU/L. US examination was performed using a
Mindray DC-8 scanner (Mindray Medical International Ltd, ShenZ-
hen, China) with a 3.0- to 5.0-MHz convex-array probe and a 3.2- to
7.9-MHz endovaginal probe. Transvaginal US showed endometrial
thickening measuring 22 mm. Neither an intrauterine gestational sac
nor an adnexal mass was identified. There was no free intraperito-
neal fluid. A gestational sac was identified in the retroperitoneal
space of the left abdomen, in the anterior part of the iliac and lumbar
musculature. It was adherent to the left side of the abdominal aorta
and located in front of the origin of the left renal artery (Figure 1A).
The gestational sac measured 41 3 29 mm and contained a visible
yolk sac and an embryo that measured 31 mm in length. The
placental attachment site was close to the left side of the abdominal
aorta (Figure 1B). The embryo size suggested a gestational age of
approximately 9 weeks. The patient was treated with methotrexate
and selective arterial embolization therapy (Figure 2A,B). Ten days
later, US showed that the gestational sac had grown to a size con-
sistent with approximately 11 weeks of gestational age. The embryo
remained viable (Figure 2C,D), and the serum hCG level had risen to
36 312 IU/L. Consequently, a laparotomy was performed. The retro-
peritoneum was intact (Figure 3A). The ectopic pregnancy was
located on the left side of the abdominal aorta. The mass measure
approximately 11 cm in diameter, and it contained a viable embryo.
The upper pole of the mass encased the left renal vessels and
abdominal aorta, with adhesions to surrounding tissues. The gesta-
tional sac was separate from the aorta and the origin of the left renal
artery (Figure 3B). The gestational sac contained an embryo and pla-
cental tissue (Figure 3C).
Retroperitoneal ectopic pregnancy is a very rare type of abdominal
pregnancy. Reported sites include the omentum, paracolic sulcus, ute-
rosacral ligament, infrarenal or infrapancreatic locations, and locations
superficial to the abdominal aorta or the inferior vena cava.
mechanisms have been suggested to explain how retroperitoneal
ectopic pregnancies develop. First, the embryo may be transported
from the uterine cavity to the retroperitoneal space through lymphatic
channels, similar to a metastasis from uterine endometrial cancer.
Alternatively, the embryo may implant on the peritoneal surface at an
injury site (related to endometriosis or inflammation) and then enter
2017 Wiley Periodicals, Inc. wileyonlinelibrary.com/journal/jcu J Clin Ultrasound. 2018;46:412–414.
Received: 23 May 2017
Revised: 14 September 2017
Accepted: 10 October 2017