MR Imaging for Ectopic Pregnancy

Abstract

Ectopic pregnancy (EP) is diagnosed based on laboratory values and ultrasonography (US) findings. Evaluation for suspected EP should begin with a quantitative measurement of the serum β-human chorionic gonadotropin levels and transvaginal US. MR imaging is not preferentially performed in the evaluation of EP; however, if the findings of transvaginal US are uncertain, MR imaging can be used, as it has the advantages of superior soft-tissue contrast resolution and a wide scanning range. Identifying the exact location of implantation transfer using MR imaging can help in the diagnosis and establishment of treatment strategies for ectopic pregnancies, including laparoscopy. In particular, as the incidence of heterotopic pregnancy has increased with the recent increase in use of assisted reproductive technology, the scope of application of MR imaging is expected to expand further. This pictorial essay describes the various manifestations of EP and related conditions on MR imaging and US. Familiarity with the clinical setting and the US and MR imaging features of EP and associated conditions can lead to a more accurate diagnosis and treatment.

Keywords: Ectopic Pregnancy; Heterotopic Pregnancy; Magnetic Resonance Imaging; Ultrasonography.

Fig. 1. US feature of ectopic pregnancy: decidual cyst.

The sagittal transvaginal view of the uterus shows a small fluid collection at the junction of the endometrium and myometrium (arrow).

Fig. 2. US feature of ectopic pregnancy: pseudosac.

A sagittal transvaginal scan of the uterus shows a small, centrally located fluid collection with internal blood and debris in the endometrial cavity.

Fig. 3. US feature of ectopic pregnancy: live extrauterine embryo.

A, B. Transvaginal view with m-mode shows embryo (calipers) with normal cardiac activity (arrows).

Fig. 4. US feature of ectopic pregnancy: tubal ring sign.

A, B. Transvaginal view of the uterus and right ovary shows an extrauterine mass (calipers) with thick echogenic wall. Note that the mass moves separately from the ovary.

Fig. 5. US feature of EP: the “ring-of-fire” sign.

Color Doppler US shows increased blood flow around an EP. EP = ectopic pregnancy

Fig. 6. US feature of ectopic pregnancy: tubal mass.

Transvaginal scan shows a nonspecific mass with heterogeneous echogenicity.

Fig. 7. US feature of ectopic pregnancy: hemoperitoneum.

Transabdominal view of the pelvis shows large amount of free fluid with mixed echogenicity.

Fig. 8. MR imaging findings in a 40-year-old woman with ectopic pregnancy.

A. Transverse T2-weighted imaging shows a thick-walled cyst (arrow), indicating extrauterine gestational sac and a “three-ring sign.” B, C. Diffusion-weighted imaging (B) and apparent diffusion coefficient map (C) show a “ring-of-restriction” sign (arrows).

Fig. 9. MR imaging findings in a 42-year-old woman with chronic pelvic pain for 1 year and low level of β-human chorionic gonadotropin elevation.

A-C. Transverse T2WI (A), transverse contrast-enhanced-T1WI (B), and coronal T2WI (C) show a heterogeneous mass in the pelvis. The combined left tubal dilatation and enhancement are shown. A few chorionic villi in a hemorrhagic background at the left adnexa are consistent with ectopic gestation. WI = weighted imaging

Fig. 10. MR imaging findings in a 32-year-old woman with sudden abdominal pain due to heterotopic pregnancy. She had undergone in vitro fertilization and embryo transfer and had a twin pregnancy (gestational age: 7 weeks).

A. Transvaginal sonogram shows normal IUP (calipers). B. Transverse T2WI shows IUP (P) and small hemoperitoneum (F). C, D. Transverse (C) and sagittal (D) T2WI show right-sided ectopic pregnancy (arrows) and small hemoperitoneum (F). IUP = intrauterine pregnancy, WI = weighted imaging

Fig. 11. MR imaging findings in a 27-year-old woman with right lower quadrant pain for 1 day.

A. Transvaginal US demonstrates an intrauterine GS. B-D. Transverse and coronal T2-weighted imaging show an endometrial GS (P) and another GS (arrows) in the right interstitium of the uterus, suggesting interstitial and heterotopic pregnancy. A large amount of hemoperitoneum (*) at the right paracolic gutter is evident. MR imaging can detect EP and intrauterine pregnancy. E. Laparoscopy shows an EP (arrow) in the right interstitium of the uterus with active bleeding. Hemoperitoneum in the pelvis to the upper liver dome is also evident. EP = ectopic pregnancy, GS = gestational sac

Fig. 12. MR imaging finding in a 28-year-old woman with abdominal EP.

Coronal T2-weighted imaging shows a well-defined cystic lesion with a thick peripheral wall (arrow) in the lateral aspect of the ascending colon, suggested to be the focus of the EP. Adapted from Kim et al. Abdom Radiol (NY) 2022;47:2254-2276, with permission of Springer Nature (20). EP = ectopic pregnancy