Ectopic Pregnancy – The Tubal Ring Sign, Ring of Fire, and Pseudogestational Sac

History 28 year old female presenting with right lower quadrant pain. Positive urine pregnancy test.

Ectopic Pregnancy (Tubal Ring and Ring of Fire): Sagittal endovaginal ultrasound of the right adnexa with color doppler shows two round hypoechoic heterogeneous masses. The mass on the left side of the image is a corpus luteum (with a classic “ring of fire” pattern on doppler flow), and the mass near the center of the image with increased vascularity (the tubal ring sign) is worrisome for a tubal ectopic pregnancy.

Ectopic Pregnancy (pseduogestational sac sign): Sagittal endovaginal ultrasound image of the uterus shows a hypoechoic fluid collection in the endometrial cavity.

This is a case of a tubal ectopic pregnancy. The differential diagnosis in this case includes corpus luteum of pregnancy, incidental adnexal mass, and intrauterine pregnancy. A corpus luteum of pregnancy will typically show the classic “ring of fire” pattern, which is seen in the first image above in the ovary on the left side of the image. The separate round mass with a ring of hypervascularity demonstrates a classic tubal ring sign, which identifies the actual ectopic pregnancy. The best negative predictor of an ectopic pregnancy is an intrauterine pregnancy, however, one has to be careful to not fall for the psuedogestational sac sign, as seen in the second image above, where a fluid collection in the uterine cavity simulates a gestational sac. Most ectopic pregnancies (95%) occur in the fallopian tube. About 1.5% of pregnancies are ectopic pregnancies.

Credit to Paul Murphy, M.D., Ph.D. for this interesting case!