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Obstetrics » Obstetrics 1st Trimester
Rupturing ectopic pregnancy
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Presentation A 25 year old female presented with a history of amenorrhea for one month. She now complains of vaginal bleeding and acute left lower quadrant pain. Her urine pregnancy test is positive.
Caption: Transvaginal sagittal sonogram.
Description: Transvaginal scan showing a normal uterine endometrial stripe. The normal right ovary is seen posteriorly, and contains a cystic structure, likely a corpus luteum.
Caption: Transvaginal transverse view of the right adnexa.
Description: Transverse view of the right adnexa showing the ‘tubal ring’ sign. No fetal parts seen. This was the abnormal gestation sac measuring 4x4x4 mm, consistent with an estimated gestational age of 5.2 weeks. Complex free fluid seen to the left of the sac.
Caption: Sagittal view of the right adnexa and cul-de-sac.
Description: This transvaginal sagittal view shows a considerable amount of echogenic fluid, consistent with blood. The amount of fluid kept increasing during the scan, consistent with acute bleeding.
Caption: Color Doppler view of the right adnexa.
Description: Color Doppler demonstrating the adnexal mass to be avascular, suggestive of a non-viable ectopic gestation.
Differential Diagnosis Ectopic pregnancy [a rupturing corpus luteal cyst would be the closest differential, however the thick tubal ring seen in this case strongly favors ectopic gestation as the diagnosis].
Final Diagnosis Rupturing ectopic pregnancy.
Discussion Ectopic pregnancy is a dreaded complication in the reproductive age group. It is the implantation of the conceptus outside of the normal uterine cavity site. Many factors are implicated in the development of an ectopic pregnancy. These include prior ectopic, tubal scarring due to PID or surgeries and in-vitro fertilization treatments. The most common implantation site is within the fallopian tube.  Other sites include cervical, ovarian, cornual and rarely abdominal. Early recognition of ectopic is essential in order to prevent catastrophic events.

Ectopic pregnancy should be considered when a female presents with vaginal bleeding, usually in the first trimester, pelvic pain and a palpable adnexal mass, although all the signs may not be present every time. If the ectopic is ruptured, the patient may present with signs of shock. With an ectopic, no evidence of intrauterine pregnancy would be noted on ultrasonography. A normal gestational sac is covered by decidua capsularis and is embedded eccentrically within the decidua parietalis, giving the appearance of double decidual sign, which is a reliable indicator of normal IUP. Studies also report the presence of the “intradecidual sign”, which is an echogenic, thick-walled sac seen within a thickened endometrium, as an earlier indicator for IUP. With ectopic pregnancy, the uterus is most commonly normal, made conspicuous by the absence of the double decidual sign. A pseudo- gestational sac may be present, which consists of intrauterine fluid collection surrounded by single decidual layer.

Usually a complex cystic adnexal mass separate from the ovary is seen, which may or may not demonstrate a live embryo, with cardiac activity. Free fluid may be noted, which if echogenic, is suggestive of hemoperitoneum. An ectopic tubal ring has been described in 49% of ruptured ectopics and in 68% of unruptured ectopics. The tubal ring consists of concentric trophoblastic tissue surrounding the chorionic sac of the ectopic pregnancy. It is usually seen as a variable sized mass, consisting of a hypoechoic center and surrounded by a thick echogenic rim. This tubal ring can be used to distinguish an ectopic from a ruptured corpus luteum cyst, which is its closest differential. The corpus luteum cyst is located eccentrically within the ovarian tissue.

Color Doppler study reveals a highly vascular ‘ring of fire’ appearance surrounding the tubal ring, confirming that the cystic adnexal mass is an ectopic gestational sac. This appearance is due to a high velocity, low resistance, and trophoblastic flow through the feeding branch of the uterine artery on the affected tubal gestation site, which may aid in narrowing the differential, leading to early detection of the condition. Identification of the echogenic chorionic rim with low resistance flow favors an ectopic pregnancy over a corpus luteum cyst. Color Doppler studies have been reported to improve the diagnostic sensitivity and specificity of ultrasound in diagnosing ectopic gestation. In the case shown here, the ectopic gestation was dead, and hence no vascularity was noted. MRI may play some role in the diagnosis of this entity when ultrasound studies are insufficient or equivocal.

As was noted in our case, the amount of free fluid kept increasing as the patient was being scanned, suggesting the ominous diagnosis of a rupturing ectopic pregnancy.

Case References 1.Fleischer AC, Pennell RG, et al :Ectopic pregnancy: features at transvaginal sonography. Radiology. 1990 Feb; 174(2): 375-8.
2.Rottem S, Thaler I, et al : Criteria for transvaginal sonographic diagnosis of ectopic pregnancy. J Clin Ultrasound. 1990 May; 18(4): 274-9.
3.Kirchler HC, Kolle D, Schwegel P.: Changes in tubal blood flow in evaluating ectopic pregnancy. Ultrasound Obstet Gynecol. 1992 Jul 1; 2(4): 283-8.
4.Szabo I, Csabay L, et al: Assessment of uterine circulation in ectopic pregnancy by transvaginal color Doppler. Eur J Obstet Gynecol Reprod Biol. 2003 Feb 10; 106(2): 203-8.
5.Pellerito JS, Taylor KJ, et al: Ectopic pregnancy: evaluation with endovaginal color flow imaging. Radiology. 1992 May; 183(2): 407-11.
6.Nyberg DA, Laing FC, Filly RA, et al.: Ultrasonographic differentiation of the gestational sac of early intrauterine pregnancy from the pseudogestational sac of ectopic pregnancy. Radiology, 146; 755-761, 1983.
Follow Up This patient was taken for emergency surgery, and the ruptured ectopic gestation was removed.
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