12 Color Doppler Sonography in Ectopic Pregnancy

H. J. Voigt

Importance of Transvaginal Sonography and Serum hCG

β-hCG. Various studies have consistently shown that ectopic pregnancy can be diagnosed by transvaginal ultrasound in 80–95% of cases2,9. Nyberg et al.⁷ found associated β-hCG levels of 1000 IU/l or more. Our own studies showed that the chorion could be visualized at β-hCG levels of 500 IU/l in favorable cases and consistently visualized at levels in the range of 1000–2000 IU/l¹⁴. This means that ectopic pregnancy should always be considered in asymptomatic patients with a serum β-hCG level of 1000 IU/l or more who do not have a demonstrable intrauterine chorion, and that further tests should be done to confirm or exclude the diagnosis.

Routine vaginal scans. Rein et al.⁸ state that a vaginal ultrasound examination should be performed routinely in all early pregnancies, since the early diagnosis of ectopic pregnancy can significantly reduce the maternal risk and improve the chances for an organ-conserving laparoscopy. This particularly applies to high-risk patients with a history of infertility or chronic recurring inflammations, IUD (intrauterine device) wearers, and of course women with a prior history of ectopic pregnancy.

Typical sonographic findings. Today the following vaginal ultrasound findings are considered to be definite or compelling evidence of an early ectopic pregnancy (assuming the patient has a positive pregnancy test):

Exclusion of an intrauterine chorion-type structure

Presence of an extrauterine and extraovarian chorion-type structure

Demonstrable embryonic heart activity and movements within the structure (<5% of cases)

Enlarged uterus with a thickened endometrium of high echogenicity

Free fluid in the cul-de-sac and paracolic gutters with clot formation and fibrin strands (hemoperitoneum)

The greater the number of these suggestive findings, the higher the index of suspicion for an ectopic pregnancy.

Differential diagnosis. It is difficult to distinguish a nonintact ectopic pregnancy from an adnexal tumor, because the chorionic cavity cannot always be differentiated from a cystic-solid mass. In this case the clinical presentation and β-hCG progression should be used to confirm the diagnosis.

With its higher resolution, transvaginal sonography does not demonstrate the classic “pseudogestational sac” of ectopic pregnancy that is seen with transabdominal ultrasound. If a ringlike structure is detected in the uterine cavity with transvaginal ultrasound, the differential diagnosis will include a blighted ovum or incomplete abortion, especially if there is associated hemorrhage.

Despite the improved capabilities of current routine studies, ectopic pregnancy continues to pose a diagnostic and therapeutic challenge in both asymptomatic and symptomatic cases.

Application of new techniques. There is no question that improved ultrasound techniques have helped to increase preoperative diagnostic accuracy and reduce the number of unnecessary surgical procedures. Transvaginal color Doppler sonography is an innovative technique that is being tested for its ability to identify extrauterine chorion-like structures based on their increased blood flow and typical peritrophoblastic blood flow patterns.

Transvaginal Color Doppler Sonography

Typical Findings in Normal and Ectopic Pregnancy

Typical Doppler features of the peritrophoblastic region. With the increasing clinical use of transvaginal color Doppler sonography, studies began to be published in the early 1990 s dealing with the circulatory patterns that are typically found in association with early placentation5. Taylor et al.¹² found that the peritrophoblastic region displayed typical Doppler features characterized by a high systolic flow velocity, low impedance, and a high diastolic flow velocity. This suggested the presence of a high pressure gradient between a maternal artery and a perfused area under low pressure, the intervillous space. The normal histomorphological correlate is found in the maternal vessels at the site of placentation. With an ectopic implantation, corresponding signs of early placentation are found until the limitations of the abnormal implantation site put an end to the process and (barring onset of an acute disease process) regressive changes become predominant.

Decreased pulsatile flow in the fallopian tube.

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