eMedicine Specialties > Radiology > Obstetrics/Gynecology
Ectopic Pregnancy: Imaging
Updated: Jul 18, 2008
Radiography
Findings
No clinically useful plain radiographic findings of ectopic pregnancy have been identified. The associated ionizing radiation poses a hazard if a normal intrauterine pregnancy is present.
Computed Tomography
Findings
CT scan findings are nonspecific for ectopic pregnancy. The associated ionizing radiation poses a hazard if a normal intrauterine pregnancy is present. CT scanning is typically not an appropriate imaging modality to be used for the analysis of ectopic pregnancy.
Magnetic Resonance Imaging
Findings
Axial T2-weighted fast spin-echo magnetic resonance image of the pelvis (same patient as in Images 11-14). This image shows an abnormal fluid-containing fallopian tube (red arrow) on the right side. A simple right ovarian cyst (white arrow) is also present.
Axial T2-weighted fast spin echo magnetic resonance image of the pelvis (same patient as in Images 11-14). After 1 week of conservative therapy, the ectopic pregnancy in Images 11-12 ruptured. A large, mixed-signal-intensity hematoma is now present in the rectouterine pouch (noted by the H and arrows).
Axial T2-weighted gradient-echo magnetic resonance image of the pelvis (same patient as in Images 11-14). After 1 week of conservative therapy, the ectopic pregnancy in Images 11-12 ruptured. A large mixed-signal-intensity hematoma is now present in the rectouterine pouch (noted by the H and arrows).
MRI findings that can suggest an ectopic pregnancy include the presence of (1) a tubal gestational sac; (2) a tubal hematoma, which is a hematoma suggested by the ring sign (peripheral hyperintensity) on T1-weighted images; (3) tubal wall enhancement; and (4) an adnexal mass with hemorrhagic fluid in the peritoneum. Blood is suggested by the presence of high-signal-intensity fluid on T1-weighted images.
Degree of Confidence
MRI should be used only as a problem-solving tool in the patient who is in stable condition. This imaging modality is accurate in the characterization of tissue and in the detection and age determination of blood products.
On MRI, high T1 signal intensity fluid in a fallopian tube is abnormal.13 With a positive beta-HCG result, this finding suggests an ectopic pregnancy. Subacute blood products associated with an adnexal mass are also indicative of an ectopic pregnancy. MRI can additionally delineate confounding adnexal findings seen on ultrasonography, such as follicular or corpus luteum cysts.
Related eMedicine topics:
Ovarian Cysts
Pregnancy, Ectopic
False Positives/Negatives
Early intrauterine pregnancy or a missed abortion may be associated with normal MRI findings and thus falsely suggest an ectopic pregnancy. However, this scenario is not likely because of the high sensitivity of MRI in detecting associated fluid and blood products with true ectopic pregnancies.
The appearance of an adnexal mass is not necessarily specific on MRI. Corpus luteum cysts and other masses may be confused with ruptured or unruptured ectopic pregnancy. False-positive results can be caused by abnormal tubal fluid or enhancement, as seen with pelvic inflammatory disease and simple hydrosalpinx; however, these findings should be correlated with a positive beta-HCG.
Ultrasonography
Findings
Sagittal endovaginal sonogram of the uterus (same patient in Images 1-3). This image shows no evident intrauterine pregnancy.
Endovaginal sonogram (same patient in Images 1-3). This image shows a coronal view of the adnexa. Hypoechoic fluid surrounds the fallopian tube.
Endovaginal sonogram (same patient in Images 6-9). This image shows a coronal view of the right ovary. A corpus luteum cyst mimics an ectopic pregnancy. The cursors denote a hyperechoic clot within the cyst.
Endovaginal sonogram (same patient in Images 6-9). This image shows a sagittal view of the right ovary. A corpus luteum cyst mimics an ectopic pregnancy. The cursors denote a hyperechoic clot within the cyst. Note the thin rim of ovarian tissue surrounding the cyst.
Endovaginal sonogram (same patient in Images 6-9). This image shows a coronal view of the right adnexa. In this patient, the true ectopic pregnancy is identified as a large, heterogeneous adnexal mass surrounded by free fluid.
Findings of an extrauterine ectopic pregnancy include the following:
- Live, extrauterine embryo
- Absence of an intrauterine gestational sac
- Free fluid (particularly hemorrhagic) in the pelvis or peritoneum
- Adnexal mass14
- Hematosalpinx
- Adnexal ring sign and a "ring-of-fire" sign on color Doppler ultrasonographic images (see Images below and Images 3 and 10 in Multimedia)15
Endovaginal sonogram (same patient in Images 1-3). This image shows the tubal ring sign as well as diffuse thickening of the fallopian tube wall with minimal surrounding free fluid.
Endovaginal sonogram. This view shows a color Doppler image of the adnexa with the ring-of-fire sign. Marked hyperemia is present throughout the wall of an enlarged fallopian tube.
- Absence of low-resistance endometrial arterial flow, which is an endometrial color Doppler ultrasonographic finding that is highly suggestive of intrauterine pregnancy
Findings of an interstitial ectopic pregnancy include the following:
- Eccentric location of the gestational sac
- Thinning or the absence of myometrium surrounding the sac
- Interstitial-line sign, or a hyperechoic line extending from the central endometrial cavity to the peripheral interstitial pregnancy, which is created by the interstitial portion of the endometrium or fallopian tube
Degree of Confidence
When correlating beta-HCG levels with ultrasonographic findings, it is important to take into account the standard of measurement. Both the 2IS and IRP systems are used to report beta-HCG values. An IRP value is approximately twice the corresponding 2IS value.
With a positive beta-HCG level greater than 1000 IU/mL (2IS standard) or 2000 IU/mL (IRP standard), a gestational sac should be identifiable within the uterus on transvaginal sonograms.14,16,17 For TA scanning, a higher threshold of 1800 IU/mL (2IS standard) or 3600 IU/mL (IRP standard) should be used. An intrauterine pregnancy can be definitely diagnosed by the double-decidual-sac sign or by the demonstration of an embryo with a positive heartbeat. Cardiac activity should be identifiable in a fetus when it is found within a gestational sac during transvaginal ultrasonography with a mean diameter of 16 mm or a crown-rump length of 5 mm.18
If an intrauterine gestational sac is not found, an ectopic pregnancy must be considered. If the patient's beta-HCG concentration is below the threshold level and if the only finding is the lack of an intrauterine gestational sac, serial follow-up examinations and beta-HCG determinations are required. A normal intrauterine pregnancy should demonstrate a beta-HCG doubling time of 48 hours.4 Below the threshold level, ultrasonography does not aid in differentiating an early intrauterine pregnancy, a missed abortion, and an ectopic pregnancy.
The double decidual sac found with an early intrauterine pregnancy can be difficult to distinguish from the pseudogestational sac, which is seen in 20-50% of ectopic pregnancies. The double decidual sac is 2 concentric hyperechoic rings created by hypoechoic fluid between the decidua parietalis and the decidua capsularis. This sign is in distinct contrast to a single hyperechoic layer found with a pseudogestational sac (see Image below and Image 6 in Multimedia). The lack of a yolk sac, the more-irregular contours, and the more-central location within the endometrial cavity also help in delineating a pseudogestational sac from an early intrauterine pregnancy.
Endovaginal sonogram (same patient in Images 6-9). This image shows a sagittal view of the uterus with a pseudogestational sac. Reactive changes secondary to an ectopic pregnancy are seen as hypoechoic material within the endometrial canal, which is outlined by a single hyperechoic rim. This should be contrasted with the dual hyperechoic lines that represent the dual decidual sac, an indicator of a normal intrauterine pregnancy.
Further support of a pseudogestational sac can be demonstrated by the absence of low-resistance endometrial arterial flow on color Doppler ultrasonographic evaluation. The low pulsatility and the low-resistance flow are highly suggestive of an intrauterine pregnancy. This low-resistance flow should have a resistive index less than 0.6 or a peak systolic frequency of 0.8 kHz or greater.2,19
The combination of the Doppler and ultrasonographic findings should be used to differentiate the early intrauterine pregnancy from a pseudogestational sac. However, Doppler ultrasonographic evaluation has not been shown to be of value when attempting to delineate an adnexal ectopic pregnancy from a corpus luteum cyst, particularly as corpus luteum cysts can demonstrate marked peripheral color Doppler ultrasonographic signal, simulating the ring-of-fire' sign (see Image 10). The intraovarian location is the main factor in distinguishing a corpus luteum cyst.
The only specific sign of an ectopic pregnancy is the presence of a live extrauterine gestation. Free fluid is nonspecific and may present as anechoic or echogenic and in varying amounts. Simple free fluid and an empty uterus have a sensitivity of only 63% and a specificity of only 69%.18 However, hyperechoic fluid and/or large amounts of free fluid are more suggestive of an ectopic pregnancy.4,20
The remaining signs seen in ectopic pregnancy lack sufficient sensitivity and specificity to be used as sole indicators. Because of the variety of ultrasonographic findings, these must be correlated with the clinical presentation and further evaluated to differentiate a possible ectopic pregnancy from an alternate diagnosis.
There are no clear guidelines regarding if or when follow-up sonograms should be obtained. Follow-up examinations should be performed on an individual case basis, in coordination with patient's the clinical scenario and the beta-HCG levels.
False Positives/Negatives
False-positive ultrasonographic findings may be due to a missed abortion or an early normal intrauterine pregnancy (<4.5 wk), without or with secondary findings of an adnexal mass. The latter scenario may include an intrauterine pregnancy with a hemorrhagic corpus luteum cyst or an intrauterine pregnancy with an adnexal mass, as can be found with concurrent appendicitis.
False-negative findings may be due to an intrauterine decidual reaction pseudosac that simulates an early intrauterine pregnancy. Approximately 8% of proven ectopic pregnancies are ultrasonographically normal on retrospective evaluation.2 A concomitant intrauterine pregnancy and ectopic pregnancy (particularly in infertility patients) are other causes of false-negative findings for ectopic pregnancy.
As a note of caution, the limited far field of transvaginal ultrasonography can occasionally miss an ectopic pregnancy that is in a high position. Analysis of the patient's symptoms and placing a transducer on the area of maximal pain may aid the examination. The TA probe can help with this and provide a more global view of the pelvis and its contents.
Nuclear Imaging
Findings
No clinically useful nuclear medicine studies have been identified for ectopic pregnancy.
Angiography
Findings
No clinically useful angiographic findings of ectopic pregnancy have been identified. The associated ionizing radiation poses a hazard if a normal intrauterine pregnancy is present.
More on Ectopic Pregnancy |
| Overview: Ectopic Pregnancy |
 Imaging: Ectopic Pregnancy |
| Follow-up: Ectopic Pregnancy |
| Multimedia: Ectopic Pregnancy |
| References |
| Further Reading |
| « Previous Page | Next Page » |
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Further Reading
Clinical guidelines:
Undifferentiated vaginal bleeding/abdominal pain suggestive of ectopic pregnancy clinical pathway. Maine Medical Center, Department of Emergency Medicine - Hospital/Medical Center. 2006 Aug. Various pagings. NGC:005248
Medical management of ectopic pregnancy. American College of Obstetricians and Gynecologists - Medical Specialty Society. 1998 Dec (revised 2008 Jun). 7 pages. NGC:006533
Clinical studies:
Two-Dose Methotrexate for Ectopic Pregnancy
Ectopic Pregnancy Biomarkers
Risk Factors of Ectopic Pregnancy
Evaluation of Therapeutic Strategies for Treatment of Ectopic Pregnancies (EP) and Evaluation of Subsequent Fertility
Keywords
ectopic pregnancy, ectopic gestation, extrauterine gestation, heterotopic pregnancy, metacyesis, eccyesis, interstitial ectopic, cornual ectopic, cervical ectopic, fimbrial ectopic, ovarian ectopic, ovarian pregnancy, peritoneal ectopic, tubal pregnancy, abdominal pregnancy, pelvic inflammatory disease
