Contrast enhanced ultrasound - a useful method for diagnosing tubal ectopic pregnancy with low level β-HCG

Abstract

Background: In patients presenting with atypical symptoms or low plasma β-HCG levels, the presence of an adnexal mass without a yolk sac or embryo on ultrasound often provides insufficient confidence for a definitive diagnosis of ectopic pregnancy(EP). Consequently, most such cases can only be classified as suspected EP. This study aimed to evaluate the diagnostic value of contrast enhanced ultrasound (CEUS) for tubal EP (tEP). We retrospectively analyzed 21 patients with suspected EP who underwent CEUS between August 2017 and August 2024. All patients had plasma β-HCG levels below 3500 mIU/mL. Among them, 20 underwent laparoscopic surgery, and all underwent curettage. The diagnostic performance of CEUS for tEP was assessed.

Results: A total of 21 patients were included: 19 with tEP, 1 with ovarian pregnancy, and 1 with intrauterine pregnancy. The sensitivity, specificity, and accuracy of transvaginal ultrasound (TVUS) for diagnosing tubal dilation were 15.8%, 100%, and 23.8%, respectively. For CEUS, these values were 94.7%, 100%, and 95.2%, respectively. Statistically significant differences were observed between CEUS and TVUS in sensitivity and accuracy (P = 0.000). The enhancement pattern of villous tissue was categorized as either circular or non-circular. Among the tEP cases, 2 exhibited circular enhancement and 17 showed non-circular enhancement. Based on positive β-HCG, absence of an intrauterine gestational sac, and sonographic visualization of a dilated fallopian tube containing either circular or non-circular enhancement internally, CEUS demonstrated high diagnostic accuracy for tEP diagnosis in cases with low β-HCG levels. CEUS correctly diagnosed 18 of 19 tEP cases. One tEP case was diagnosed as a mass of uncertain significance. The intrauterine pregnancy case was misdiagnosed as an EP. The ovarian pregnancy case was diagnosed as EP, though CEUS indicated a relatively high possibility of ovarian origin.

Conclusion: In conclusion, CEUS holds significant diagnostic value for tEP. It is particularly useful in diagnostically unclear cases and provides a more detailed assessment of the internal structure of adnexal masses.

Keywords: Contrast media; Ectopic; Fallopian tubes; Pregnancy; Ultrasonography.

Fig. 1

A flow diagram of patient enrollment process

Fig. 2

Transvaginal contrast enhanced ultrasound(CEUS) showed the longitudinal section of the fallopian tube. The patient was a 39-year-old woman who came to the hospital for amenorrhea and vaginal bleeding. Her blood HCG level was 806 mIU/mL. The time interval between CEUS and blood HCG measurement was less than 6h. Ultrasound examination found a low to medium echoic mass measuring 3.6cm × 1.8cm in the right adnexal region (left figure). The CEUS showed heterogeneous enhancement of the mass (right figure). The thick arrow indicated the dilated fallopian tube, and the thin arrow indicated the enhanced villous tissue. The non-enhanced area within the mass was confirmed intraoperatively to be blood clots within the fallopian tube. The villous tissue size visible during the operation was 0.5cm × 0.5cm, similar to the size measured by ultrasound (0.8cm × 0.5cm). The enhancement pattern of this patient was non-annular enhancement.This patient was confirmed by surgery to have a pregnancy in the ampulla of the right fallopian tube. Transvaginal contrast enhanced ultrasound (CEUS) showed the longitudinal section of the fallopian tube

Fig. 3

Transvaginal contrast enhanced ultrasound (CEUS) showed the cross section of the fallopian tube. The patient was 34 years old and came to the hospital due to abdominal pain, amenorrhea, and vaginal bleeding. The blood HCG level was 2165 mIU/mL, and the time interval between the CEUS and the measurement of blood HCG was less than 24 hours. A ring-like slightly high echoic structure (bagel sign) measuring 1.7cm × 1.4cm was visible in the left adnexal region, with a small area of anechoic in the center (left figure). CEUS imaging showed that, some parts of the high echoic ring-like structure enhanced, while other parts were not enhanced (right figure). The thick arrow indicated the dilated fallopian tube, and the thin arrow indicated the enhanced villous tissue. The villous tissue size visible during the operation was 0.5cm × 0.5cm, less than the size measured by ultrasound (0.8cm x 1.0cm).The enhancement pattern of this patient was non-annular enhancement. This patient was confirmed by surgery to have a pregnancy in the ampulla of the left fallopian tube

Fig. 4

Transvaginal contrast enhanced ultrasound (CEUS) showed the longitudinal section of the fallopian tube. The patient was 30 years old and came to the hospital due to abdominal pain, amenorrhea, and vaginal bleeding. The blood HCG level was 929 mIU/mL, and the time interval between CEUS and the measurement of blood HCG was less than 6 hours. A mixed-echoic mass (blob sign) measuring 3.2cm× 1.3cm was seen in the left adnexal region with a portion of the mass demonstrating a bagel sign (arrows on the left and the middle of the left figure). CEUS showed heterogeneous enhancement of the mass. The area with the bagel sign demonstrated ring-like enhancement, while the other areas mainly showed tubular structures without enhancement. The thick arrow indicated the the enhanced villous tissue, the thin short arrow indicated dilated fallopian tube, and the thin long arrow indicated blood clots within the fallopian tube. This patient was confirmed by surgery to have a pregnancy in the ampulla of the left fallopian tube.There was no record of the size of the villous tissue

Fig. 5

Transvaginal contrast enhanced ultrasound (CEUS) showed a adnexal mass of unknown origin. The patient was a 23-year-old woman who presented with amenorrhea and vaginal bleeding. The patient’s blood HCG level was 1010 mIU/mL, and the time interval between CEUS and blood testing was less than 6 h. A mixed echoic mass measuring 2.4 cm×2.1 cm was seen beside the right ovary (left image). CEUS showed heterogeneous enhancement of the mass. The thick arrow indicated the enhanced cyst wall and the thin arrow indicated the enhanced villous tissue (right image). The ultrasound diagnosis was ectopic pregnancy with the location to be undetermined and the possibility of ovarian pregnancy was relatively high. The final surgical diagnosis confirmed it as a right ovarian pregnancy, with the villous tissue measuring 0.8 cm×0.8 cm, similar to the ultrasound measurement (0.8 cm×0.6 cm). The non-enhanced areas within the lesions were surgically confirmed to be blood clots

Fig. 6

Transvaginal contrast enhanced ultrasound(CEUS) misdiagnosed the luteal structure in the ovary as an adnexal pregnancy. This was a case of intrauterine pregnancy misdiagnosed as ectopic pregnancy by CEUS. The patient, a 28-year-old woman, visited the hospital due to abdominal pain. Her blood HCG level was 84 mIU/mL. The left image showed a high-echo mass (thin arrow) near the left ovary (thick arrow), measuring 2.2cm×2.0cm. The right image of CEUS showed significant enhancement of the mass with a crescent moon shape. The enhancement of the ovary was less than the mass. The ultrasound diagnosis was ectopic pregnancy with the location to be undetermined and the possibility of ovarian pregnancy was relatively high. The patient was later confirmed to have anuterine pregnancy. After a curettage, the patients HCG levels returned to normal and no abnormalities were seen in the ovaries