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

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.

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.

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.