Retrospective image observation of ectopic pregnancy on computed tomography in the emergency condition: How useful is adnexal ring sign?

Ectopic pregnancy is a major cause of first-trimester death in pregnancy, and standard clinical assessments continue to rely on hormonal assays and pelvic sonography. Although the adnexal or tubal ring sign is a diagnostic feature of ectopic pregnancy on pelvic sonography, it has not been well recognized on computed tomography (CT) due to radiation concerns. However, CT is increasingly being used in emergency situations where the patient's medical history is unknown or unavailable. Further, it can be unintentionally performed on a pregnant patient. The aim of this retrospective study is to determine the diagnostic value of the adnexal ring sign on contrast-enhanced CT. In this review, we included 877 cases of pathologically proven ectopic pregnancy recorded between January 2003 and December 2012, among which 14 underwent abdominal CT before surgery. Next, the images and surgical findings were retrospectively analyzed to assess the correlation between the adnexal ring sign on CT and the presence of ectopic pregnancy. The adnexal ring sign was positive in 11 of 14 surgically proven ectopic pregnancies. The sensitivity and specificity of the adnexal ring sign under CT scan were calculated as 78.6% and 92.3%, respectively, and the positive and negative predictive values were 91.7% and 80.0%, respectively. The likelihood ratio (sensitivity/[1-specificity]) was 10.2. In conclusion, our study supports the contention that the CT adnexal ring sign correlates with the presence of ectopic pregnancy. The presence of CT adnexal ring sign with hemoperitoneum and an increase in human chorionic gonadotropin should strongly suggest the diagnosis of ruptured ectopic pregnancy.