High frequency ultrasound scan of lower uterine segment during the third trimester of scar uterus pregnancy: Imaging features and impiications / 第二军医大学学报

ABSTRACT

Objective To use high frequency ultrasound for scanning the lower uterine segment during the third trimester of scar uterus pregnancy cases were selected. Transabdominal ultrasound scan was done for the fetus between 36th and 40th week of pregnancy, and then the transducer was switched to a high frequency of 7.5-12 MHz to observe the lower uterine segment. The scan results were compared with the obserbations of in complete rupture of lower uterine segment and defective scars in the repeated caesarean section. Results Three types of high frequency ultrasound images were found for the lower uterine segment during the third trimester of scar uterus pregnancy efficacies of truncation sign (608%,8/118), rat tail sign (44.1%,52/118), and homogeneous echoes (49.1%.58/118). The diagnosis efficacies of truncation sign for incomplete rupture of uterus, rat tail sign for defective scars, and homogeneous echoes for intact cadsarean scars were significantly higher than those of the other two types (X2 valued 20.42, 19.03, and 33.08, respectively, P<0.001). The diagnostic sensitivity, positive predictive value and negative predictive value of the truncation sign were 80.0%, 96.5%, 50.0%, and 99.0%; those of the rat tail sign were 70.0%, 73.8%, 67.3%, and 76.2%; and those of homogeneous echoes were 72.9%, 74.1%, 74.1%, and 73.3%, respectively. Conclusion High frequency ultrasound scan can display the changes of the scars on the lower uterine segment, and may serve as an effective method to diagnose incomplete rupture of uterus, defective and intact scars in the third trimester pregnancy of a caesarean-scarred uterus. To avoid uterine rupture, vaginal trail of labor should be carefully chosen for patients shoeing truncation sign or rat tail sign.