To investigate the image features and diagnostic values of transvenous contrast-enhanced ultrasonography (CEUS) in patients with bursa type of cesarean scar pregnancy (CSP).

From February 2012 to January 2017, a total of 31 pregnant women with bursa type of CSP which suspicion diagnosed clinically in West China Second University Hospital, Sichuan University, were chosen as research objects. Conventional ultrasonography and transvenous CEUS were performed to all patients at the same time. First, conventional ultrasonography was performed to discover the suspected CSP lesion and determine the observation view at CEUS. Then, after ultrasound microbubble contrast agents were bolus intravenous injected via elbow vein, real-time dynamic imagings of CEUS were observed in suspicion lesion of CSP. Took patients＇ own myometrium as reference, to observe the first position, the earliest time, the intensity of contrast enhancement, the distribution area and the clearance of contrast agent in gestational sac. The histopathological examination results of dilatation and curettage postoperative cleared lesion were taken as the gold standard, and the diagnose accordance rates of conventional ultrasonography with gold standard, transvenous CEUS with gold standard were calculated respectively. Fisher′s exact test was used to compare the difference between these two diagnose accordance rates. This study met the requirements of the World Medical Association Declaration of Helsinki revised in 2013.

①Image characteristics of transvenous CEUS in patients with bursa type of CSP were early enhancement, high enhancement, " semi-ring sign" and slow clearance. Specifically for contrast agents first appearing at the gestational sac close to uterine scar. The first appearing time of contrast agents in gestational sac was earlier than that in patients′ own myometrium. The intensity of contrast enhancement in gestational sac was higher than that in patients′ own myometrium. The " semi-ring" arc hyperenhancement was observed at the early stage of CEUS at uterine scar where the gestational sac was implanted. The clearance and regression time of contrast agents at the lesions of gestational sac was later than that of patients′ own myometrium. ②The conventional ultrasonography results of 31 patients with clinical suspicion diagnosed as bursa type of CSP were all bursa type of CSP. Gold standard and transvenous CEUS results of these 31 patients were the same that 26 cases were bursa type of CSP, 4 cases were low position of gestational sac (non-CSP), and 1 case was inevitable abortion. The results showed that the diagnose accordance rate of conventional ultrasonography with gold standard was 83.9%(26/31) while the diagnose accordance rate of transvenous CEUS with gold standard was 100.0%(31/31). The former has a lower diagnose accordance rate than the latter, and the difference was statistically significant (P=0.026).

Transvenous CEUS for bursa type of CSP has characteristic image features to make a definite diagnosis so that the clinicians can take reasonable treatment measures to prevent pregnant women from hemorrhea during curettage.