Transvaginal ultrasound assessment of uterine scar after previous caesarean section: comparison with 3T-magnetic resonance diffusion tensor imaging

This study aimed to evaluate 3-T magnetic resonance imaging in the analysis of caesarean scars in women with prior caesarean section (pCS) and investigate the potential added value of diffusion tensor imaging (3T-MR-DTI) with fibre tracking reconstruction, compared with transvaginal ultrasound (TVUS). Thirty women who had previously undergone elective CS in a singleton pregnancy at term were examined (19 women with one pCS formed group 1 and 11 women with two pCS formed group 2). Patients underwent TVUS and 3T-MR-DTI within 2 days. Twelve women with prior vaginal delivery served as controls and underwent only 3T-MR. Uterine fibre architecture was depicted by MR-DTI with 3D tractography reconstruction providing quali-quantitative analysis of fibre, described as the reduction of number of longitudinal fibres that run through the uterine scar. Six subjects were excluded. According to 3T-MR morphology, scars were described as linear (n = 12) and retracting (n = 12); disagreement with TVUS was 54 %. The thickness of myometrium at the scar level was found to be significantly greater with 3T-MR compared to TVUS in linear scars (p = 0.01). No difference was found among retracting scars. In controls, according to 3T-MR-DTI, longitudinal myometrial fibres running in the anterior wall were similar to those in the posterior wall at same level -2 %; -27 % + 22 %). In groups 1 and 2 there was significant reduction in anterior fibres compared to posterior ones (-53 %; -77 % - 34 %; p = 0.0001). Among retracting scars, fibre reduction was significantly higher compared to linear scars, p < 0.016. The added value of 3T-MR with DTI lies in the prompt evaluation of muscle fibre remaining at scar level.