Cesarean section scar measurements in non-pregnant women using three-dimensional ultrasound: a repeatability study

Abstract Objective To evaluate intra- and inter-observer agreement in measurements of the cesarean scar niche and the residual myometrial thickness (RMT) using 3-dimensional (3D) transvaginal ultrasonography. Study design Fifty-eight uterine 3D volumes from women with deep cesarean scar niches were evaluated. 3D volumes were obtained six to fifteen months after a primary cesarean section. Evaluation of the 3D volume was performed in a standardized multiplanar view. Two observers independently obtained RMT, cesarean scar niche depth ( D ), length ( L ), width ( W ), and myometrium adjacent to the scar ( M ). Differences within and between observers were expressed in mm and were evaluated according to the Bland–Altman method including the calculation of limits of agreement (LOAs). Results The intra-observer LOAs in mm were as follows: RMT: −3.7 to 4.0; D : −2.2 to 2.6; L : −3.6 to 4.2; W : −4.0 to 3.7; and M : −3.4 to 4.5. The inter-observer LOAs in mm were as follows: RMT: −3.2 to 4.1; D : −3.3 to 2.2; L : −3.4 to 4.2; W : −3.2 to 4.1; and M : −4.1 to 3.2. Conclusions In non-pregnant women, we found rather wide limits of agreement measuring the cesarean section scar niche and myometrium using 3D volumes. Whether 3D transvaginal ultrasonography provides clinical advantages compared to 2D TVU needs clarification.