Intra‐ and interobserver variability in nodule size of rectosigmoid endometriosis measured by two‐ and three‐dimensional transvaginal sonography

INTRODUCTION: The aim of the study was to assess the intra- and interobserver variability of two- and three-dimensional rectosigmoid nodule size measurements by transvaginal sonography in patients with rectosigmoid endometriosis. MATERIAL AND METHODS: Intra- and interobserver variability was assessed in 10 and 30 patients, respectively. Measurements in two dimensions were performed in real-time during the scan, and three-dimensional measurements of volume were done on a computer. Differences within and between observers were expressed in absolute units (mm) and percentage (%) of average nodule size. Coefficient of repeatability and Bland-Altman plots with limits of agreement were used to evaluate the intra- and interobserver variability. RESULTS: Intra- and interobserver variability in two-dimensional sonography ranged from 11 to 14 mm (46-51%) for length, 3 to 6 mm (32-57%) for depth and 5 to 9 mm (33-58%) for width of the nodule. Results of three-dimensional sonography, with assessment of nodule volume, showed intra- and interobserver variability 0.4 to 2.5 times the average nodule size. CONCLUSIONS: Measurements of rectosigmoid endometriosis nodule size with two- and three- dimensional transvaginal sonography were associated with large intra- and interobserver variability. These techniques should therefore be used with caution in clinical control and research of nodule growth.