Three-dimensional sonography for diagnosis of rectovaginal septum endometriosis: interobserver agreement

The aim of this study was to evaluate the interobserver agreement for diagnosis of deep endometriosis of the rectovaginal septum using introital 3-dimensional (3D) sonography.

Two experienced observers (observers A and B) performed a retrospective review of stored 3D sonographic volumes from a sample of 84 consecutive patients with a clinical suspicion of endometriosis. Each observer, independently and blinded to each other, evaluated the presence or absence of involvement of the rectovaginal septum. When no lesion was seen, the observers were asked to judge whether the acquisition of the volume was suboptimal for interpretation or whether no lesion on the rectovaginal septum was detectable. One inadequate acquisition case was discarded; a total of 83 cases were evaluated. To calculate the performance of introital 3D sonography, 7 discordant cases were reviewed by a third observer. Interobserver agreement was assessed by calculating the κ index, and the sensitivity, specificity, positive predictive value, and negative predictive value for the 3 observers were also determined.

Interobserver agreement was 0.816 (95% confidence interval, 0.69-0.93), representing very good agreement. Sensitivity was 74.1%; specificity, 85.7%; positive predictive value, 71.4%; and negative predictive value, 87.3%.

Our results show that introital 3D sonography for diagnosis of deep endometriosis of the rectovaginal septum is reproducible, with very good interobserver agreement.