The Reliability of 3-Dimensional Endoanal Ultrasonography Early and Late Postpartum.

Importance: There is no consensus on how to define obstetric anal sphincter defects detected by 3-dimensional endoanal ultrasonography (3D-EAUS), and the reported rates vary significantly in the postpartum period.

Objective: The objective of this study was to establish a diagnostic strategy with a high and clinically relevant interrater reliability both early and late postpartum.

Study design: The study was prospective and observational, and 3D-EAUS was performed 10-14 days and 9-12 months postpartum in an unselected cohort of primiparous women with vacuum-assisted deliveries. Two experienced examiners evaluated the ultrasonographic results, which were divided into the categories intact, inconclusive, small, moderate, and large defects based on Starck scores. Three different diagnostic strategies were validated, and the prevalence- and bias-adjusted kappa (PABAK) values calculated.

Results: Of 334 eligible women, 184 (55.1%) completed both examinations. Disagreements involving small defects were predominant and observed in 34 and 39 cases, respectively, at the 2 time points. The highest overall agreement rates (91.3% and 92.4%, respectively) and PABAK values (0.83 and 0.85, respectively) were reached when the disagreements were minimized by dichotomizing the results into Starck scores >4 (designated a significant defect) versus Starck scores 0-4 (all others).

Conclusions: The interrater reliability of detecting small anal sphincter defects by 3D-EAUS was low at both time points for the 2 experienced raters. In contrast, the interrater reliability of detecting a significant defect was classified as almost perfect agreement at both time points.