Three-Dimensional Transperineal Ultrasound Assessment of the Anal Sphincter Immediately After Vaginal Birth: An Exploratory Study.

Abstract

To assess the feasibility of acquiring adequate transperineal ultrasound (TPUS) volumes of the anal sphincter (AS) immediately after vaginal birth, the reproducibility of its measurements, and detecting defects therein. Secondary analysis of TPUS volumes of the AS, acquired immediately after vaginal birth with a transversely oriented convex probe. Two independent experts ranked off-line image quality as "inadequate," "adequate," or "ideal" using the Point-of-Care Ultrasound Image Quality scale. On "adequate" and "ideal" quality volumes, the length of the external AS at 6 and 12 o'clock, and the volume of the external and internal AS were measured. Additionally, volumes were screened for AS defects on tomographic ultrasound imaging. Subsequently, we rated the intra- and interrater agreement on those findings. Of 183 volumes, 162 were considered "adequate" or of "ideal" quality (88.5%). Reasons for "inadequacy" were shadow artifacts (16/21), poor resolution (3/21), incomplete acquisition (1/21), or aberrant AS morphology (1/21). The intrarater reliability of two-dimensional (2D) and three-dimensional (3D) measurements was excellent, whereas interrater reliability was fair to good for 2D measurements and good for 3D measurements. In those tomographic ultrasound imaging (TUI) sequences including AS defects, the intra- and interrater reliability of the defect measurement were excellent [intraclass correlation coefficient (ICC) = 0.92 (0.80-0.94)] and moderate [ICC = 0.72 (0.63-0.79)]. In this cohort, there were only few (4/48; 8.3%) AS defects. However, grading them was poorly reproducible between experts. TPUS of the AS immediately after vaginal birth yields adequate image quality and allows for reproducible measurements. In the few patients with AS defects, there was good agreement on the presence, but it was poor for the extent of defects.