Image-Quality Assessment of the Levator Ani Immediately After Delivery

Vaginal childbirth may cause levator ani muscle (LAM) avulsion and hiatal widening. 3D/4D transperineal ultrasound (TPUS) is widely used to assess the hiatal area and insertion of the LAM. We aimed to assess the quality of TPUS images for assessing the above when acquisitions were done immediately after vaginal childbirth.

Secondary analysis of images obtained after vaginal birth by experienced sonographers, in 100 randomly selected patients from two prospective cohort studies, was carried out. In those, TPUS volumes were acquired immediately after vaginal delivery at rest, during contraction of the pelvic floor muscles, and during Valsalva. Two investigators independently rated the image quality for visibility of midsagittal landmarks (symphysis, urethra, levator ani; yes/no), quality of visualization using a three-point Likert scale of the LAM in the axial plane and on tomographic ultrasound images (TUI), and visualization of the pubic symphysis and insertion points of the LAM. Sixty random volumes with adequate/ideal image quality were selected for intra- and inter-rater agreement of hiatal dimension measurements.

In the midsagittal plane, all landmarks were visible in over 83% of TPUS volumes. "Ideal" or "adequate" visualization of the LAM in the axial plane was achieved in 50% and 40% respectively. Ideal visualization was highest during contraction of the pelvic floor muscles (63%). In TUI, the symphysis was visualized "ideally" or "adequately" in 71% or 22%, right LAM insertion in 73% or 19%, and left LAM insertion in 72% and 20% respectively. Hiatal dimension measurements showed excellent intra- and inter-rater agreement.

The quality of TPUS images obtained immediately after birth was adequate to ideal in over 90% of acquisitions.