Pelvic floor muscle injuries 6 weeks post partum-an intra- and inter-rater study.

Aim: To evaluate intra- and inter-rater reliability when diagnosing major defects, and inter-rater reliability of diagnosing minor defects and muscle thickness of the pubovisceral muscle in primiparous women 6 weeks after vaginal delivery, using 3D/4D transperineal ultrasound.

Methods: Forty primiparous women were assessed using 3D/4D transperineal ultrasound. Volumes were acquired at maximal pelvic floor muscle (PFM) contraction, and diagnosis of muscle defects were done using tomographic ultrasound imaging (TUI) of the axial plane. Thickness was measured in three central levels of TUI. The stored volumes were analyzed offline by two investigators blinded to each others' results and the women's clinical data. Cohen's kappa (κ) and percentual agreement were calculated for defects, intraclass correlations coefficient (ICC) with 95% confidence intervals were calculated for thickness.

Results: Excellent intra-rater values were found for all major defects. Inter-rater values for bilateral and right-sided defects were excellent, and good for left-sided. Agreement for minor defects was poor. Measuring thickness ICC of 0.72 was found for the left side and 0.48 for the right side, although up to half of the cases had to be excluded owing to poor demarcation of the muscle.

Conclusion: Tomographic ultrasound imaging of the axial plane using three central slices seems to be a reliable tool for detecting major pubovisceral muscle defects shortly after childbirth. Minor defects showed low reliability. Muscle thickness measurements showed moderate reliability, but too many cases had to be excluded for this to be a useful method for determining muscle thinning 6 weeks after delivery.