Repeatability of Junctional Zone Measurements Using 3-Dimensional Transvaginal Sonography in Healthy Fertile Women

To describe the junctional zone and determine the intraobserver and interobserver repeatability of junctional zone measurements using 3-dimensional (3D) transvaginal sonography in healthy fertile women.

We examined 82 consecutive women with 3D transvaginal sonography. The maximum and minimum junctional zone thickness was measured in all uterine walls. The difference between maximum and minimum thickness and average measurements (maximum thickness + minimum thickness/2) of the anterior, posterior, fundal, and lateral walls were calculated. Among the first 40 consecutive women, intraobserver and interobserver repeatability was evaluated according to the Bland-Altman method and expressed as a coefficient of repeatability.

Using 3D transvaginal sonography, we visualized a thin and regular junctional zone in most women. The posterior uterine wall had the largest median maximum junctional zone thickness value of 5.2 (interquartile range, 3.8-6.5) mm. Ten women (12%) had maximum thickness values of 8.0 to 12.0 mm. The maximum thickness in each uterine wall had intraobserver and interobserver coefficients of repeatability of ±2.1 to ±3.4 and ±2.6 to ±3.9 mm, respectively, which were reduced by average measurements: ±1.9 and ±2.0 mm (anterior and posterior walls) and ±1.5 mm (fundal and lateral walls) for intraobserver and interobserver values. Correlations between measurements were poor in the narrow range of junctional zone thickness.

The junctional zone has an indistinct outline on 3D transvaginal sonography, resulting in measurement errors within a broad range of ±2 to ±4 mm, which were only reduced to some extent by average measurements. The thickness of the junctional zone varied within a narrow range in this healthy fertile population, and reliability measurements of junctional zone thickness have to be evaluated in women with a wider range of thickness. The observer repeatability and reliability of junctional zone measurements need to be further evaluated and refined before applying this method in clinical practice.