To explore the clinical value and advantages of transrectal biplanar high-frequency ultrasound in imaging vaginal structure.

From January to March 2021, a ultrasound physician used biplane high-frequency ultrasound to transrectally image the vagina of 103 normal women from the Ultrasound Center of Shenzhen Luohu People's Hospital, of which 53 were reproductive women and 50 were postmenopausal women. The sagittal section of the middle and lower vagina was imaged by the linear array high-frequency ultrasound with a biplane probe, and the transverse section of the lower vagina was imaged by the convex array high-frequency ultrasound, and the images were saved in the ultrasound system. Then, two ultrasound physicians measured the vaginal wall thickness at the level of the internal urethra of the bladder triangle in the sagittal section of the vagina. One of the ultrasound physicians repeated the measurement once a week later. The independent sample t test was used to compare the difference of vaginal wall thickness between the two groups, and the repeatability and consistency were assessed by intra-group correlation coefficient (ICC) and Bland-Altman diagram.

The vagina located between the anterior wall of the rectum and the posterior wall of the bladder and urethra showed "three lines and two zones" on the sagittal section. The "three lines" were the hyperechoic fibrous membrane of the outer wall of the anterior and posterior wall of the vagina and the mucosal layer of the anterior and posterior wall closed together in the middle. The "two zones" were the hypoechoic muscle layer of the anterior and posterior wall of the vagina. In the transverse section, the vaginal muscular layer showed an "inverted trapezoid" sign of low echo, which was the anterior and posterior wall of the vagina and the lateral wall of the vagina, respectively. The vaginal mucosa layer showed a hyperechoic "H" shape. The thickness of the vaginal wall measured by the two ultrasound physicians was (10.43±3.02) mm and (10.78±3.06) mm in reproductive women, and (9.05±2.22) mm and (9.15±2.28) mm in postmenopausal women, respectively; the difference was statistically significant (t=2.651, P=0.048; t=3.077, P=0.024). The measurement of vaginal wall thickness in reproductive women had excellent reproducibility (ICC=0.98) and consistency (ICC=0.97). Vaginal wall thickness measurements in postmenopausal women also had excellent reproducibility (ICC=0.96) and consistency (ICC=0.95).

The measurement of vaginal wall thickness by transrectal biplanar high-frequency ultrasound has good repeatability and consistency, and it can be used to evaluate vaginal morphology in sagittal and transverse sections, which is an accurate and efficient imaging method to evaluate the middle and lower segments of the vagina.