Standardization of techniques for measuring the urethral inclination angle during transperineal ultrasound: choosing the anatomical reference points

Objective. Search for an optimal ultrasound examination technique that allows for increased accuracy in assessing the angle of urethral inclination, taking into account fixed anatomical landmarks. Material and methods. The study included 30 women of reproductive age without signs of stress urinary incontinence and pelvic organ prolapse. The angle of urethral inclination was assessed using transperineal ultrasound in three body positions: lying on the back on a horizontal plane, in the lithotomy position, and lying on the back with a cushion under the lower back. Two methods of measuring urethral rotation were compared: the first was an assessment relative to the vertical axis passing through the neck of the bladder; the second was an assessment relative to the longitudinal axis of the pubic symphysis. Results. The first technique demonstrated high variability when changing the patient’s body position — in the supine position on the median plane, the urethral inclination angle was 14º [8; 17]º, in the lithotomy position — 20º [16; 25]º, in the supine position with lumbar support on a bolster — 10º [7; 12]º. When assessing the dynamic change in this angle depending on the body position, statistically significant differences were noted (Friedman ANOVA method: χ2=37.83; p=0.001). At the same time, when using the second technique, more stable results were determined, less dependent on the pelvic inclination angle. In the supine position on the plane, the urethral inclination angle was 70º [57; 79]º, in the lithotomy position — 72º [67; 86]º, in the supine position with lumbar support on a bolster — 69º [58; 80]º. At the same time, urethral mobility depending on the patient’s body position when using the second technique also had statistically significant deviations (χ2=18.79; p=0.02), but these fluctuations were less pronounced. Thus, when changing the body position from the supine position on a plane to the lithotomy position when using the first technique, the angle of inclination of the urethra increased by 42.8% (1.4 times), while when using the second technique, the fluctuations were minimal — by 2.8%. Conclusion. Measuring the angle of urethral inclination relative to the longitudinal axis of the pubic symphysis minimizes the influence of the patient’s body position and anatomical features on the results obtained. This transperineal ultrasound technique helps to increase the accuracy of detecting stress urinary incontinence and can become a standard for diagnosing urethral mobility in women.