Study on the Effects of Potential Affecting Factors on the Midurethral Volume by High-Frequency 3-Dimensional Transvaginal Ultrasound

Objectives: The anatomic integrity of the female mid urethra is an important factor for urinary continence. However, the associations between the urethral volume and potential affecting factors still remain uncertain. The aim of this study was to investigate the impact of potential factors, including age, height, weight, body mass index (BMI), parity number, delivery mode, and menopause, on the midurethral volume to assist in more-accurate evaluations of urethral anatomy and urinary continence mechanisms in clinical practice.

Methods: A total of 244 women were included in this study. All patients had no incontinence symptoms and underwent transvaginal ultrasound examinations. Detailed histories and demographic data were collected. Urethral volumes were acquired, and volume parameters were measured offline, including the urethral sphincter volume (USV), midurethral complex volume (CV), and inner core volume (ICV). Correlations were analyzed by the Spearman test. For categorical variables, an analysis of variance, Mann-Whitney tests, or Kruskal-Wallis tests were used to estimate associations of potential affecting factors and volumes.

Results: The mean age, height, weight, and BMI ± SD of the patients were 35.42 ± 9.88 years, 161.50 ± 4.96 cm, 60.72 ± 11.42 kg, and 23.29 ± 4.20 kg/m² , respectively. Among potential affecting factors, age had a weak correlation with the USV, CV, and ICV (P = .031, .003, and .004; r = 0.140, 0.193, and 0.187), whereas parity numbers significantly affected the USV, CV, and ICV (P = .014, .021, and .026). The urethral volume became larger with increasing parity. Height (P = .391, .637, and .647), weight (P = .077, .130, and .245), BMI (P = .583, .592, and .643), delivery mode (P = .483, .171, and .104), and menopausal status (P = .611, .717, and .830) had no significant impact on the midurethral volume data (USV, CV, and ICV).

Conclusions: The midurethral volume tended to increase with age and parity in continent women.