Correlation between pelvic floor ultrasound parameters and vaginal pressures in nulliparous women: a subanalysis of the SUM-AN study

Introduction and hypothesis Pelvic floor ultrasound is used as a validated technique for measuring levator ani dimensions. Vaginal manometry has been used in the past as a method to assess levator ani muscle (LAM) strength. Whether the combination of both methods can contribute to our understanding of pelvic floor pathophysiology has not yet been described. We hypothesized that as female pelvic floor muscular hiatus increases, the vaginal pressure and strength decrease. Methods We recruited 20 asymptomatic nulliparous women ages 18-85 years. Minimal levator hiatus (MLH) area, anteroposterior/left-right (AP/LR) diameter ratio, the distance between levator plate and the pubic symphysis (LP-PS) while at rest and squeeze were measured using endovaginal ultrasound (US). Vaginal pressure at rest, squeeze (Kegel) and Valsalva were measured using 3D manometry. Logistic and linear regression analysis was performed to assess correlations. Results MLH area was negatively correlated with the sum of all the squeeze pressures produced on the four walls of the vagina (p = 0.049, R-2 = 0.197). There was also a borderline negative correlation between MLH and the sum of rest pressures (p = 0.09, R-2 = 0.15). AP/LR ratio was negatively correlated with the sum of squeeze pressures (p = 0.056, R-2 = 0.197). LP-PS distances, both while at rest and during squeeze, were negatively correlated with the vaginal squeeze pressure (p = 0.046, R-2 = 0.21; p = 0.011, R-2 = 0.31, respectively). LP-V distance, both at rest and during squeeze, was negatively correlated with the sum of squeeze pressures on four vaginal walls (p = 0.02, R-2 = 0.25; p = 0.005, R-2 = 0.36, respectively). Conclusions Stronger levator ani muscles, smaller MLH area and a more oval shape of pelvic floor hiatus as assessed by pelvic floor ultrasound are associated with higher squeeze vaginal pressures as assessed by 3D manometry.