Effect of Squeeze, Cough, and Strain on Dynamic Urethral Function in Nulligravid Asymptomatic Women: A Cross-Sectional Cohort Study

Importance In the past, urethral shape, mobility, and urodynamics have been used to retrospectively demonstrate correlations with stress urinary incontinence. Our previous work has shown a relationship between urethral function and shape in symptomatic women. Objective This study aimed to characterize the effect of pelvic floor squeeze and strain maneuvers on urethral shapes and pressure in a cohort of patients without pelvic floor disorders. Study Design In this cross-sectional study, volunteers underwent dynamic pelvic floor ultrasound examination, and a modified urodynamic study. Urethral length, thickness, and proximal and distal swing angles were measured at rest, squeeze, and strain. The midsagittal urethral walls were traced so that a statistical shape model could be performed. Means and standard deviations of imaging and urodynamic measures were calculated. Results Data from 19 participants were analyzed. On average during squeeze compared with rest, urethral length increased by 6%, thickness decreased by 42% (distal, P < 0.001), 10% (middle), and urethral pressure increased by 14%. Opposite shape changes—length decreased by 10% (P = 0.001), thickness increased by 57% (distal, P < 0.001), 20% (middle, P < 0.001)—and increased urethral mobility were observed during strain, with larger pressure increases occurring (29%, P < 0.001). Fifty-one percent of the total shape variance described the differences between maneuvers. These differences were statistically different between groups (P < 0.001 for comparisons, all others P > 0.05). Conclusions Dynamic ultrasound and urodynamics allow for the establishment of baseline ranges in urethral metrics (2-dimensional measures, shape, and pressure) and how they are altered during maneuvers. These data can allow for a more objective identification of incontinence via ultrasound and urodynamic testing.