Urethral deviation may be a potential pathogenic factor in female stress urinary incontinence: a cross-sectional study

Background: Stress Urinary Incontinence (SUI) is one of the top five chronic diseases globally. The traditional theory of SUI does not adequately explain certain subgroups of patients. This study aims to investigate the risk factors and potential mechanisms underlying female SUI. Materials and Methods: A dual-tertiary center, cross-sectional study was conducted. A finite element model (FEM) was developed using data from a female volunteer. A total of 42 rats were utilized as animal models. Female participants presenting with lower urinary tract symptoms were recruited and categorized into four groups based on their SUI and Levator ani avulsion (LAA) status: SUI +/LAA +, SUI +/LAA–, SUI–/LAA +, and SUI–/LAA–. Data were collected from the FEM, animal models, and human participants. Results: The FEM demonstrated that in simulations of unilateral LAA, the ipsilateral urethra exhibited deviation and displacement toward the site of avulsion, accompanied by distortion. Rats with LAA showed a significantly higher incidence of SUI (P = 0.031), particularly those with unilateral LAA (P = 0.011). A total of 1629 women were ultimately included in the study. Statistical significance was observed specifically in patients with unilateral LAA (OR = 1.87 (95% CI,1.389–2.481), P < 0.001). Measurements of the levator-urethral gap (LUG) indicated that the closer the avulsion site was to the urethral opening, the higher the likelihood of SUI occurrence, which aligns with the urethral deviation patterns observed in the FEM analysis. Conclusion: Unilateral LAA is a significant risk factor for SUI. The urethral deviation induced by unilateral LAA may represent an additional etiological mechanism of SUI, beyond the traditional fascial hammock theory.