The Influence of Age, BMI, and Parity on 3D MRI-Derived Morphology of Pelvic Floor Muscle and Levator Ani Hiatus in Women With Stress Urinary Incontinence

Objective

To measure the morphology of the pelvic floor muscle and levator ani hiatus (LAH) using 3D MRI segmentation in females with (SUI) and to assess correlations with age, body mass index (BMI), and parity.

Methods

This study includes 80 patients with SUI who underwent 3.0 T pelvic MRI. Patients were grouped based on age, BMI, and parity. Manual segmentation and 3D modeling of the pelvic floor muscle and LAH were performed to get volumetric and dimensional measurements. Statistical analysis included Kruskal–Wallis, Mann-Witney, and post hoc testing to evaluate group variations.

Results

The cohort included patients from 20 to 90 years old (mean 53.9 ± 11.7), with a mean BMI of 25.3 ± 3.4 and a mean parity of 1.85 ± 1.03. Significant variations in LAM surface (H(2) = 6.650, p = 0.036), flatness (H(2) = 6.471, p = 0.039), median intensity (H(2) = 8.218, p = 0.016), and curvature mean (H(2) = 7.382, p = 0.025) among age groups. The greatest LAM surface rankings were found in the 50–65 age range, whereas the highest LAM flatness ranks were found in those over 65 years old. BMI demonstrated a limited association, with overweight/obese participants exhibiting 11.3% larger LAM surface area compared to normal/underweight individuals (p = 0.044, r = 0.225). No significant associations were found between parity and any pelvic floor morphometric parameters (all p > 0.05).

Conclusion

This study identifies age-dependent morphological changes in levator ani muscle architecture as the primary determinant of pelvic floor structural adaptation in women with stress urinary incontinence. These quantitative shape-based parameters offer novel diagnostic and therapeutic insights, advancing precision medicine approaches in urogynecological assessment and management.