Three‐dimensional endoanal ultrasound measurements for the assessment of perineal body size in a cohort of Swedish nulligravidae

Abstract Introduction Despite the perineal body's important functional role, few studies have specifically evaluated its size in women. Existing three‐dimensional ultrasound studies typically involve small samples, often including both nulliparous and parous women, and focus on measuring internal and external sphincter thickness rather than the perineal body itself. Material and Methods This cross‐sectional study primarily aimed to measure the size of the perineal body in a population of nulligravidae ( n = 148) using three‐dimensional endoanal ultrasonography. Secondary aims were to (1) evaluate the feasibility and reproducibility of 3D ultrasound interpretation across raters with varying levels of experience and (2) investigate how perineal body measurements correlated with body composition. Results The study participants had a mean age of 31 years (SD ± 6), a mean height of 167 cm (SD ± 5.9), and a mean body mass index (BMI) of 25.3 kg/m 2 (SD ± 5.6). The perineal body had a mean proximal–distal length of 17.5 mm (SD ± 3.0), with excellent interrater reliability (ICC = 0.89; 95% CI: 0.85–0.92). The mean antero–posterior height was 9.7 mm (SD ± 1.4; ICC = 0.67, 95% CI: 0.57–0.75), and the mean perineal body area was 120 mm 2 (SD ± 28; ICC = 0.84, 95% CI: 0.77–0.88). Results suggest that perineal body measurements obtained through standardized 3D endoanal ultrasonography are reproducible across raters, supporting the method's feasibility regardless of prior ultrasound experience. BMI and weight showed a moderate positive correlation with both the length and the area of the perineal body ( p = 0.05). Conclusions Standardized 3D endoanal ultrasonography provides reproducible measurements of the perineal body in nulligravid women and measurements correlated moderately with body composition. This suggests the use of this imaging method in asymptomatic populations and future research on pelvic floor function.