Elevated puborectalis stiffness measured by endovaginal shear wave elastography is associated with obstructed defecation syndrome

Abstract

Abstract Obstructed defecation syndrome (ODS) is a common functional disorder in which conventional B-mode ultrasound demonstrates abnormal puborectalis muscle (PRM) behaviour but cannot quantify intrinsic tissue mechanical properties. Shear wave elastography (SWE) provides a quantitative imaging surrogate of local tissue stiffness. To compare PRM stiffness measured by endovaginal SWE among women with ODS, women with functional constipation (FC) and an asymptomatic comparator group (ACG), and to examine the relationship between PRM stiffness and levator plate descent angle (LPDA), anorectal angle (ARA), levator contraction metrics and levator avulsion. Prospective, cross-sectional, exploratory discrimination study. Participants underwent B-mode transperineal ultrasound (TPUS) for measurement of LPDA, ARA, percentage of levator contraction, levator avulsion and multicompartmental prolapse, and endovaginal ultrasound (EVUS) with SWE for evaluation of PRM stiffness at five predefined anatomical zones. The system acquired shear wave velocity (Cs, m/s) as the primary physical measurement; Young’s modulus (E, kPa) was derived as E = 3ρCs² and is the quantity reported throughout. Intraclass correlation coefficients (ICC) quantified consistency across the five predefined zones; Kruskal-Wallis tests with Dunn-Bonferroni post-hoc comparisons compared groups; effect sizes are reported as Hedges’ g with 95% confidence intervals (CI); receiver-operating characteristic (ROC) curves assessed discrimination; and binary logistic regression adjusted for functional and demographic covariates examined associations with ODS group membership. A total of 124 women were assessed (ODS = 62; FC = 16; ACG = 46). Consistency across the five sampled zones was high (ICC 0.870 [95% CI, 0.83–0.90]). Puborectalis stiffness was higher in ODS than in ACG ( P < 0.001, Hedges’ g 0.75) and than in FC ( P = 0.010, Hedges’ g 0.71 [95% CI, 0.15–1.27]). No statistically significant difference was detected between FC and ACG in any zone (all P ≥ 0.236). For discrimination of ODS from ACG, Zone 4 yielded the numerically highest area under the curve (AUC 0.749 [95% CI, 0.658–0.840]) and the global mean an AUC of 0.746 (95% CI, 0.655–0.837) at an exploratory cohort-derived cutoff of 23.5 kPa (sensitivity 62.9%, specificity 80.4%); these AUC values were not formally compared. For discrimination of ODS from FC, the global mean AUC was 0.715 (95% CI, 0.587–0.843). LPDA during contraction was lower in ODS than in ACG (32.2° ± 13.4° vs. 40.2° ± 14.6°; P = 0.003). After adjustment for age, menopausal status, previous pelvic surgery and pelvic floor functional parameters, global mean stiffness remained associated with ODS group membership after adjustment for the covariates included in the model (odds ratio 1.09 per 1 kPa increase [95% CI, 1.02–1.16]; P = 0.009; equivalent to an odds ratio of 2.06 per 1-SD increase); levator avulsion, multicompartmental prolapse and bladder outlet obstruction could not be entered owing to complete separation. Endovaginal SWE detected elevated PRM stiffness in women with ODS that was not detected in FC. The technique represents a potential quantitative adjunct to conventional TPUS in the assessment of evacuatory disorders and should not at present be used to establish a diagnosis or to select patients for treatment. External validation against an independent physiological reference standard is required before clinical application.

The authors' abstract, as published at the source. Scientific Reports, 2026 · DOI ↗