Dyssynergia phenotypes in obstructed defecation: insights from Fecobionics assessment

OBJECTIVE: Obstructed defecation syndrome (ODS) is a chronic constipation subtype. Conventional tests are limited by non-physiological conditions and poor correlation with symptoms. This study investigated anorectal dynamics and dyssynergia phenotypes in patients with ODS using Fecobionics. METHODS: This study was designed as a prospective observational study including 10 control subjects and 25 patients with ODS. All measurements were performed according to a predefined protocol. All patients with ODS underwent clinical evaluation, anorectal manometry (ARM) and defecography. Fecobionics recorded anorectal pressures, sensation and expulsion performance. Expulsion dynamics were further analysed using preload-afterload diagrams to characterise dyssynergia subtypes. RESULTS: Compared with the control group, the ODS group showed prolonged expulsion time (76 (23-120) vs 18.7 s (10.6-34), p<0.01), reduced effective propulsive force (P_delta) (26.2 (8.6-35.9) vs. 48.2 cmH₂O (32.5-88.0), p<0.01), increased number of contractions (7 (4-14) vs 2.5 (1.3-3.8), p<0.01) and higher paradoxical contraction rates (71% (50-100) vs 0% (0-44), p<0.01). ARM during attempted evacuation (push) demonstrated lower anal relaxation rates in the ODS group (16% (12-37) vs 36% (27-44), p<0.03). Correlation analyses demonstrated that impaired Fecobionics metrics were associated with greater symptom burden. Three dyssynergia phenotypes were identified: multiple simultaneous contractions, insufficient or delayed anal relaxation and persistently elevated outlet pressure. CONCLUSION: Fecobionics enables integrated and physiologically relevant assessment of anorectal function and identifies distinct dyssynergia phenotypes in ODS, reflecting heterogeneous mechanisms of outlet obstruction with implications for individualised management. STUDY REGISTRATION: ChiCTR2300078807.