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 (Pdelta) (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.