Magnetic Resonance Defecography Criteria for the Diagnosis of Dyssynergic Defecation

: Evidence regarding the diagnostic value of MR defecography (MRD) for confirming dyssynergic defecation (DD) is limited. We aim to evaluate the diagnostic performance of MRD parameters in identifying patients with DD.

: This retrospective study was conducted at a university hospital. Data from 235 consecutive adult patients with chronic primary constipation who underwent high-resolution anorectal manometry (HR-ARM), balloon expulsion test, and MRD between 2020 and 2024 were analyzed. The diagnostic performance of each dynamic MRD parameter was assessed using HR-ARM combined with balloon expulsion test as the reference standard.

: A total of 109 participants (86 females; mean age 53.1 ± 15.3 years) were included, of whom 70 patients (64.2%) were diagnosed with DD. Quantitative dynamic MRD parameters, including the M-line, anorectal angle (ARA), and anal canal width (ACW), demonstrated significantly good discriminatory ability for differentiating patients with DD (all P < 0.05). At cutoff values of 2.0 cm for the M-line at defecation combined with prominent puborectalis muscle or abnormal evacuation of contrast during defecation, 1.6 cm for M-line change, 114° for ARA at defecation, -5° for ARA change, and 10 mm for ACW during defecation, these parameters demonstrated acceptable diagnostic performance, achieving optimal specificities (82.1% to 92.3%), positive likelihood ratios (3.66 to 7.06), and diagnostic odds ratios (8.25 to 14.25). Multivariate analysis identified ARA and ACW at defecation as independent diagnostic predictors of DD (P < 0.05).

: These findings support the establishment of practical and reliable MR defecography-based diagnostic criteria for patients with dyssynergic defecation.