Accurate Differentiation of Dyssynergic Defecation Patients from Normal Subjects Based on Abnormal Anorectal Angle in MR Defecography



We aimed to study the kinematic indices of the pelvic floor, anorectal angle and the descent of
perinea, and the differing movement, in dyssynergic defecation patients in comparison with healthy controls, based
on MR defecography.


Twenty-two individuals involved with dyssynergic defecation constipation and fourteen healthy
asymptomatic subjects fell into this study. In four dynamic pelvic floor MRI indices, namely paradox (unusual change
of anorectal angle), perineal descent during straining, perineal ascent, and narrowing of anorectal angle at squeeze,
were measured in patients and healthy subjects.


Paradox Index had the highest sensitivity (95.45%) and specificity (92.86%) for detection of dyssynergic
defecation, with an R2
value of near 1 (0.902). The sensitivity and specificity of other indices were not high; therefore,
no significant improvement could be achieved using other indices along with Paradox Index. Negative Predictive
Value (92.85%) and Positive Predictive Value (95.45%) were only high in Paradox Index.


Paradox Index was indicated to be the best finding of MR defecography for identifying dyssynergic
defecation patients from healthy controls. Hence, MR defecography could be exploited as an authentic tool to
manifest the patients the paradoxical function and the relevant muscles of pelvic floor, which could enhance their
imagination of the correct defecation pattern during their treatment.