MR Defecography in Assessing Functional Defecation Disorder: Diagnostic Value of the Defecation Phase in Detection of Dyssynergic Defecation and Pelvic Floor Prolapse in Females

Objective: Dyssynergic defecation (DD) and pelvic floor prolapse often coexist in female functional defecation disorder. A retrospective study was performed to evaluate the ability of dynamic MR sequences with the straining and defecation phase to detect paradoxical puborectalis contraction and occult multiple-compartments disorders. Methods: Fifty-three females clinically diagnosed with DD underwent magnetic resonance defecography. The dynamic sequences consist of rest, squeeze, straining, and defecation. The straining phase (pre rectal filling) and defecation phase (post rectal filling) were acquired to assess for pelvic floor relaxation and pelvic organ descent. MR images were analyzed by 2 radiologists with regard to paradoxical puborectalis contraction (changes in the anorectal angle [ARA]) and the presence of pelvic organ prolapse in straining phase and defecation phase independently. Statistical analysis was performed using Wilcoxon’s matched-pairs signed-ranks test and Crosstabs test for matched pairs. Results: Among the 53 patients with DD, 24 individuals (45.3%) were diagnosed DD with multifocal disorders. Comparison between the straining and the defecation phase revealed that there was no significant difference in the change of the ARA (p > 0.05), while significant differences were found in cystocele, vaginal or cervical prolapse, rectocele and descending perineum syndrome between the straining and the defecation phase (p < 0.05). The defecation phase with impaired evacuation distinguished additional anterior/middle compartments findings in female DD patients. Conclusion: The straining phase and the defecation phase have the same ability in assessing paradoxical puborectalis contraction of the DD. Compared with the straining phase, the defecation phase provides the maximum stress to the pelvic floor resulting in complete levator ani relaxation. In addition to diagnosing the abnormal anorectal function, the defecation phase with the discharge of the rectal filling demonstrates maximum anterior/middle pelvic organ descent in DD patients.