Figure 2. Representative examples of normal and abnormal anorectal evacuation recorded with MRI (upper panel) and high resolution manometry (lower panel).

With MRI, observe increased puborectalis indentation during squeeze (arrow, panel B) and normal relaxation of the puborectalis, perineal descent, opening of the anal canal and evacuation of ultrasound gel during evacuation (panel C). During evacuation in constipated patients, observe paradoxical contraction of the puborectalis (panel D) and exaggerated perineal descent with an enterocele (panel E). High resolution manometry shows increased anal pressure during squeeze (G) compared to rest (F). The white rectangle demarcates the duration of squeeze (G) and evacuation (H-K). Observe increased rectal pressure with anal relaxation during evacuation (H) in a healthy person. By contrast, during evacuation in constipated patients, observe increased rectal pressure with paradoxical anal contraction (I), no change in rectal pressure versus rest (J), and no change in rectal pressure with paradoxical anal contraction (K).