Background: To demonstrate the pelvic peritoneal recesses during voiding, evacuation proctography was combined with positive contrast peritoneography. Methods: In 30 constipated patients, peritoneography was performed, followed by proctography, Results: During evacuation rectogenital. herniation developed in 20 patients (66%), without visceral filling in 12 (40%). Conclusions: Posterior pelvic floor hernia is common during defecation, Less than half fill with bowel and many may not be apparent on standard proctography.