Is the volume retained after defecation a valuable parameter at defecography ?

The intention of this study was to correlate the retained volume at the end of defecography to certain defecographic findings and to the sense of incomplete emptying. In 170 defecographic series, the retained barium was estimated planimetrically. No particular defecographic finding determined a higher or lower amount of remaining volume, and the sense of incomplete evacuation did not depend on the amount of retained volume. Thresholds of urge and perception on anorectal manometry did not differ between patients with and without the feeling of incomplete evacuation. A rectocele, isolated or combined with an internal prolapse, caused the retained volume to be in the lowermost part of the rectum, whereas, in the case of an isolated intussusception, the remaining volume was located in the middle or higher part of the rectum. It is concluded that defecographic findings do not in general explain incomplete emptying or the sense of incomplete emptying, but they may determine the localization of the retained volume.