Internally Peer Reviewed Defecation is a complex action requiring coordination and sequential activation of a large number of muscles. It is controlled by the autonomic nervous system, but is also under voluntary control.
Defecation is initiated by distension of the rectum by feces arriving from the sigmoid colon.
This sensation leads to a chain of events which ends in expulsion of feces from the anus. The act of defecation is voluntarily controlled in healthy, normally functioning people. Defecography Defecography, or evacuation proctography, is a radiologic study which produces an anatomic depiction of the changes that occur in the rectum and anal canal during defecation. It also provides information about the movement of the pelvic floor, such as movement of the puborectalis sling during evacuation, squeezing and rest. Defecography is a technique in which a barium contrast medium is introduced into the rectum.