Appropriate parameters to be measured during defecography have evolved over time, based on the contributions of numerous authors. Accordingly, consistent objective measures and their implications are not yet universally accepted due to a lack of uniform technique.3'5'17 However, the following definitions are generally considered standard based on their widespread use:
Anal canal length: The distance from the anal verge (defined by barium marking the skin or a marker placed on the perineum) to the rectum.
Anorectal angle: The angle between the axis of the anal canal and the posterior rectal wall (posterior anorectal angle) or the center of the rectum (central anorectal angle). Perineal descent: The vertical movement of the anorectal junction from its position at rest. Reference points are the ischial tuberosities5 or the pubococcygeal line drawn from the pubis to the tip of the coccyx.6
Peritoneocele: A caudal extension of the pouch of Douglas or rectouterine excavation to below the upper third of the vagina. A perito-neocele can contain fluid or omentum and is termed an enterocele when it contains bowel. Peritoneoceles can be further described as septal, vaginal, and rectal, based on anatomic features.10
Rectal intussusception: A descent of the entire thickness of the rectal wall, which can extend to the anal verge. When the rectal wall intus-suscepts inferiorly through the anus, the condition is termed rectal prolapse.18
Rectocele: A rectocele is defined as an out-pouching of the rectum that is more pronounced during straining and typically occurs anteriorly, although posterior rectoceles have also been described. More than 2 cm of outpouching may be considered abnormal.
Rectosacral gap: The horizontal distance between the posterior line of the rectum and the sacrum at S3.17
Rectovaginal space: The distance between contrast in the vaginal and contrast in the rectum.18
Sigmoidocele: Abnormal descent of a loop if sigmoid into the pelvis which may be first, second, or third degree (Fig. 9.2).19
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