Intrarectal and rectoanal intussusception represent the initial phases of a rectal prolapse when a fold develops in the rectal wall during pushing, prolapsing into the rectum; subsequently, the
intussusception descends to obstruct the anal canal and finally becomes an external prolapse. When a defecography is being done, internal intussusception can be difficult to diagnose. Firstly,
prolapse of anal cushions and variations of fold patterns due to some degree of asymmetry of the rectum during its emptying may lead to misinterpretation. Secondly, as seen in rectoceles,
intussusception can represent a mere defecographic finding or the cause of an obstructed defecation. Criteria of their clinical importance include the presence of transverse or oblique infolding of
more than a 3 mm thickness formed by invagination of the rectal wall causing an obstruction to rectal evacuation. These findings must be interpreted in the light of the patient's clinical history.
More advanced degrees of intussusception may cause rectal pain or even lead to solitary rectal ulcer syndrome leading to the elimination of blood or mucus through the rectum.