Presentation
Possible rectal prolapse.
Patient Data
MRI proctogram
Structural findings:
Normal appearances of the pelvic viscera. No lymphadenopathy. Normal and symmetric appearances of the levator muscle complex.
Dynamic findings:
Measurements obtained using the PCL system at maximal straining are as follows:
Bladder neck: 13 mm below line (mild cystocele)
Cervix: 18 mm below line (mild uterovaginal prolapse)
Anorectal junction: 57 mm below line (mild anorectal junction descent)
Rectocele: 41 mm in depth (large sized anterior rectocele)
At the onset of evacuation, there is global pelvic floor descent, predominantly involving the posterior compartment. There is immediate formation of a moderate sized anterior rectocele which has a prominent perineal component. The anorectal angle opens appropriately and there is slow expulsion of the gel. The external prolapse predominantly involves the posterior wall where the low rectal wall intussuscepts out through the anal canal.
In summary:
No structural abnormality.
Global pelvic floor descent during evacuation - predominantly involving the posterior compartment.
Full-thickness external rectal prolapse involving the posterior low rectal wall.
Large anterior rectocele with some trapping of gel within it.
Mild descent of the bladder neck and uterine cervix during evacuation.
Case Discussion
Imaging plays a role when a patient has symptoms of an intermittent rectal prolapse that can't be reproduced in clinic on examination. Prolapses are shown to a greater degree on dynamic imaging that requires evacuation - the pressures on the pelvic floor in this context are more akin to real life activity, whereas the straining techniques used in clinic apply less pressure to the pelvis and therefore underestimate the size of prolapses.