Type:
Educational Exhibit
Keywords:
Cancer, Diagnostic procedure, MR, Pelvis, Oncology, Gastrointestinal tract
Authors:
R. M. Antunes, P. G. M. G. Ferreira; Lisbon/PT
DOI:
10.1594/ecr2018/C-3146
Background
The rectum extents about 15cm proximally from the anal margin.
Tumor arising in this section of the gastrointestinal tract are divided,
according to the distance of their inferior border to the anal margin,
into upper,
middle and lower third tumors.
Low rectal tumors (LRT) arise within 5cm from the anal margin.
The standard of care for rectal tumors is total mesorectal excision with tumor-negative margins.
As opposed to tumors on the upper two thirds,
LRT are associated with higher rates of positive resection margins,
higher local recurrence rates and poorer survival.
This is mainly due to anatomic considerations,
namely the close proximity to the mesorectal fascia,
which tapers distally,
and to the anal sphincter complex [1,
2].
MRI is used in the preoperative staging of rectal tumors to evaluate for surgical margin invasion and identify the patients that could benefit from chemoradiation (CRT) prior to surgery.
When assessing LRT,
careful attention should be given to the levator ani muscle,
sphincter complex,
and intersphincteric space.