BACKGROUND: Total mesorectal excision has evolved from open to minimally invasive techniques. To overcome difficulties in the lowest part of the pelvis, transanal total mesorectal excision was introduced and has gained acceptance in the recent years. The results of transanal total mesorectal excision seem to be comparable to laparoscopic total mesorectal excision. Whether or not transanal total mesorectal excision has changed the pattern of defects in the retrieved mesorectal specimens is yet to be clarified.

PURPOSE: To determine the pattern of mesorectal defects following transanal total mesorectal excision, compared to laparoscopic total mesorectal excision. The primary end-point was the location of defects in the part of the mesorectum below the peritoneal reflection, as it is this part, which is dissected from below in the transanal total mesorectal excision procedure.

METHODS: From our transanal total mesorectal excision database that includes all transanal total mesorectal excision procedures performed at our institution since 2013, we have included 29 patients who originally had defects in their retrieved specimens. Another 29 patients who underwent laparoscopic total mesorectal excision with mesorectal defects served as a control group. All specimen photos and pathology reports were reviewed systematically; sites and pattern of defects were defined.

RESULTS: A higher ratio of the defects in the laparoscopic total mesorectal excision group was located below the peritoneal reflection (P = 0.043). The distribution of defects by anatomical quadrant was not statistically different between the groups.

CONCLUSIONS: The ratio of defects below the peritoneal reflection was lower in the transanal total mesorectal excision group. Whether this is due to a lower incidence of defect in transanal total mesorectal excision is not part of our study.