CT/MRI pelvimetry as a useful tool when selecting patients with rectal cancer for transanal total mesorectal excision

The quality of a total mesorectal excision (TME) is one of the most important prognostic factors for local recurrence of rectal carcinoma. The aim of this study was to clarify the manner in which lesser pelvis dimensions affect the quality of TME via the transabdominal approach, while simultaneously defining the criteria for selecting patients most likely to have Grade 3 TME outcomes for a transanal approach using the TaTME technique.

An analysis from the registry was conducted using 93 of total 198 patients with rectal cancer of the mid- and lower third of the rectum who underwent: (1) a low anterior resection, (2) an ultra-low resection with coloanal anastomosis, or (3) an intersphincteric rectal resection, all with total mesorectal excision. The procedures were carried out at the Department of Surgery at the University Hospital Hradec Králové between 2011 and 2014. Rectal specimens were histopathologically examined according to a standardized protocol. Pelvimetry data were obtained using anteroposterior, transverse, and sagittal CT or MRI scans.

A correlation was found between the quality of the TME and pelvimetry parameter A5, i.e., the angle between the longitudinal axis of the symphysis, and the lines between the symphysis and the promontory (R(2) = -0.327, p < 0.001). The ordinal regression method was used to identify parameters of the model describing levels of probability for TME quality. These relationships were described by equations that provide probability of the achievement of each grade of TME.

The correlation described by obtained equations between pelvimetry parameters and the quality of TME represents a new tool for use in preoperative decision-making with regard to resection via the transanal approach (TaTME).