The role of MRI pelvimetry in predicting technical difficulty and outcomes of open and minimally invasive total mesorectal excision: a systematic review

Background The difficulty of performing total mesorectal excision (TME) for rectal cancer partly relies on the surgeon's subjective assessment of the individual patient's pelvic anatomy and tumour characteristics, which generally influences the choice of platform used (open, laparoscopic, robotic or trans-anal surgery). Recent studies have found associations between several anatomical pelvic measurements and surgical difficulty. The aim of this study was to systematically review existing data reporting the use of magnetic resonance imaging (MRI)-based pelvic measurements to predict technical difficulty and outcomes of TME, and determine whether pelvimetry could optimise patient-specific selection of a particular surgical approach. Methods MEDLINE, Embase and Cochrane Library databases were systematically searched for studies reporting MRI-based pelvic measurements in patients undergoing surgery for rectal cancer, and the effect of these measurements on surgical difficulty. Results Eleven studies reporting the association between MRI-pelvimetry measurements and rectal cancer surgical outcomes were included. Indicators for surgical difficulty used in the included studies were involved circumferential resection margin, longer operative time, incomplete TME, higher blood loss, anastomotic leak, conversion to open surgery and overall complications. Bony pelvic measurements which were associated with increased surgical difficulty in more than one study were a smaller interspinous distance, a smaller intertubercle distance, a smaller pelvic inlet and larger pubic tubercle height. Two studies identified larger mesorectal fat area as a predictor of surgical difficulty. Conclusions Bony pelvic measurements may predict surgical difficulty during TME, however, use of different indicators of difficulty limit comparison between studies. Early data suggest MRI soft tissue measurements may predict surgical difficulty and warrants further investigation.