Introduction Bony pelvimetry varies between the sexes and has been found to be a possible factor in predicting operating time, quality of histological total mesorectal excision (TME) grade and positivity of circumferential resection margin (CRM) after rectal cancer surgery. Low pelvic dissection is anecdotally more difficult in narrow and deep pelves.

This observational study aimed to identify any relationship between magnetic resonance (MR) bony pelvimetry measurements and operative or oncological outcome in patients undergoing rectal cancer surgery.

Method A prospective database of patients undergoing anterior resection was maintained including demographics, operating time, tumour characteristics and oncological outcomes. MR pelvimetry recordings were performed by a surgeon ‘blinded’ to outcome. Chosen endpoints were local recurrence (LR), disease free survival (DFS), overall survival (OS) and operating time (OT). Binary logistic regression and Pearson’s correlation coefficient were performed for statistical analysis.

Results A total of 171 patients underwent surgery (58 abdomino-perineal resection, 113 anterior resection) between 01/2009 and 05/2014. Median operating time was 318 min (range 91–421). Median follow-up was 25 months. There were 10(5.8%) patients with positive CRM, 10(5.8%) patients with LR, and 28(16.3%) deaths during follow-up period. There was no significant correlation between individual MR pelvimetry measurements and LR, DFS, OS or OT. However, the distance between the tip of the coccyx to the sacral promentory, and the tip of the coccyx to the body of S3 were strongly correlated with operating time, with the former also being closest to significance in correlation with LR.

Conclusion Our study does not demonstrate any statistically significant relationship between bony pelvimetry and outcome after low rectal cancer surgery. A deep pelvis is correlated non-significantly with local recurrence and prolonged operating time. Further follow-up is required for complete five year oncological data.

Disclosure of interest None Declared.