The rectosigmoid problem

The lack of consensus over the transition point for the end of the sigmoid and beginning of the rectum is a problem for the colorectal multidisciplinary team. In this review, we survey the wide number of landmarks for the rectosigmoid junction, and describe the theoretical and evidence-based strengths and weaknesses of each one. Without a reliable definition of the rectum, sigmoid and rectal cancers will be classified inconsistently. As the treatment strategies for sigmoid and rectal cancers are radically different, incorrect tumour localisation has a substantial impact on patient management, leading to under or over treatment. Inconsistent classification will confound investigation of metastatic patterns and treatment outcomes. Now that the rectosigmoid junction has been recognised as a distinct segment of colon by the International Classification of Diseases, further heterogeneity in management and outcomes could result to the detriment of patients and research. We describe a bespoke, anatomical and reliable landmark for the rectosigmoid junction; the sigmoid take-off. •A consistent, standardised definition of the rectum is required.•Current bony and metric landmarks will mis-classify sigmoid and rectal tumours.•The sigmoid take-off is an anatomical imaging landmark that defines the rectum.•Further research is required to confirm the validity and reliability of the sigmoid take-off.