Comparison of the sigmoid take-off with other definitions of the rectosigmoid junction: A retrospective comparative cohort analysis.

Abstract

The diversity in definitions for the rectosigmoid junction is becoming a major obstacle in standardizing optimal treatment of rectal cancers. The study aimed to determine the average distance of the sigmoid take-off from the anal verge and its association with individual factors. Patients diagnosed with rectal and sigmoid colon cancer in our centre from January 2010 to December 2018 were retrospectively enrolled in the cancer group. The results of 200 controls without colorectal disease were also reviewed (normal group). The distance of different landmarks and margins of cancer from the anal verge were retrieved from computed tomography (CT), magnetic resonance imaging (MRI), and endoscopy findings. The cancer group comprised 635 patients (381 men, median age: 64 years). The average distances of the sigmoid take-off from the anal verge measured in CT and MRI were comparable (P=0.483). On MRI, the average distance of the sigmoid take-off from the anal verge in the cancer group was comparable with that of the normal group (P=0.070). Multivariate regression revealed that the distance of the sigmoid take-off from the anal verge was associated with the distances of the sacral promontory (P<0.001) and peritoneal reflection (P<0.001) from the anal verge. The cancer distributions of patients varied widely with the application of different definitions. The point of sigmoid take-off is an intuitive landmark influenced by individual factors. The measurement of the sigmoid take-off by different researchers in both CT and MRI revealed good consistency. Further studies regarding the clinical significance of this definition are still needed.