Mapping the rectum: spatial analysis of transanal endoscopic microsurgical outcomes using GIS technology.

Transanal endoscopic microsurgery (TEM) is a technically challenging procedure hindered by rectal anatomic constraints. To study the relationship of lesion position with performance of TEM, a novel approach of spatial analysis using Geographic Information Systems (GIS) was developed. A retrospective review was conducted on 144 consecutive TEMs, analyzing clinical, pathologic, and positional characteristics. Two- and three-dimensional maps of rectal topology were developed. GIS was used for spatial analysis, accounting for regional position and clustering of lesions. Lesions were located at a mean distance of 9.3 +/- 4.9 (SD) cm from the dentate line, with an average size of 3.1 +/- 1.4 cm. Proximal regions were associated with prolonged operative time. Regions between the rectosigmoid junction and the peritoneal reflection were associated with peritoneal breach. In spatial regression analysis, regional characteristics that were significantly associated with operative time included distance, presence of cancers, and positive margins; peritoneal breach was significantly associated with lesion size and location; conversions were associated with distance (P < 0.05). Specific knowledge of lesion size and location in the context of anatomic relationships is important for optimizing operative intervention. GIS provides a valuable tool in organizing spatial information and can be extended into clinical research topics involving the distinction of anatomic relationships.