Mapping the Rectum: Spatial Analysis of Transanal Endoscopic Microsurgical Outcomes Using GIS Technology Sabha Ganai, M.D., Jane L. Garb, M.S., Prathima Kanumuri, M.D., Roshni S. Rao, M.D., Albert I. Alexander, M.D., Richard B. Wait, M.D., Ph.D. Transanal endoscopic microsurgery (TEM) is a technically challenging procedure hindered by rectal an- atomic constraints. To study the relationship of lesion position with performance of TEM, a novel ap- proach of spatial analysis using Geographic Information Systems (GIS) was developed. A retrospective review was conducted on 144 consecutive TEMs, analyzing clinical, pathologic, and positional character- istics. 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 dis- tance of 9.3 6 4.9 (SD) cm from the dentate line, with an average size of 3.1 6 1.4 cm. Proximal regions were associated with prolonged operative time. Regions between the rectosigmoid junction and the peri- toneal reflection were associated with peritoneal breach. In spatial regression analysis, regional character- istics 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. ( J GASTROINTEST SURG 2006;10:22–31) Ó 2006 The Society for Surgery of the Alimentary Tract KEY WORDS: Transanal endoscopic microsurgery, rectal anatomy, rectal neoplasm, health geographics, geographic information systems Transanal endoscopic microsurgery (TEM) using the technique of Buess is a minimally invasive proce- dure utilized as an alternative to traditional transanal approaches in the excision of rectal neoplasms. De- spite sophisticated features including binocular ste- reoscopic magnification, precise instrumentation, and improved access to proximal lesions, 1,2 the pro- cedure is technically challenging and has shown lim- ited incorporation into surgical management compared with other minimally invasive procedures. Intrinsic limitations in TEM must be considered, re- lated to the dimensions of the scope and the natural spatial conflicts that occur when manipulating multi- ple parallel-positioned instruments. The angled op- tic also requires optimal patient positioning, with the lesion situated in a dependent position. It is un- certain whether the location of the lesion within the rectum influences difficulty in performing the procedure. Geographic Information Systems (GIS) has been used in various studies related to epidemiology, ana- lyzing disease patterns, spatiotemporal relationships with health outcomes, and relationships of disease incidence with various environmental factors. 3 In or- der to test the hypothesis that the location of rectal lesions influences performance of TEM, a novel approach to spatial analysis of the rectum was developed using GIS technology. METHODS Clinical Data Acquisition After institutional review board approval, a retro- spective review was conducted on all patients Presented at the Forty-Sixth Annual Meeting of The Society for Surgery of the Alimentary Tract, Chicago, Illinois, May 14–18, 2005 (poster presentation). From the Department of Surgery, Baystate Medical Center/Tufts University School of Medicine, Springfield, Massachusetts. Reprint requests: Richard B. Wait, M.D., Ph.D., Department of Surgery, Baystate Medical Center, 759 Chestnut Street, Springfield, MA 01199. e-mail: Richard.Wait@bhs.org 22 Ó 2006 The Society for Surgery of the Alimentary Tract Published by Elsevier Inc. 1091-255X/06/$dsee front matter doi:10.1016/j.gassur.2005.08.030