2005 Abstracts: Mapping the Rectum:Spatial Analysis of Transanal Endoscopic microsurgical Outcomes Using Geographic Information System (GIS) Technology
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Mapping the Rectum:Spatial Analysis of Transanal Endoscopic microsurgical Outcomes Using Geographic Information System (GIS) Technology
Sabha Ganai, Jane L. Garb, Prathima Kanumuri, Roshni S. Rao, Albert I. Alexander, Richard B. Wait, Baystate Medical Center / Tufts University School of Medicine, Springfield, MA
Purpose: Transanal endoscopic microsurgery (TEM) using the technique of Buess is a technically challenging minimally-invasive procedure requiring manipulation of parallel-positioned instruments within a 4cm-diameter, 20cm-long, operating rectoscope. It is uncertain whether location within the rectum correlates with difficulty in performing TEM. A novel approach of spatial analysis using Geographic Information System (GIS) technology was developed to study outcomes from this procedure.
Methods: A retrospective analysis of 144 consecutive patients between 11/1/1993 and 9/30/2004 undergoing TEM for both benign and malignant polyps was conducted after Institutional Review Board approval. Data including pathologic characteristics, size, distance, and clockface position of lesion, patient position, operative time, complications, conversions, and recurrence were abstracted, with performance of nonparametric statistical analysis. A map of rectal topology was developed highlighting anatomic features including anterior and posterior variability in location of the peritoneal reflection. Conversion from cylindrical to Cartesian coordinates was used to translate the map and data into three dimensions (3D). GIS was subsequently used for spatial analysis in both 2D and 3D. Results: Operative time greater than 90 minutes was associated with lesions greater than 18cm from the dentate line. Conversion to low anterior resection was associated with anterior lesions greater than 18cm from the dentate line. Peritoneal breech was associated with anterior and posterior lesions in the region between the peritoneal reflection and the rectosigmoid junction. Polyps greater than 4cm in size were associated with a longer operative time (Mann-Whitney p<0.0001) and were more likely to develop a recurrence (chi-square p<0.05). In spatial regression analysis, the only variable that was significantly related to operative time was size (p<0.001), which completely accounted for locational differences. Conclusions: Relating polyp location to rectal topology provides insight into the limitations of TEM. GIS provides a valuable tool in organizing spatial information and can be extended into clinical research topics involving distinction of anatomical relationships.
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