THE DIFFERENCE IN COLON POLYP SIZE BEFORE AND AFTER REMOVAL

Background: Accurate knowledge of polyp size is important in assessing cancer risk in both clinical studies and individual patients. We soug ht to determine if a difference exists between the endoscopic estimati on of colon polyp size and the actual measurement after removal. Metho ds: We measured polyps in a systematic fashion. Using open biopsy forc eps as a guide, the largest diameter of 31 pedunculated polyps was est imated endoscopically. The polyp was then removed by snare polypectomy and directly measured by a technician who was blinded to the endoscop ic estimate. Each polyp was also measured after formalin fixation by a pathologist who was blinded to previous measurements. Results: There was a significant difference between the endoscopic estimates and the postpolypectomy measurements. Endoscopic estimates on average were 1.6 mm greater than the postpolypectomy measurements (p < 0.05), represen ting an 18% difference. Twenty-three of the 31 (74%) endoscopic estima tes were larger than the postpolypectomy measurements. There was not a significant difference between the postpolypectomy and postfixation m easurements. Conclusions: The size of polyps measured endoscopically i s significantly larger on average than postpolypectomy measurements. T his is most likely due to factors involved in the removal of the in vi vo polyp.