The flat polyp: does too much

panese colleagues. Recently flat polyps have also been recognized in the West and have been noticed to have a higher incidence of significant neoplastic histology [1]. We describe two cases of a flat polyp missed or almost missed at colonoscopy, perhaps due to the effects of full insufflation. A 53-year-old healthy woman participated in a PillCam Colon 2 study in which PillCam Colon 2 capsule endoscopy (PillCam Colon 2; Given Imaging, Yoqneam, Israel) was compared with optical colonoscopy [2]. The indication for colonoscopy was painless rectal bleeding. The PillCam Colon 2 capsule study was performed in the morning, and after the capsule was passed in the afternoon a colonoscopy was performed. The patient received 2.5mg midazolam and 50mg pethidine intravenously. A Fujinon 250W colonoscope (Fujinon Corp., Saitama, Japan) was advanced to the ileum. The distal ileum and cecumwere carefully examined, and the appendiceal orifice and ileocecal valve were identified. Withdrawal time was 25 minutes. Internal hemorrhoids were present. No lesions were noticed in the cecum. When the PillCam Colon 2 study was reviewed we were notified that a 15-mm sessile polyp was seen in the cecum (●" Fig. 1). The patient was invited to a repeat colonoscopy for verification of this finding and removal of the polyp. The second colonoscopy confirmed the presence of a completely flat lesion 2 cm in size (●" Fig. 2). The histology examination identified a tubulovillous adenoma. In the second case, a 69-year-old woman underwent colonoscopy with an Olympus narrow-band imaging colonoscope (PCF180; Olympus Optical Co., Ltd., Tokyo, Japan) for surveillance after colonoscopic polypectomy, and a flat lesion was found in the ascending colon (●" Fig. 3) which was not removed during this colonoscopy because the colon was full of residual stool which could not be washed and sucked out. The patient was invited for repeat colonoscopy which, on full insufflation, could not at first detect the polyp (●" Fig. 4). Since the location of the polyp in relation to the ileocecal valve was well known from previous colonoscopy images, the search was continued for several minutes and acetic acid used, which finally revealed a rather large area of flat polyp, about 3 cm in size (●" Fig. 5). The lesion was finally removed piecemeal (●" Fig. 6) and proved on histology to be a sessile serrated adenoma. These cases show that when the colon is fully distended, flat lesions may be overlooked. The polyp in the first case, located in the nondistended cecum, was readily recognized at PillCam Colon 2 colonoscopy as a 1.5-cm sessile protruding finding. Yet this same polyp at colonoscopy in a distended cecum appeared as a completely flat lesion. The discrepancy was even more pronounced in the second case. It appears that insufflation of the colon at The flat polyp: does too much flattening occur with full air insufflation on colonoscopy?