Title:
Clip artifact after closure of large colorectal EMR sites: incidence and recognition.

Abstract:
Clip closure of large colorectal EMR defects sometimes results in bumpy scars that are normal on biopsy. We refer to these as "clip artifact." If unrecognized, clip artifact can be mistaken for residual polyp, leading to thermal treatment and potential adverse events.
To describe the incidence of and define predictors of clip artifact.
Review of photographs of scars from consecutive clipped EMR defects.
University outpatient endoscopy center.
A total of 284 consecutive patients with clip closure of defects after EMR of lesions 20 mm or larger and follow-up colonoscopy.
EMR, clip closure.
Incidence of clip artifact.
A total of 303 large polyps met the inclusion criteria. On review of photographs, 96 scars (31.7%) had clip artifact. Clip artifact was associated with increased numbers of clips placed (odds ratio for each additional clip, 1.2; 95% confidence interval, 1.02-1.38) but not polyp histology, size, or location. The rate of residual polyp by histology was 8.9% (27/303), with 21 of 27 scars with residual polyp evident endoscopically. The rate of residual polyp evident only by histology in scars with clip artifact (3/93; 3.2%) was not different from the rate in scars without clip artifact (3/189; 1.6%).
Retrospective design. Sites closed primarily with 1 type of clip. Single-operator assessment of endoscopic photographs.
Clip artifact occurred in the scars of approximately one-third of large clipped EMR sites and increased with number of clips placed. Clip artifact could be consistently distinguished from residual polyp by its endoscopic appearance.