Differentiation of colonic polyps by confocal laser endomicroscopy

Background and study aim: The real-time identification and removal of adenomas is a cost-effective strategy to improve the prognosis of colorectal cancer. Confocal laser endomicroscopy (CLE) could provide real-time histological-level observation. We aimed to evaluate the efficacy of CLE diagnosis using a simple classification system that differentiates adenomas from non-neoplastic polyps with intravenous fluorescein staining alone.

Patients and methods: An endoscope integrated confocal laser microscopy system was used in this study. CLE images of 35 colonic polyps, including 15 hyperplastic polyps and 20 adenomas confirmed by histology, were first evaluated to develop criteria for diagnosis of neoplastic and non-neoplastic polyps. The diagnostic criteria included goblet cell depletion, villous architecture, and microvascular alterations. We then performed a prospective study of colonic polyps found during CLE and classified them according to the established criteria. A total of 115 patients with 115 colonic polyps were included. The real-time CLE diagnosis was compared with that from histology. The stored CLE images were evaluated later by a blinded observer.

Results: The sensitivity, specificity, positive predictive value, and negative predictive value of real-time CLE in identifying colonic adenomas were 93.9 % (95 % confidence interval [CI] 85.4 – 97.6), 95.9 % (95 % CI 86.2 – 98.9), 96.9 % (95 % CI 89 – 99), and 92.2 % (95 % CI 81 – 97), respectively, compared with histological results. Interobserver agreement between real-time and post-CLE still-image evaluation was excellent (kappa = 0.929). Goblet cell depletion alone had a sensitivity of 84.9 % (95 % CI 73 – 92) and a specificity of 87.8 % (95 % CI 75 – 95), as well as excellent interobserver agreement (kappa = 0.824).

Conclusions: Endoscope integrated CLE with fluorescein staining may reliably assist in the real-time identification of colonic adenomas. Among three diagnostic categories, goblet cell depletion can be used to distinguish adenomas and hyperplastic polyps.

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