BACKGROUND AND STUDY AIMS

Narrow band imaging (NBI) can accurately characterize colonic polyps using microvascular appearances. We aimed to assess whether the Kudo pit pattern classification is accurate when used with NBI (without dye-spray), and if microvascular appearances or NBI pit patterns maintain accuracy for polyp characterization at sizes < 10 mm.

PATIENTS AND METHODS

116 polyps < 10 mm in size were detected in 62 patients undergoing surveillance colonoscopy. The polyps were prospectively assessed using NBI and magnification for Kudo pit pattern (III-V neoplastic, I-II non-neoplastic) and vascular pattern intensity (VPI), a measure of microvascular density (strong VPI, neoplastic; normal or weak VPI, non-neoplastic). Sensitivity, specificity, and accuracy were calculated and compared with results from histopathology.

RESULTS

The mean polyp size was 3.4 mm (range 1 - 9 mm). Overall, NBI pit pattern sensitivity, specificity, and accuracy were 0.88, 0.91, and 89.6 %, respectively. Equivalent values for VPI were 0.94, 0.89, and 91.4 %. Results were similar when polyps were subdivided into diminutive polyps (size <or= 5 mm) and flat polyps. Combining both pit pattern and VPI improved the sensitivity (0.98, P = 0.06 versus NBI pit pattern alone). There was very good agreement between NBI pit pattern and VPI for prediction of dysplasia (kappa = 0.83). No evidence of a learning curve for VPI was found. The NBI pit pattern was better than the VPI at subclassifying hyperplastic from other non-neoplastic polyps (sensitivity 0.79 versus 0.56, respectively, P = 0.02), but accuracy was poor.

CONCLUSION

The NBI pit pattern and VPI are both highly accurate in characterizing neoplastic colonic polyps of < 10 mm, with VPI appearing to be simple to learn. NBI has the potential to replace conventional histology for small polyps.