Blue laser imaging and linked color imaging improve the color difference value and visibility of colorectal polyps in underwater conditions

OBJECTIVES: Underwater endoscopic mucosal resection (UEMR) has become widespread for treating colorectal polyps. However, which observational mode is best suited for determining polyp margins underwater remains unclear. To determine the best mode, we analyzed three imaging modes: white light imaging (WLI), blue laser imaging (BLI) and linked color imaging (LCI).

METHODS: Images of consecutive colorectal polyps previously examined via these three modes before UEMR were analyzed according to the degree of turbidity underwater (transparent or cloudy). Color differences between the polyps and their surroundings were calculated using the Commission Internationale d'Eclairage Lab color space in which three-dimensional color parameters were expressed. Eight evaluators, who were blinded to the histology, scored the visibility from one (undetectable) to four (easily detectable) in both underwater conditions. The color differences and visibility scores were compared.

RESULTS: Seventy-three polyps were evaluated. Sixty-one polyps (44 adenomatous, 17 serrated) were observed under transparent conditions, and 12 polyps (7 adenomatous, 5 serrated) were observed under cloudy conditions. Under transparent conditions, the color differences for the BLI (8.5) and LCI (7.9) were significantly higher than that of the WLI (5.7; P <.001). The visibility scores for the BLI (3.6) and LCI (3.4) were also higher than that of the WLI (3.1; P<.0001). Under cloudy conditions, the visibility scores for LCI (2.9) and WLI (2.7) were significantly higher than that of the BLI (2.2; P<.0001 and P=0.04, respectively).

CONCLUSIONS: BLI and LCI were the better observational modes in transparent water; however, BLI was unsuitable for cloudy conditions.