Why Does Esophageal Mucosa Appear Blue-Green in Young Men during Observation on Blue Light Imaging? The Relationship with Hemoglobin Concentration

Nishiwaka E, Yamanaka H and Onizuka N

Published on: 2025-12-25

Abstract

When observing the esophagus in a mid-to-distant view under BLI (Blue Light Imaging), there are variations in color ranging from brownish to bluish-green. Since these differences in color may be attributed to hemoglobin (Hb) concentration, we aimed to elucidate the relationship between the color of the esophageal mucosa observed under BLI and the Hb concentration in the blood. Fifty cases were analyzed by calculating the mean RGB color values from endoscopic images, and the color was quantified using the Green/Red (G/R) ratio and Blue/Red (B/R) ratio. The results demonstrated a significant positive correlation between the G/R ratio in BLI images and Hb concentration (correlation coefficient 0.628, p=0.016), with a similar trend observed for the B/R ratio (correlation coefficient 0.612, p=0.020). Additionally, although less pronounced than the correlation with Hb, a significant positive correlation was found between these ratios and hematocrit. No significant correlations were observed under white light or Linked Color Imaging (LCI), suggesting that these phenomena are specific to BLI. These findings imply that the color of BLI images may reflect Hb concentration, opening possibilities for non-invasive estimation of Hb and real-time prediction using AI. This study demonstrates a novel approach for estimating Hb concentration through image analysis, with potential applications across various clinical fields.