Utility of Combined Indigo Carmine and Red Dichromatic Imaging for Pit Pattern Diagnosis in Colorectal Lesions: A Comparison with Crystal Violet

ABSTRACT Crystal violet (CV) staining is the standard for diagnosing pit patterns in colorectal lesions; however, it has drawbacks such as complexity and potential carcinogenicity. This study aimed to evaluate whether combining indigo carmine (IC) with red dichromatic imaging (RDI) provides diagnostic performance comparable to CV. Fifty colorectal lesions resected at a single institution were evaluated using magnified images obtained using three methods: IC alone, IC + RDI, and CV. One representative image from each method was selected for each lesion, yielding 150 randomized images. Three expert endoscopists and three trainees independently assessed the pit pattern diagnosis and visibility scores (5‐point scale) as the primary evaluation parameters. Across all lesions, no significant differences were observed in the inter‐observer agreement rate of pit pattern diagnosis among the modalities in either group. However, for sessile serrated lesions (SSLs), IC + RDI tended to outperform CV in both groups. Regarding visibility scores, CV was significantly superior to RDI for both experts (4.33 vs. 3.67, p = 0.0014) and trainees (4.0 vs. 3.5, p = 0.019) across all lesions. For SSLs, experts evaluated visibility significantly higher for IC + RDI versus IC (4.67 vs 3.17, p = 0.021), although the difference between IC + RDI and CV was not significant. In conclusion, IC+RDI improved pit visibility in SSLs and showed diagnostic agreement comparable to CV in experts. However, CV remained superior for carcinoma, particularly among trainees. IC+RDI may be considered a safe and practical option in selected settings, especially for improving pit visualization in SSLs.