Introduction
In colorectal epithelial neoplasms, lesions classified as type 2B according to the Japan Narrow Band Imaging (NBI) Expert Team classification (JNET), which are characterized by irregular microsurface or microvascular patterns, are often difficult to diagnose accurately using NBI magnifying endoscopy (ME) alone. Therefore, supplementary pit pattern diagnosis using crystal violet (CV)-stained ME (CV-ME) is recommended. However, CV is potentially carcinogenic, and CV-ME is relatively complex and time-consuming. Acetic acid (AA)-enhanced NBI ME (ANBI-ME) has been proposed as a simpler and safer alternative. Based on our previous study identifying 4.5% AA as the optimal concentration[1], this study prospectively evaluated the diagnostic utility of 4.5% ANBI-ME as a substitute for CV-ME (UMIN registration number: 00045621).
Aims & Methods
From October 2021 to March 2024, colorectal lesions classified as JNET type 2B or 3 during colonoscopy were prospectively enrolled until 300 cases were included. Each lesion underwent ANBI-ME with 4.5% AA, followed by CV-ME. The area of suspected deepest invasion was selected, and one representative image from ANBI-ME and one from CV-ME were independently assessed by two expert endoscopists blinded to histopathology. Intermethod and interobserver agreement were evaluated using Cohen’s weighted kappa. Diagnostic accuracy for each modality was calculated using the individual and consensus diagnoses of the two experts (McNemar’s test). AA whitening duration (AD), representing a reversible mucosal reaction, was measured during ANBI-ME and analyzed by histological depth (low-grade dysplasia [LGD], high-grade dysplasia [HGD], superficial submucosal invasive carcinoma [SMs], and deep submucosal invasive carcinoma [SMd]) using Kaplan–Meier analysis and the log-rank test.
Results
After excluding four unresected lesions, 296 lesions were analyzed. Median lesion size was 18 mm. Locations included the cecum (30), ascending colon (47), transverse colon (69), descending colon (13), sigmoid colon (73), and rectum (64); 122 lesions were elevated and 174 flat. Histological diagnosis included 77 LGD, 145 HGD, 18 SMs, and 56 SMd. Good agreement was observed between modalities (κ = 0.65 and 0.62) and between observers (κ = 0.78 for ANBI-ME, κ = 0.66 for CV-ME). Consensus was reached in 216 ANBI-ME and 192 CV-ME cases. Diagnostic accuracy was significantly higher with ANBI-ME than CV-ME for both observers (81% vs. 76%, p = 0.028; 75% vs. 69%, p = 0.025). Among consensus cases, ANBI-ME also showed higher accuracy (66% vs. 57%, p < 0.01). Median AD (in seconds) was 52 for LGD, 80 for HGD, 132 for SMs, and 107 for SMd, with a significantly shorter duration observed in LGD (p < 0.001).
Conclusion
ANBI-ME demonstrated diagnostic performance equivalent to or superior to CV-ME for colorectal lesions classified as JNET type 2B or 3. In addition, AA whitening duration (AD) may complement the assessment of histological depth of invasion.
References
[1]. Shimizu T, Yamagata T, Kanno Y, et al. A single-center pilot study on the efficacy and safety of acetic acid-enhanced magnifying endoscopy with narrow-band imaging for diagnosis of colorectal epithelial neoplasms. Gastrointest Endosc. 2025;101(2):416-424.