Diagnostic performance of indigo carmine-assisted texture and color enhanced magnified imaging for superficial non-ampullary duodenal epithelial tumors

Background: Superficial non-ampullary duodenal epithelial tumors (SNADETs) are increasingly detected with advances in endoscopic imaging. However, the preoperative diagnosis remains challenging. Indigo carmine-assisted texture and color enhancement imaging (IC-TXI) is a novel modality that enhances mucosal contrast and topography. Objectives: To evaluate the diagnostic performance of IC-TXI for identifying Vienna classification (VCL) C4/5 SNADETs based on surface morphology. Design: Single-center retrospective study. Methods: This study analyzed 111 consecutive SNADETs resected between March 2021 and August 2024. IC-TXI images were assessed for abnormal surface structure, component size difference (>3-fold), and invisible surface pattern. Significant findings were defined as the coexistence of abnormal surface structure and component size or invisibility. Diagnostic performance was evaluated using histopathological VCL classification as the reference. Results: Ten (9.0%) lesions were classified as VCL C4/5. IC-TXI demonstrated a sensitivity of 50.0%, specificity of 97.0%, positive predictive value of 62.5%, negative predictive value of 95.1%, and accuracy of 92.8% for identifying VCL C4/5 lesions. Abnormal surface structure alone was observed in 5/10 (50.0%) VCL C4/5 lesions, abnormal size difference alone in 6/29 (20.7%), and invisible surface structure in 1/3 (33.3%). These findings suggest that abnormal surface structure may be diagnostically relevant than component size variation, and invisibility may have malignant potential. Conclusion: IC-TXI may serve as a practical method for the real-time exclusion of VCL C4/5 SNADETs. Given its high specificity and negative predictive value (NPV), this method may have the potential to reduce unnecessary biopsies and shorten observation time. However, rather than being considered a standard modality, IC-TXI should be regarded as an adjunctive tool to support clinical decision-making in combination with other clinical and endoscopic factors, particularly in light of its relatively low sensitivity (50.0%) observed in this study. Clinical trial registration: UMIN000041436.