Submucosal tunneling endoscopic resection (STER) is effective for resecting gastric subepithelial lesions (SELs) but requires precise tunnel orientation. Misdirected tunneling is a common challenge, particularly for small lesions, in large or roomy organs such as the stomach, and in procedures performed by trainees. Loss of direction can significantly prolong procedure time and lead to complications including bleeding and / or mucosal breach, making safe closure difficult. Rescue techniques for regaining orientation in such situations have not been adequately described. We report the innovative use of indocyanine green (ICG) which appears emerald green under white-light endoscopy to localize a missed lesion and redirect a tunnel during STER.
A small proximal gastric body SEL on posterior wall was planned for STER. A mucosal incision was made below the gastroesophageal junction (GEJ) and tunneling was commenced. The tunnel deviated from the intended plane, resulting in loss of lesion orientation and a small mucosal breach, complicating closure. As a rescue strategy, 1.25 mg/mL ICG was injected around the lesion using a direct transluminal approach and retroflexion. STER was continued using white light endoscopy, relying on ICG’s distinctive green color under white light.
On re-entering the tunnel, the emerald green ICG staining clearly delineated the correct trajectory, enabling precise redirection toward the SEL. The SEL was thus identified and resected enbloc. Mucosal closure was completed successfully, and the patient had an uneventful recovery.
White-light ICG marking is a safe, easily available, non-allergenic adjunct for real-time localization during challenging STER cases. ICG dissipates naturally without leaving foreign material, and unlike India ink, it does not trigger inflammatory reactions, abscesses, or adhesions if minor leakage occurs into the peritoneum. Methylene blue has already stained the submucosa blue – ICG offers a different color which stands out over and above the blue. This technique therefore offers an effective rescue method to manage misdirected tunneling, reduce complications, procedure time and enhance procedural success representing a meaningful innovation in third-space endoscopy.