Improved endoscopic resection of large flat lesions and early cancers using an external additional working channel (AWC): a case series.

En-bloc resection of large, flat lesions or early stages of cancer is challenging. No bimanual tasks are possible using standard endoscopes. Dual-channel endoscopes are not available everywhere and have a small distance between the channels. A new external additional working channel (AWC) (Ovesco, Tuebingen, Germany) was designed and developed potentially enabling bimanual tasks. Fixed to the tip of a standard gastroscope or pediatric colonoscope, a second endoscopic tool can be inserted through the AWC and used for tissue retraction during endoscopic resection. In the upper and lower gastrointestinal tract, endoscopic mucosal resection (EMR) with a modified grasp-and-snare technique and endoscopic submucosal dissection (ESD) were performed successfully using the AWC in eight patients. Complications were acute arterial bleeding post-EMR in two cases treated by endoscopic clipping. We conclude that a newly developed external additional working channel (AWC) enables endoscopic resection of large lesions in the upper and lower gastrointestinal tract. Potential benefits are its suitability for EMR and ESD, no need for a dual-channel endoscope and an adjustable distance of working channels.