Traditional transparent caps in colonic endoscopic submucosal dissection (ESD) often fail to provide sustained mucosal retraction, leading to poor submucosal visualization and increased risk of incomplete resection or perforation, especially in large or fibrotic lesions.

We developed a novel, low-cost “peaked cap”—a custom-designed transparent cap with a peaked extension adhered using nail art adhesive—that enables continuous and active retraction of the mucosal flap during ESD, thereby maintaining a clear submucosal visual field and facilitating precise dissection.

The “peaked cap” was successfully applied in a 77-year-old female with a 3×4 cm laterally spreading tumor in the transverse colon. The device allowed smooth submucosal dissection, excellent visibility, and complete en bloc resection without adverse events. Histopathology confirmed tubulovillous adenoma with clear margins.

The “peaked cap” is an effective, economical, and easily reproducible innovation that enhances submucosal exposure and safety during colonic ESD, offering a practical solution particularly valuable in resource-limited settings.