KAR Hybrid ESD-EMR: Circumferential Tip-of-Snare Incision

A 6-minute guide to knife-assisted resection (KAR): circumferential tip-of-snare incision, then snare lift for hybrid ESD-EMR.

Piecemeal EMR on a broad lateral spreading tumor often leaves you guessing about lateral margins. Full ESD is elegant, but not every unit needs a dedicated knife for every flat lesion. Knife-assisted resection (KAR), also called hybrid ESD-EMR or precut polypectomy, bridges that gap: create a circumferential mucosal incision with the tip of the snare (or a knife), let the lesion contract into a graspable mound, then finish with snare resection.

Why standard snare-first EMR fails these lesions

On a fold-based or flat lateral spreading tumor, opening a snare first often captures an incomplete margin. You trade speed for uncertainty about lateral clearance.

If the question is “will piecemeal EMR get the edge?” and the answer is “maybe,” that is the KAR moment. You are not committing to a full ESD dissection plane under the entire lesion. You are buying a free circumferential mucosal margin before the snare ever closes.

Klaus uses the tip of the snare for the incision in this demo, with a generous submucosal cushion as the safety layer. The clip is transcript-grounded teaching from the full-course KAR lecture (WP 181983).

Step 1: Build a high submucosal cushion

Inject until the flat lesion lifts cleanly. Dynamic injection (needle advanced with small back-and-forth scope motion) spreads fluid under the target and builds a “volcano” cushion without needing four formal quadrants every time. Inject enough to be safe, not just a token bleb.

Video moment @ 0:20

Significance: Cushion thickness is your perforation buffer for the circumferential incision that follows.

Step 2: Circumferential incision with 1-2 mm snare tip

Expose only about one to two millimeters of snare tip. Start with a clean tip and a little water to dissipate current. Incise around the lesion to leave a free lateral mucosal margin. You are drawing the oncologic outline first, not fishing with a wide open snare.

Video moment @ 0:55

Significance: The free lateral margin is what turns “hopeful EMR” into a planned R0-oriented hybrid resection.

Step 3: Let the lesion contract, then snare

After the ring incision, the lesion often contracts toward the center like a small fungus. A central top-up injection can thicken the cushion further and improve vertical separation. Open the snare into the incision groove, lift, and complete with EMR-style snare resection (with water for safety before the final cut).

Video moment @ 1:40

Significance: Contraction is a feature of KAR, not a complication. It is why the snare works after the ring cut.

The result you want in the note looks like this:

Resection note line: KAR (hybrid ESD-EMR): submucosal lift; circumferential tip-of-snare mucosal incision with free lateral margin; snare completion; blue submucosal plane maintained.