Colonoscopy Practice and Quality: Polyp Recognition and Resection Technique

0:00Welcome to Board Pearls. This is episode two of five of the Colonoscopy Practice and Quality chapter, in the Endoscopic Procedures module. In this episode we cover polyp recognition and resection technique: Paris morphology classification, NICE and JNET endoscopic prediction, Kudo pit pattern, the lateral spreading granularity types, and resection technique selection by size and morphology, with cold snare for small polyps and EMR for larger lesions.

0:28Start with what your eye is doing before the snare opens. You are looking at a polyp, and the entire downstream decision tree comes from the question your eye is silently answering. Has this lesion grown horizontally along the mucosa, or has it grown vertically into the submucosa. That distinction underlies everything that follows. Horizontal growth is slow, controlled adenomatous expansion with the basement membrane still intact. Vertical growth means the lesion is already moving toward the muscularis mucosae and the lymphatics that sit just beneath it. Morphology is how vertical growth shows itself before histology confirms it.

1:06The Paris classification is the structural taxonomy that names what you are seeing, and every subtype hangs off a zero prefix. Pedunculated polyps are zero-I-pedunculated, with a stalk holding the head off the wall. Sessile polyps are zero-I-sessile, sitting on the wall without a stalk. Flat-elevated lesions are zero-two-a. Completely flat lesions flush with the mucosa are zero-two-b, and these are uncommon. Depressed lesions are zero-two-c. And mixed forms exist, with zero-two-a-plus-c being the most clinically important mixed pattern. Zero-three is ulcerated.

1:43The teaching inside that list is the depressed morphologies. Paris zero-two-c and the mixed zero-two-a-plus-c carry disproportionately high rates of submucosal invasion, and the reason is the one we just named. A depression on the surface is what vertical growth into the submucosa looks like from above. The lesion has pulled down into the wall rather than out into the lumen. By the time you can see the depression, the path to deep invasion has already started. So a flat-elevated lesion with a central depression is not a piecemeal EMR target. The next move is en bloc resection or surgical referral.

2:18The optical-pattern classifications extend the same idea to the vessels and the surface. NICE, the narrow-band imaging international colorectal endoscopic classification, has three types. Type one is hyperplastic or sessile serrated, pale or matching the surrounding mucosa, with vessels that are absent or regular. Type two is adenoma, a brown surface with brown vessels surrounding a white pit pattern. Type three is deep submucosal invasive carcinoma, where the vascular pattern is disrupted, amorphous, or absent. The mechanism is biologic. Adenomatous neovascularization is a brown vascular meshwork around an orderly white pit pattern. Deep invasion destroys that architecture, so the vessels become disorganized or disappear because the tumor has outgrown its own vascular supply and the surface pattern is fragmenting.

3:09JNET, the Japan NBI Expert Team classification, refines NICE into four categories: one, two-A, two-B, and three. Two-B and three are the high-risk reads, with two-B indicating high-grade dysplasia or superficial submucosal invasion and three indicating deep submucosal invasion. The clinical principle behind both systems is that real-time optical diagnosis can guide resection technique without waiting for pathology. A NICE one or JNET one lesion can be confidently treated with cold-snare polypectomy. A NICE three or JNET three lesion is no longer an endoscopic problem; it is a staging problem.

3:50Kudo pit pattern is the chromoendoscopy companion, running from type one through type five. The teaching is the endpoint. Kudo type five indicates malignancy. The rest of the Kudo scale tracks the same progression from regular round pits in normal mucosa through tubular and gyrus-like patterns in adenomas to disorganized non-structural patterns in cancer.

4:10Now apply the same morphology-is-growth-pattern logic to lateral spreading lesions, where the cancer-risk numbers actually matter. A lateral spreading lesion is ten millimeters or larger and predominantly horizontal in growth. They subdivide by surface granularity, and the granularity is doing real work. Granular homogeneous lateral spreading lesions carry under one percent cancer risk, because a granular surface reflects controlled slow adenomatous growth with the basement membrane intact. Granular mixed-nodular lesions carry five to ten percent risk. The dominant nodule is a focal area larger than the surrounding granules. That nodule is where the risk concentrates. The dominant nodule is therefore the en bloc target within the lesion. Non-granular flat-elevated lesions carry roughly five percent risk. Non-granular pseudodepressed lesions carry close to thirty percent risk, the highest of the lateral spreading morphologies, because the pseudodepressed appearance reflects rapid vertical clonal expansion into the submucosa relative to the horizontal mucosal spread. Same principle as the Paris depressed lesions, applied to a larger, flatter substrate.

5:20That morphology-driven risk gradient then dictates the resection plan. Low-risk granular homogeneous lesions can be managed with piecemeal EMR because cancer risk is low and en bloc orientation is not needed for staging. Non-granular pseudodepressed lesions warrant en bloc resection so that invasion depth and margin status can be accurately assessed by the pathologist. The dominant nodule on a mixed-nodular lesion gets the en bloc treatment even when the rest of the lesion is taken piecemeal.

5:48That brings us to resection technique selection. The choices escalate by size, morphology, and the cancer-risk read from your optical diagnosis. The principles running underneath are mechanical versus thermal, depth control, and specimen integrity.

6:04Start with the diminutive lesion under five millimeters. Cold forceps biopsy used to be the standard, and it should not be. Forceps biopsy of small polyps tends to leave residual adenomatous tissue, because the second bite often misses tissue the first bite displaced rather than removed. Cold snare polypectomy is preferred for diminutive polyps and is the standard for polyps four to ten millimeters. The mechanism is what makes cold snare so good. The wire mechanically transects the polyp at the mucosa-submucosa interface through pure pressure, with no electrosurgical energy involved. Depth of injury is limited to the superficial submucosa. There is no thermal damage, which means delayed bleeding falls dramatically, and post-polypectomy electrocoagulation syndrome essentially does not happen. Complete resection rates are non-inferior to hot snare in this size range. So cold snare wins on safety without losing on cure. And cold snare is increasingly being applied to sessile lesions ten millimeters or larger, with multiple-bite or piecemeal cold technique replacing hot snare for selected non-pedunculated lesions.

7:12Hot snare is reserved for the one situation where cold snare cannot do the job. A pedunculated polyp over ten millimeters has a defined feeding artery running through the stalk. Cold mechanical transection of a vascularized stalk produces brisk bleeding from the central vessel, and the snare has no way to seal it. Electrosurgical energy coagulates the vessel as the wire cuts. Thick stalks warrant prophylactic mechanical hemostasis with a clip or detachable loop at the base before transection, because even with cautery the central artery can bleed. The cost of hot snare is the same energy that seals the vessel. It increases delayed bleeding and post-polypectomy electrocoagulation syndrome compared with cold snare. So hot snare is the right tool only when the anatomy demands it.

7:58For sessile lesions and lateral spreading lesions ten millimeters or larger without high-risk features, endoscopic mucosal resection is the standard. The technique is to inject submucosal fluid until the lesion lifts off the muscularis propria. The fluid is usually saline with indigo carmine or methylene blue, sometimes with dilute epinephrine. Then snare-resect the elevated mucosa above the cushion. The submucosal cushion does three things at once. It lifts the lesion away from the muscle layer, which reduces perforation risk. It tamponades small vessels, which reduces immediate bleeding. And it gives the snare wire a tissue plane to close over, which makes clean capture mechanically easier. The dye outlines the resection edge so you can see the boundary as you work.

8:43The non-lifting sign is the most important diagnostic moment during EMR. You inject, and the lesion does not elevate. That tells you one of two things. Either there is deep submucosal invasion fixing the mucosa to the muscularis propria, or there is fibrosis from prior intervention or chronic inflammation tethering the layers together. Either way, snare resection across a non-lifting lesion risks incomplete resection and perforation. The next step is to biopsy the lesion and refer for surgery or ESD, depending on the read.

9:16Two technique additions reduce local recurrence at the EMR margin. Snare-tip soft coagulation uses the closed snare tip in soft-coagulation mode to thermally treat the EMR defect edge after resection. Randomized data showed roughly a four-fold reduction in adenoma recurrence at first surveillance with margin thermal ablation. The mechanism is that microscopic adenomatous nests at the resection margin, invisible to the eye but documented histologically, are killed by the thermal pass. Cold avulsion plus snare-tip soft coagulation combines mechanical removal of residual flat tissue at the margin with subsequent thermal treatment of what remains.

9:57Underwater EMR is the alternative when standard submucosal injection has failed. You fill the lumen with saline rather than air, and the relaxed mucosa floats away from the muscularis propria through buoyancy, creating a natural cushion without injection. The snare captures and resects through the water-immersed plane. It is particularly useful for post-EMR scar lesions and for fibrotic non-lifting lesions where the non-lift is from prior intervention rather than deep invasion. Randomized data show comparable complete resection rates with underwater EMR versus conventional EMR for lesions ten to thirty millimeters, with the advantage of fewer injection issues and shorter procedure times. Underwater EMR does not protect against perforation when the lesion involves the muscularis propria, so it is contraindicated when deep cancer is suspected.

10:45Endoscopic submucosal dissection and en bloc EMR with band ligation are reserved for high-cancer-risk lesions where specimen integrity for accurate staging is the point. The key indications are rectal lesions where organ-preserving cure avoids a permanent ostomy, dominant nodule lateral spreading lesions, and depressed Paris classes including zero-two-c and mixed zero-two-a-plus-c. Non-granular pseudodepressed lateral spreading lesions also qualify. So do large lesions where piecemeal resection would lose orientation for staging. The reason to insist on en bloc is mechanical. Piecemeal resection fragments the specimen, and the pathologist cannot reliably measure invasion depth or assess margins across fragments. En bloc preserves the lesion as a single piece with intact margins, which is what depth-of-invasion and lymphovascular-invasion assessment requires.

11:38The Japanese curative criteria for colorectal ESD define when endoscopic resection alone is sufficient. The lesion must be removed en bloc with histologically negative vertical and lateral margins. Histology must be well or moderately differentiated. There must be no lymphovascular invasion. And the disease must be either intramucosal or with submucosal invasion under one thousand microns. When all four criteria are met, lymph node metastasis risk falls below one percent, and surgery is not required. Western adoption of ESD has been slower than Asian adoption. The training curve is long. Procedures run ninety to one hundred twenty minutes versus twenty to thirty for EMR. And the surgical alternative has low operative mortality in the West. The role has expanded for rectal lesions and high-risk colonic lateral spreading lesions at high-volume centers.

12:31Pull the recognition-and-resection half together. Polyp management begins as a reading task: morphology tells you whether growth has been horizontal or vertical, and vertical growth is what carries cancer risk. Paris, NICE and JNET, Kudo, and the lateral spreading granularity types are all ways of reading that same growth pattern from different angles. The resection technique you pick is the response to what the optical read tells you. Cold snare handles the diminutive and small range on safety grounds, hot snare is reserved for the vascularized pedunculated stalk, EMR is the standard for sessile and lateral spreading lesions without high-risk features, and en bloc resection by ESD or band-ligation EMR is reserved for when specimen integrity is needed for staging.

13:17The next episode picks up the moment the pathology comes back and the polyp turns out to hold cancer. The anatomic rule that makes the muscularis mucosae the line that matters, the Kikuchi and Haggitt depth systems, the high-risk histologic features including tumor budding, and the surveillance intervals that calibrate the next exam to the worst lesion you found.

13:39For the full chapter, the practice vignettes, and the topic-tagged question bank, head to board pearls dot com. You'll find the rest of the series on Apple Podcasts, Spotify, or wherever you listen to podcasts. That brings us to the end of episode two of five of chapter thirty, and I'll see you in the next one.