Colonoscopy Practice and Quality: Colonoscopy Practice and Quality: Shape and Snare

0:00Welcome to Board Pearls. This is episode two of five of the Colonoscopy Practice and Quality chapter, in the Endoscopic Procedures module. This episode is describing a lesion before touching it, and then removing it with the right tool. The first patient is a woman with a large cecal lesion and a small adenoma, and her case shows why a lesion's shape predicts invasion, what the Paris classification describes and which shapes are dangerous, how the optical classifications read surface and vessels, how lateral spreading lesions differ in cancer risk, why cold snare is the default for small polyps, how endoscopic mucosal resection works and what a lesion that won't lift means, and how recurrence at the edge is prevented. The man from episode one, with a polyp on a thick stalk, shows when hot snare and a clip or loop are the safer choice. And the episode ends with when a lesion has to come out in one piece, by endoscopic submucosal dissection or an en bloc technique.

0:55Here's the patient. A sixty-three-year-old woman is having a surveillance colonoscopy. In her cecum there's a thirty-five-millimeter flat lesion spreading along the wall, its surface made of small, even granules, with a single raised nodule about twelve millimeters across near its center. Under narrow-band imaging, most of the lesion shows brown vessels surrounding a white pit pattern. Over the nodule, the vessels are irregular and uneven in caliber, but still present. She also has a six-millimeter adenoma in her transverse colon.

1:26She has a large granular lateral spreading lesion with a suspicious nodule, and before anyone touches it, it's described, because the description decides how it comes out. A lesion's morphology reflects its growth pattern, showing whether it has invaded vertically into the submucosa or spread horizontally along the mucosa, so it drives both the cancer risk and the choice of technique. The Paris classification is applied to every colorectal lesion before any resection decision, and the optical classifications describe its vessels and surface. Snaring first and describing later risks a piecemeal resection that can't be staged, in a lesion that needed staging.

2:03Her lesion's shape is described first, because shape alone can signal invasion. The Paris classes are zero-one-p, pedunculated; zero-one-s, sessile; zero-two-a, flat and slightly elevated; zero-two-b, completely flat and flush with the surrounding mucosa, which is rare; zero-two-c, flat and depressed; zero-three, ulcerated; and mixed forms, such as zero-one-s plus two-a, or zero-two-a plus two-c. Depression is the high-risk feature. Zero-two-c and mixed zero-two-a plus two-c lesions carry disproportionately high rates of submucosal invasion, because a depression reflects vertical growth into the submucosa rather than horizontal spread, so a depressed lesion has already started toward deep invasion when it's seen. Her lesion is flat and slightly elevated with a raised nodule, a mixed zero-two-a plus one-s, without depression.

3:00Her shape shows how the lesion grew, and her surface and vessels show whether cancer is already there. Optical diagnosis with narrow-band imaging classifies lesions in real time as benign or invasive. The NBI International Colorectal Endoscopic classification, NICE, has three types. Type one is hyperplastic or sessile serrated: pale or matching the surrounding mucosa, with no visible vessels or regular ones. Type two is adenoma: a brown surface with brown vessels surrounding a white pit pattern. Type three is deep submucosal invasive carcinoma: a disrupted, amorphous, or absent vascular pattern. The Japan NBI Expert Team classification, JNET, refines NICE into types one, two A, two B, and three, with two B and three indicating high cancer risk and prompting en bloc resection or surgical referral. The Kudo pit pattern, types one to five on chromoendoscopy, adds the surface pits, with type five indicating malignancy.

4:06Read together, those systems mark her nodule as the place that needs different handling. Most of her lesion is NICE type two. Her nodule's vessels are irregular but present, not the absent or amorphous pattern of type three, so they fit JNET two B: high risk, without frank deep invasion. NICE would call the nodule type two like the rest of the lesion, while JNET separates the ordinary two A pattern from the two B pattern that raises cancer risk, and that separation is what flags the nodule. A Kudo type five pattern over the nodule would have indicated malignancy, pointing toward en bloc resection or surgical referral. At the other end of the scale, a NICE type one or JNET type one lesion can be removed confidently with a cold snare on optical diagnosis alone.

4:57Her lesion's growth pattern then sets its cancer risk. A lateral spreading lesion is a non-polypoid lesion of ten millimeters or more that grows mainly sideways, and its cancer risk depends on its surface. Granular homogeneous lesions carry less than one percent risk, because the even granular surface reflects slow adenomatous growth with an intact basement membrane. Granular mixed nodular lesions carry five to ten percent, and the dominant nodule, a focal area larger than the surrounding granules, is the highest-risk site. Non-granular flat-elevated lesions carry about five percent. Non-granular pseudodepressed lesions carry a risk approaching thirty percent, the highest of any lateral spreading type, because the pseudodepressed look reflects rapid vertical expansion into the submucosa. Hers is granular mixed nodular, and the nodule with its JNET two B vessels is where any cancer is most likely to be.

5:52That risk sets her technique. Granular homogeneous lesions suit piecemeal endoscopic mucosal resection. Non-granular pseudodepressed lesions need resection in one piece, by en bloc endoscopic mucosal resection or endoscopic submucosal dissection, so the depth of invasion and the margins can be assessed. In mixed lesions like hers, the dominant nodule is the target, removed in one piece or biopsied. A NICE type three lesion, predicting deep invasion, is biopsied rather than snared piecemeal, and then resected in one piece if feasible or referred for surgery. Her report reads: a thirty-five-millimeter granular mixed nodular lateral spreading lesion in the cecum, Paris zero-two-a plus one-s, NICE two, with a JNET two B dominant nodule.

6:42Not every lesion she or the next patient has will be an adenoma, and serrated polyps carry their own recognition rules. Hyperplastic polyps are typically under five millimeters, distal in the rectosigmoid, and low risk, and up to twenty small distal hyperplastic polyps don't warrant shorter surveillance. Sessile serrated lesions are flat or slightly raised, mostly right-sided, and capped with mucus, and they progress through the CpG island methylator phenotype pathway, with a BRAF V600E mutation and MLH1 promoter methylation. So a flat eight-millimeter area under a yellow mucus cap in the right colon is washed, its edge defined, and removed, not mistaken for stool. Traditional serrated adenomas are rare, usually left-sided, bulky, and frond-like, uniformly dysplastic with eosinophilic cytoplasm, and often misclassified as tubulovillous adenomas because their growth patterns overlap. A bulky, frond-like, left-sided polyp reported as tubulovillous with eosinophilic cytoplasm raises the question of a traditional serrated adenoma, whose surveillance follows the serrated rules. Polyp histology and the cancer pathways are covered in chapter fifteen.

7:58Her small transverse adenoma is removed first, and the tool is chosen to avoid heat. Cold forceps can remove polyps under five millimeters, but used as a resection technique they tend to leave residual tissue, because the second bite misses adenoma the first one displaced. So cold snare is preferred for diminutive polyps and is the standard for polyps of four to ten millimeters. It cuts mechanically at the junction of mucosa and submucosa, limiting injury to the superficial submucosa and avoiding the thermal damage that drives delayed bleeding and post-polypectomy electrocoagulation syndrome, with complete resection that's non-inferior. It's increasingly used in multiple bites or piecemeal for selected sessile lesions of ten millimeters or more. Her six-millimeter adenoma is removed with a cold snare.

8:49A pedunculated polyp needs a different tool, because its stalk carries an artery. The forty-seven-year-old man from episode one, besides his ascending colon adenoma, has a twenty-two-millimeter pedunculated sigmoid polyp on a thick stalk. Hot snare is reserved for pedunculated polyps over ten millimeters, because the stalk contains a defined feeding artery that bleeds briskly when cut cold, while current seals it as the snare cuts. A thick stalk warrants prophylactic mechanical hemostasis, a clip or detachable loop at the base, before it's cut. His polyp gets a detachable loop and a hot snare, without bleeding. This is the one setting where thermal energy is the safer choice: in a small sessile polyp, heat only adds injury, while in a thick stalk it closes the artery. Hot snare is also used for selected sessile lesions where cold snare can't achieve complete resection, such as very firm or fibrotic mucosa, at the cost of more delayed bleeding and electrocoagulation syndrome.

9:48Her cecal lesion gets the standard technique for its size, endoscopic mucosal resection, EMR, used for sessile and lateral spreading lesions of ten millimeters or more without high-risk features. A submucosal cushion of saline with indigo carmine or methylene blue, sometimes with dilute epinephrine, is injected under the lesion. The cushion lifts it away from the muscularis propria, lowering perforation risk; it tamponades small vessels, lowering immediate bleeding; and it gives the snare a tissue plane to close over. The dye shows the resection plane.

10:22A lesion that won't lift changes the plan, because the lift is also a test. The non-lifting sign is a contraindication to EMR: failure to lift means either deep submucosal invasion tethering the mucosa to the muscle, or fibrosis from prior intervention or chronic inflammation. Snaring across a non-lifting lesion risks incomplete resection and perforation, so the next step is biopsy and referral for surgery or endoscopic submucosal dissection. A nodule that stays flat while the field lifts around it is a focal non-lifting sign at the highest-risk site, and calls for the same biopsy and referral. Her lesion lifts well, including under the nodule, so the nodule is removed in one piece first, intact for the pathologist, and the granular field is removed piecemeal around it.

11:10Her margin is then treated, because recurrence starts at the edge. Snare-tip soft coagulation runs the closed snare tip in soft-coagulation mode around the margin of the EMR defect, ablating microscopic nests of adenoma that are invisible to the eye but documented on histology. A randomized trial showed about a fourfold reduction in adenoma recurrence at first surveillance. Cold avulsion with snare-tip soft coagulation adds mechanical removal of residual flat tissue at the margin before the remaining defect is treated. Her entire margin is treated.

11:41If her lesion recurs on the scar, a technique without injection is needed, because scar won't lift. Underwater EMR resects with the lumen filled with saline instead of a submucosal injection, and the relaxed mucosa floats away from the muscularis propria to form a natural cushion. It suits lesions where injection has failed because of scar after a prior EMR or fibrosis rather than invasion, and difficult lesions at flexures or behind folds. For lesions of ten to thirty millimeters, it matches conventional EMR for complete resection, with fewer injection problems and shorter procedures. It's contraindicated in deep cancer, because water doesn't protect against perforation when the muscularis propria is involved. A fibrotic, non-lifting recurrence on her scar at six months would suit it.

12:27Some lesions have to come out in one piece, because the pathologist needs an intact specimen to stage them. Endoscopic submucosal dissection, and en bloc EMR with band ligation or traction, are reserved for lesions with a high cancer risk: rectal lesions, where curative resection in one piece can avoid a permanent stoma; lesions with a dominant nodule; depressed Paris classes; non-granular pseudodepressed lateral spreading lesions; and large lesions where fragments would lose the orientation needed for staging. A single intact specimen keeps its margins, so the pathologist can assess the depth of invasion, lymphovascular invasion, and tumor budding.

13:08Whether endoscopic submucosal dissection has cured a lesion is judged against defined criteria. The Japanese curative criteria for colorectal dissection are resection in one piece, negative vertical and lateral margins, well or moderately differentiated histology, no lymphovascular invasion, and either intramucosal disease or submucosal invasion of less than one thousand microns. When all are met, the risk of nodal metastasis falls below one percent and surgery isn't needed. Western adoption has been slower because of a longer training curve, procedures of ninety to one hundred twenty minutes compared with twenty to thirty for EMR, and the alternative of surgery with low operative mortality, but its role has grown for rectal and high-risk colonic lesions at high-volume centers. Had her lesion been in the rectum, there'd have been an added reason for dissection: curative resection in one piece could spare her a rectal operation and a stoma.

14:06Here are the traps the boards set in lesion recognition. A lesion is described before it's snared. Depression is the high-risk shape for invasion. NICE or JNET type three, and Kudo type five, aren't removed with a piecemeal snare. A non-granular pseudodepressed lesion isn't removed piecemeal, and the dominant nodule in a mixed lesion is targeted. A granular homogeneous lesion, with less than one percent cancer risk, isn't overtreated. Small distal hyperplastic polyps don't shorten surveillance. A mucus-capped sessile serrated lesion isn't mistaken for stool, and a traditional serrated adenoma isn't accepted as tubulovillous.

14:46For resection, the traps are these. Diminutive polyps are removed with a cold snare, not cold forceps. Hot snare isn't used for small sessile polyps. A thick stalk gets a clip or loop before it's cut. A non-lifting lesion isn't snared, because non-lift can mean cancer or scar. The EMR margin is treated with snare-tip soft coagulation. Underwater EMR isn't used for suspected deep invasion. A depressed lesion isn't removed piecemeal. And rectal lesions have the strongest reason for resection in one piece, judged against the curative criteria.

15:22So, start to finish. Describe every lesion by Paris class and optical pattern first. Depression, NICE or JNET type three, Kudo type five, and non-granular pseudodepressed lesions predict invasion and need resection in one piece or surgery. Granular homogeneous lesions carry less than one percent risk and suit piecemeal EMR, while granular mixed nodular lesions carry five to ten percent, with the dominant nodule as the target. Hyperplastic polyps are small and distal, sessile serrated lesions are flat, right-sided, and mucus-capped, and traditional serrated adenomas are bulky, left-sided, and easily mislabeled.

16:03Cold snare polyps under ten millimeters rather than using forceps. Use hot snare for pedunculated polyps over ten millimeters, with a clip or loop on thick stalks. Use EMR for lesions of ten millimeters or more without high-risk features, removing any dominant nodule in one piece, and treat the margins with snare-tip soft coagulation to cut recurrence about fourfold. Biopsy and refer a non-lifting lesion. Use underwater EMR for scarred lesions without deep invasion, and dissection or en bloc techniques for suspected superficial invasion, especially in the rectum, judged against the curative criteria.

16:41Episode three is what happens when the pathology says cancer, and then when to look again: the malignant polyp and surveillance intervals.

16:50For 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.