2015-05-08 20:02:22 UTC

Nonpolypoid (Flat) Colorectal Neoplasms: Optimizing Detection And Removal

May 9, 2015

Tips to help gastroenterologists optimize the detection and removal of flat neoplasms.

G.E. Boeckxstaens, MD, PhD

Sarah K. McGill, MD, MS

Assistant Professor of Medicine, Division of Gastroenterology and Hepatology, University of North Carolina at Chapel Hill

Nonpolypoid colorectal neoplasms — those whose shape is slightly raised, completely flat or depressed compared to the surrounding mucosa — can present challenges for even seasoned gastroenterologists. Their subtle morphologies can make detection tricky. Complete resection may require different techniques than those used for sessile polyp removal. As a trainee and faculty member, I have studied flat lesions and now routinely remove them in my practice. In this article, I aim to provide a perspective on why they are important and how gastroenterologists can optimize their detection and removal.

Flat Neoplasms: How Prevalent Are They?

Current literature supports that nonpolypoid colorectal neoplasms (NP-CRNs) are relatively common, have more advanced pathology than their polypoid counterparts, and contribute to interval colon cancer. NP-CRNs, once thought to be rare, are now known to be common in Western populations. In prospective colonoscopy studies in the U.S. and Europe, 6 to 24 percent of patients had at least one nonpolypoid colorectal neoplasm. In addition, NP-CRNs were more likely to harbor high-grade dysplasia than polypoid neoplasms, regardless of size.1 A population-based study on colon cancers found that cancers in patients who had undergone a recent colonoscopy were more likely to have flat morphology than prevalent cancers.2

Optimizing Detection

Detection of flat neoplasia is a learned skill, requiring time and effort. Endoscopists who trained specifically in detection of NP-CRNs had initial low rates of detection following training, but improved significantly over time.3 Though few trials have specifically addressed techniques to optimize detection, the following recommendations are suggested:

  • An excellent bowel prep, with split dose: important all-around, but critical in the detection of NP-CRNs. In addition, several studies have found NP-CRNs to be predominantly located in the right colon, where suboptimal preps tend to be worse. In the case of fair preps, care should be given to thorough washing and suctioning.
  • Learn to recognize the features of NP- CRNs: these can include a red appearance and disruption in the vascular pattern and delicate grooves that line the colon. One great visual resource is ASGE’s learning video “Diagnosis of Flat and Depressed Colorectal Neoplasms.”4
  • Highlight the mucosa if needed: the application of diluted indigo carmine onto the surface where a nonpolypoid lesion is suspected can accent its presence and dramatically help to distinguish its borders. Mix one 5cc, vial of indigo carmine in 20ccs of water, place in a 50cc narrow-tipped syringe, and include an air column within the syringe. Then plunge the fluid into the working channel of the colonoscope.

Optimizing Removal

Small flat (but not depressed) adenomas under ~8 mm can typically be removed with cold snare, taking care to resect a rim of surrounding normal tissue so that resection is complete.

Endoscopic mucosal resection is the preferred resection method for larger or depressed NP- CRNs. In endoscopic mucosal resection, fluid is injected via an injection needle into the submucosa beneath the neoplasm, creating a bulge that lifts it up. The tissue is then hot snared. For an optimal lift, adjust the needle dynamically to bring the bulge high into the lumen, with the assistant injecting forcefully. Inject using a mixture of saline and indigo carmine (a few drops of indigo carmine mixed in 10mm saline) to outline the border of the NP-CRN, and use a stiff oval snare (such as the 10 and 20mm Olympus SD-210 and 230) to facilitate tissue capture. Use of blended cautery (ERBE Endo Cut Q) allows for cutting with minimal coagulation. Clips to close the resection defect are an option. Why endoscopic mucosal resection for these lesions? The method has at least two advantages to simple snaring. First, it creates a more “polypoid” form that allows the snare to grab the tissue; otherwise, the snare can slip over the flat neoplasm, a frustrating dilemma. Secondly, snaring a large NP-CRN without the heightened submucosal bulge runs the risk of grabbing too much tissue and resecting too deeply, posing the potential for perforation — either immediate or delayed, from extensive burn to the muscle.

NP-CRN: Improving our Understanding and Endoscopic Care

Flat and depressed colorectal neoplasms, or NP-CRNs, are known to be common worldwide and harbor more advanced pathology than their polypoid counterparts. They are possibly a key element to the missed and partially resected lesions that lead to interval cancer. Research is under way that will improve our understanding of the colon cancer risk associated with NP-CRNs. Even more importantly, gastroenterologists who train to detect and resect these lesions will find more of them and improve their patient care.

Dr. McGill has no conflicts to disclose.


1. Soetikno RM, Kaltenbach T, Rouse RV, et al. Prevalence of nonpolypoid (fl and depressed) colorectal neoplasms in asymptomatic and symptomatic adults. JAMA 2008;299:1027-35.

2. le Clercq CM, Bouwens MW, Rondagh EJ, et al. Postcolonoscopy colorectal cancers are preventable: a population-based study. Gut 2013.

3. McGill SK, Kaltenbach T, Friedland S, et al. The learning curve for detection of non-polypoid (fl and depressed) colorectal neoplasms. Gut 2013.

4. Soetikno R, Barro J, Friedland S, Matsui S, Rouse RV, Fujii T. Diagnosis of Flat and Depressed Colorectal Neoplasms. Learning video. 2004. American Society for Gastrointestinal Endoscopy. http://www.asge.org/ell_list. aspx. http://www.asge.org/ell_list.aspx: American Society for Gastrointestinal Endoscopy, 2004.

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