List of Abbreviations
CD
Crohn’s disease
CI
Confidence interval
CRC
Colorectal cancer
DALM
Dysplasia-associated lesion or mass
EMR
Endoscopic mucosal resection
ESD
Endoscopic submucosal dissection
HDWL
High-definition white light
HGD
High-grade dysplasia
IBD
Inflammatory bowel disease
IT
Isolation tipped
LGD
Low-grade dysplasia
NBI
Narrow-band imaging
NNT
Number needed to treat
OR
Odds ratio
RCT
Randomized controlled trial
SCENIC
The International Consensus Statement on Surveillance and Management of Dysplasia in Inflammatory Bowel Disease
SDWL
Standard-definition white light
UC
Ulcerative colitis
Introduction
Long-standing ulcerative colitis (UC) and Crohn’s colitis patients are at increased risk of colorectal cancer (CRC) and interval CRC. The risk of interval CRC is estimated to be 3 times higher in colitic inflammatory bowel disease (IBD) patients compared with non-IBD patients (odds ratio [OR] for UC, 3.05; 95% confidence interval [CI] 2.4–3.8; OR for Crohn’s colitis, 3.07; 95% CI 2.2–4.2). Nearly one half of all CRC diagnosed during IBD surveillance are attributed to interval CRC. This risk can be partially explained by dysplasia evading endoscopic detection, as it is often nonpolypoid (flat or depressed). Another explanation could be the failure of extensive random biopsy strategy, and the impairment of mucosal inspection using this technique.
Most CRC in IBD patients are believed to arise from dysplasia. Risk factors for developing colitis-associated dysplasia include longer extent and duration of disease, activity, and severity of inflammation, primary sclerosing cholangitis, family history of colorectal cancer, and colonic pseudopolyps or strictures ( Table 19.1 ). Hence, regular colonoscopic surveillance for the detection of dysplasia and early CRC is crucial.
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Surveillance Techniques
Limitations and failure of white-light colonoscopy in IBD surveillance has been highlighted for more than 2 decades. A metaanalysis of 10 prospective studies included 1225 patients with UC who underwent standard-definition white light (SDWL) colonoscopic surveillance. Forty patients had immediate colectomy after the diagnosis of dysplasia-associated lesion or mass (DALM). Cancer rates in biopsy proven high-grade dysplasia (HGD) and low-grade dysplasia (LGD) were 42% and 19%, respectively. In a US study of 55,000 Medicare patients diagnosed with colorectal cancer, IBD patients were 3 times more likely to have had a missed colorectal cancer after a recent colonoscopy than non-IBD patients. In a pooled analysis of 11 studies with 48,522 random biopsies from 1635 IBD patients, the number of detected dysplasia was only in 39 biopsies (0.08%).
Colonoscopic surveillance is challenging because of variability in endoscopic appearance and subtlety of dysplasia. In older fiberoptic and lower resolution endoscope systems, dysplasia was “invisible” as it was often discovered on random colonic biopsies. This was traditionally achieved by obtaining a minimum of 33 biopsies, by taking four-quadrant random biopsies every 10 cm in the colon, placed in separate containers, and taking more biopsies in the rectosigmoid colon. The limitations of white light with random biopsy in the detection of dysplasia, however, are many. The technique is inefficient, expensive, and inefficacious. It is estimated to only represent a colonic surface area <0.1%. Advancements in endoscopic technologies, such as high-definition resolution and enhanced contrast techniques, such as chromoendoscopy, have improved detection, characterization, and endoscopic management of colorectal neoplasia.
The majority of detected lesions are actually visible, well delineated, and potentially suitable for curative endoscopic resection. In 2004, a retrospective study of 525 patients long-standing UC who underwent SDWL surveillance colonoscopy with targeted biopsies of visible abnormal areas in addition to random biopsy showed almost 90% of dysplastic lesions were visible. Recognition of endoscopic features of dysplasia is pivotal for successful IBD surveillance colonoscopy. Features of dysplasia are subtle and difficult to appreciate. These features include slight elevation, focal friability, obscure vascular pattern, uneven redness, villous mucosa, or irregular nodularity ( Table 19.2 ).
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The SCENIC International Consensus
In 2015, the SCENIC International Consensus Statement on Surveillance and Management of Dysplasia in Inflammatory Bowel Disease (SCENIC) was developed by an international multidisciplinary expert panel and endorsed by multiple international gastrointestinal societies. This was an effort to determine the optimal method and standardize practice of surveillance and management of detected dysplasia in IBD. The SCENIC key recommendations for optimizing detection and management of dysplasia in IBD are:
- 1.
Using high-definition instead of standard-definition colonoscopes.
- 2.
Using chromoendoscopy with targeted biopsy is superior to white-light colonoscopy with random biopsy.
- 3.
Equipment-based chromoendoscopy (such as narrow-band imaging [NBI]) cannot replace dye-based chromoendoscopy.
- 4.
Using more accurate terminology for describing detected dysplasia as “endoscopically resectable” or “nonendoscopically resectable” and abandoning the use of “DALM,” “adenoma-like” and “non-adenoma-like.”
- 5.
Endoscopic removal of visible endoscopically resectable dysplasia rather than colectomy.
- 6.
After complete removal of endoscopically resectable polypoid dysplasia, surveillance colonoscopy is recommended rather than colectomy.
- 7.
After complete removal of endoscopically resectable nonpolypoid dysplasia, surveillance colonoscopy is suggested rather than colectomy.
- 8.
“Nonendoscopically resectable” dysplasia with indistinct borders confirmed by an endoscopist with expertise in IBD surveillance should be referred for surgery.
- 9.
Referral to an endoscopist with expertise in IBD surveillance using high-definition chromoendoscopy for patients with invisible dysplasia (confirmed by a GI pathologist).
Image-Enhanced Endoscopy
High-Definition White Light Is Superior to Standard-Definition White-Light Colonoscopy
High-definition (1080 system) endoscopy gives higher image details and improved resolution than the standard definition (480 system). High-definition white light (HDWL) colonoscopy improves colorectal neoplasia detection in IBD and non-IBD patients compared to SDWL colonoscopy. In a retrospective study comparing 209 HDWL colonoscopy and 160 SDWL in UC and Crohn’s disease patients, the adjusted prevalence for detecting any dysplasia or dysplasia on targeted biopsy was 2.21 (95% CI 1.09–4.45) and 2.99 (95% CI 1.16–7.79), respectively, in favor of HD colonoscopy. Experts recommend using HDWL colonoscopy rather than standard definition
Chromoendoscopy With Targeted Biopsy
Tada et al., first described chromoendoscopy using indigo carmine in 1976, where chromoendoscopy involves topical spraying of dye and stains to optimize detection and accurate real-time characterization of colonic mucosal lesions. The most widely used chromoendoscopic stains are indigo carmine and methylene blue. Indigo carmine is a contrast stain that is not absorbed by the colon. It highlights mucosal topography by pooling into crevices and grooves. Methylene blue is a vital stain that is transiently absorbed by normal colonic epithelium and is not absorbed by abnormal colonic epithelium caused by dysplasia or inflammation.
Chromoendoscopy Technique
Chromoendoscopy requires dyes and excellent bowel preparation for an effective technique. Excess water and debris are suctioned on scope insertion and prior to the application of dye. Diluted screening dye (indigo carmine 0.03%–0.1% or methylene blue 0.04%–0.1%) is applied on mucosal surface using applicators, such as syringes, foot pumps, or spray catheters segmentally starting at the caecum. To improve efficiency, the dye stream is sprayed onto the antigravity colonic surface to facilitate dye pooling. Once a colonic segment is completed, the scope is reinserted with collapsing the lumen to allow the dye to coat the entire lumen, and then excess dye is suctioned to allow mucosal inspection for dysplasia. Features of nonpolypoid dysplasia in IBD include mucosal surface unevenness (slight elevation or depression), focal friability, obscure vascular pattern, discoloration, villous, or nodular ( Table 19.2 ). Once a mucosal abnormality is detected, a more concentrated targeted dye (indigo carmine 0.13% or methylene blue 0.2%) may be sprayed through the working (biopsy) channel using a syringe to interrogate the lesion and delineate the margins to assess suitability of endoscopic resection.
Superiority of Chromoendoscopy With Targeted Biopsy
Chromoendoscopy with targeted biopsies increases the diagnostic yield for detecting colitis-associated neoplasia (six prospective and two randomized controlled trials) compared to white-light colonoscopy with random biopsies. In a metaanalysis of six clinical trials, chromoendoscopy with targeted biopsy had an incremental yield for detecting dysplasia by 7% per patient (95% CI 3.3%–10.3%) and the number needed-to-treat to find another patient with at least one dysplasia was 14.3 (range 9.7–30.3). Even in community practice, the yield of dysplasia detection is superior when using chromoendoscopy with targeted biopsies compared to white light with random biopsy. In a multicenter study of 900 patients undergoing chromoendoscopy with 4188 targeted biopsies detecting 8.3% patients with dysplasia (75 patients), the miss rate of dysplasia with additional 26,956 random biopsies was only 1% (9 patients). Another recent prospective multicenter study of 350 patients with 94 dysplastic lesions, the dysplasia detection incremental yield was 57.4% for chromoendoscopy with targeted biopsies over white light with random biopsies. The use of chromoendoscopy in IBD surveillance has been endorsed by gastrointestinal societies. The presence of strictures and pseudopolyps in IBD can limit the utility of chromoendoscopy with targeted biopsies. In such circumstances, random biopsy technique can be used, as strictures can often harbor malignancy. Despite the overwhelming evidence recommending colonoscopic surveillance using chromoendoscopy with targeted biopsy, widespread clinical implementation remains challenging.
Morphologic Description and Endoscopic Characterization of Inflammatory Bowel Disease Dysplasia
SCENIC proposed a new morphologic description, modified from the Paris classification, in an effort to unify terminology and standardize communication ( Table 19.3 ). It clearly defines the term endoscopically resectable as a lesion with identifiable distinct margins, appears to be completely removed on visual inspection after endoscopic resection, completely removed on histologic examination and is dysplasia free on confirmatory biopsies from mucosa immediately adjacent to the resection margin. This is in contrast to the previous confusing terminology such as DALM, adenoma-like and non-adenoma-like .
| Definition | |||
|---|---|---|---|
| Visible dysplasia | Dysplasia identified on targeted biopsies from a lesion visualized at colonoscopy | ||
| Polypoid | Lesion protruding from the mucosa into the lumen ≥2.5 mm | ||
| Pedunculated | Lesion attached to the mucosa by a stalk | ||
| Sessile | Lesion not attached to the mucosa by a stalk: entire base is contiguous with the mucosa | ||
| Nonpolypoid | Lesion with little (<2.5 mm) or no protrusion above the mucosa | ||
| Superficial elevated | Lesion with protrusion but <2.5 mm above the lumen (less than the height of the closed cup of a biopsy forceps) | ||
| Flat | Lesion without protrusion above the mucosa | ||
| Depressed | Lesion with at least a portion depressed below the level of the mucosa | ||
| General descriptors | Ulcerated | Ulceration (fibrinous-appearing base with depth) within the lesion | |
| Border | Distinct border | Lesion’s border is discrete and can be distinguished from surrounding mucosa | |
| Indistinct border | Lesion’s border is not discrete and cannot be distinguished from surrounding mucosa | ||
| Invisible dysplasia | Dysplasia identified on random (nontargeted) biopsies of colon mucosa without a visible lesion | ||
Related posts:
Classification and Reclassification of Inflammatory Bowel Diseases: From Clinical Perspective
Preparation of Endoscopic Therapy for Inflammatory Bowel Diseases
Principles of Endoscopic Therapy in Inflammatory Bowel Diseases
Endoscopic Management of Hepatobiliary Complications of Inflammatory Bowel Disease
Fecal Microbiota Transplantation as Therapy for Inflammatory Bowel Disease
Common Complications of Surgery for Crohn’s Disease and Ulcerative Colitis
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