Endoscopic Detection and Removal of Colitis-Associated Dysplasia

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.

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 ).

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