10.1055/a-1120-8376Patients with ulcerative colitis (UC) or Crohn’s colitis have an increased risk of
colorectal cancer compared with the general population. Because colitis-associated
dysplasia is often subtle, flat or not endoscopically identifiable, the first surveillance
guidelines recommended sampling four random biopsies from every 10 cm of colon in
addition performing targeted biopsies of lesions suspected of containing dysplasia
[1].
In earlier endoscopic eras, most dysplasia was “invisible” and discovered on random
biopsy samples, but today, most dysplasia detected at surveillance colonoscopy is
visible. Recent progress in endoscopic technologies, such as high-definition video
endoscopy, and use of image enhancement methods such as chromoendoscopy, seem to explain
the increased proportion of visible dysplastic lesions identified at surveillance
colonoscopy [2].
In this issue of Endoscopy International Open, Ricardo et al report on a systemic
review and meta-analysis of randomized controlled trials (RCTs) comparing various
surveillance techniques [3]. The authors reviewed 17 RCTs totaling 2,457 patients. The evaluated outcomes were
number of patients diagnosed with one or more dysplastic lesions, total number of
dysplastic lesions detected, number of dysplastic lesions detected by directed biopsies,
and procedure time. The authors found that dye-spraying chromoendoscopy detected more
patients and dysplastic lesions than standard-definition white-light endoscopy (WLE).
Although no difference was observed between dye-spraying chromoendoscopy and high-definition
WLE or narrow-band imaging, the main outcomes favored numerically dye-spraying chromoendoscopy,
except procedure time.
Chromoendoscopy, also known as dye-based image enhancement, using a dye solution of
either methylene blue or indigo carmine applied onto the colonic mucosa to enhance
contrast during surveillance colonoscopy, is generally performed either in a pancolonic
fashion to detect lesions or a targeted fashion to allow for detailed viewing of an
identified lesion. These agents are applied to the entire colonic mucosa with a spray
catheter or the water jet channel of a standard colonoscope. The Surveillance for
Colorectal Endoscopic Neoplasia Detection and Management in inflammatory Bowel Disease
Patients: International Consensus Recommendations (SCENIC-ICS) consensus reinforces
the placement of panchromoendoscopy as the preferred technique for surveillance of
dysplasia in inflammatory bowel disease (IBD) [4]. Accordingly, many Western scientific societies, such as the British Society of
Gastroenterology and European Crohn’s and Colitis organization, recommend use of panchromoendoscopy
with targeted biopsies for IBD-colorectal cancer surveillance.
Despite these results and recommendations, panchromoendoscopy is not routinely used
for IBD-colorectal cancer surveillance. This protocol carries additional costs for
the equipment needed for dye spraying, and it is time consuming and requires an endoscopist
who is familiar with the technique. Furthermore, some patients are not considered
as candidates for chromoendoscopy because of inadequate bowel preparation or significant
visible inflammation. Presence of active mucosal inflammation or post-inflammatory
polyps may affect the images and procedures of chromoendoscopy. Mucosal healing may
improve identification of dysplasia. Bowel preparation should be excellent to allow
for detailed mucosal evaluation. Barriers to adoption of chromoendoscopy also include
patient adherence. Historic data on patient adherence to colitis surveillance programs
suggest that about half of patients drop out, negating the efficacy of surveillance.
Most studies demonstrating the superiority of chromoendoscopy over WLE with standard-definition
colonoscopies had been done before the studies evaluating characterization of morphological
features of dysplasia detected by high-definition WLE. Recently, several reports have
been published about accurate endoscopic characterization of dysplasia. Sugimoto et
al classified for the first time the morphological features of high-grade dysplasia
using the SCENIC consensus [5]. The authors detected all lesions by targeted biopsy sampling without panchromoendoscopy
and found that high-grade dysplasia is frequently associated with a flat/superficial
elevated area and red discoloration. The authors performed regular white-light colonoscopy,
followed by 0.2 % to 0.4 % indigo-carmine dye spraying after suspected lesions were
recognized. Iacucci et al have developed, validated, and reproduced a new endoscopic
classification (FACILE; Frankfurt Advanced Chromoendoscopic Ibd LEsions) using all
imaging modalities for diagnosis of dysplasia in IBD [6]. Flat shape, irregular surface, vascular pattern, and signs of inflammation predicted
dysplasia.
A recent meta-analysis of 10 studies (494 patients) compared dye-based chromoendoscopy
with standard-definition WLE and high-definition WLE [7]. RCTs in the literature showed a small benefit of chromoendoscopy over standard-definition
WLE, but not over high-definition WLE. New and advanced endoscopic technologies, such
as increased resolution of high-definition endoscope, significantly improved resolution
of the images compared to conventional WLE, as dysplasia became easier to see from
the greater detail of the images [8]. When assessing the comparative network analysis, we must keep in mind that inclusion
of studies published in the first decade of the 2000 s could be biased by use of the
previous generation of endoscopes with standard WLE.
In Japan, there is no concrete consensus on management of colitis-associated neoplasia.
According to the discussion on the basis of a questionnaire survey completed by nine
Japanese expert panelists from high-volume centers for patients with UC, WLE used
high definition as the main observation method of surveillance colonoscopy [9]. Recently Watanabe et al reported that results of a trial of patients with UC who
were randomized to surveillance colonoscopy showed that targeted biopsy is as effective
as a random biopsy for detection of neoplasia in UC [10]. This study was performed in 52 Japanese institutions. As discussed in the literature,
panchromoendoscopy is not generally used in surveillance colonoscopy in Japan. Chromoendoscopy
is generally performed in a targeted fashion to allow for detailed viewing of an identified
lesion. In the authors’ institution, high-magnification colonoscopy with indigo carmine
chromoendoscopy is routinely performed after they suspect presence of dysplasia in
patients with IBD. Morphologically, dysplasia in IBD appears to be slightly elevated,
completely flat, or slightly depressed as compared with the surrounding mucosa. To
detect it, the authors look for presence of a slightly elevated lesion, focal friability,
obscure vascular pattern, discoloration (uneven redness or a patch or redness), villous
mucosa (velvety appearance), and irregular nodularity. Examination with varying expansion
of the colon (after increasing and decreasing air insufflation) also improves visualization
of the subtle-appearing flat and depressed neoplasms. Once a suspicious lesion is
identified, the mucosal surface is washed with a detergent to remove mucus and bubbles
before detailed observation. Then approximately 0.4 % of indigo carmine dye is sprayed
directly from a 60-mL syringe through the biopsy channel. In our experience, we realized
that some dysplasia found by chromoendoscopy could be identified with high-definition
WLE by careful observation of subtle color differences or mild friability. Chromoendoscopy
is used for characterization of the detected lesions found by WLE.
A novel endoscopic system and colonoscope with a dual-focus function has recently
become available in Western countries. This enables dual-focus near-field magnification
by pushing a single button to closely examine the surface structure and capillary
network of the mucosa. Nishiyama et al reported that chromoendoscopy with a magnifying
endoscope is useful for differentiating between neoplastic and non-neoplastic lesions
by assessing the high residual density of pits and irregular pit margins under magnification
[11].
Although we still do not have the perfect method, techniques for defining the mucosa
in detail during endoscopy are rapidly evolving with various new endoscopic systems.
The search for a gold standard method for colon cancer surveillance in patients with
IBD continues with the goal of identifying one that can be widely used.
