Improving protection against proximal colon cancer by colonoscopy

Abstract

Colonoscopy protection against proximal cancer can be achieved, but the level of protection has thus far been less than left colon protection. Improved proximal protection begins with effective right colon bowel preparation, best achieved by split dosing the preparation regimen. Cecal intubation in screening examinations should exceed 95%, and must be documented by photography. Examiners must be proficient in detection of subtle right colon lesions, including serrated lesions as well as flat and depressed adenomas. Effective examination should be demonstrated by meeting recommended targets for adenoma detection.

Keywords::

• bowel preparation
• colonoscopy
• colorectal cancer
• flat and depressed
• lesions
• polypectomy
• serrated polyps

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Release date: October 24, 2011; Expiration date: October 24, 2012

Learning objectives

• • Evaluate colonoscopy in improving outcomes associated with proximal colon cancer

• • Analyze the best methods for administering preparations for colonoscopy

• • Distinguish polyps particularly found in the proximal colon

• • Assess colonoscopic techniques that can improve the detection of lesions in the proximal colon

Financial & competing interests disclosure

EDITOR

Elisa Manzotti,Editorial Director, Future Science Group, London, UK

Disclosure:Elisa Manzotti has disclosed no relevant financial relationships.

CME AUTHOR

Charles P Vega, MD,Health Sciences Clinical Professor; Residency Director, Department of Family Medicine, University of California, Irvine, CA, USA

Disclosure:Charles P Vega has disclosed no relevant financial relationships.

AUTHORS

Femi Lasisi,Indiana University Hospital, #4100, 550 N University Boulevard, Indianapolis, IN, 46202, USA

Disclosure:Femi Lasisi has disclosed no relevant financial relationships.

Douglas K Rex,Indiana University Hospital, #4100, 550 N University Boulevard, Indianapolis, IN, 46202, USA

Disclosure:Douglas K Rex has disclosed no relevant financial relationships.

Figure 1. The Paris classification for shape of colorectal polyps and flat lesions.

Dotted lines represent 2.5 mm of elevation above the normal mucosal surface.

Figure 2. Endoscopic photographs of serrated lesions in the colon.

(A) White light photograph of two serrated lesions in the transverse colon. Note the mucus covering on the lesions. The color is similar to the surrounding mucosa, and the lesion obscures the vascular pattern of the normal colon. (B) Narrow-band imaging photograph of a serrated lesion. The mucus cap has a pink colon.

Figure 3. Photodocumentation of the right colon.

(A) Appendiceal orfice. (B) Ileocecal valve. (C) Terminal ileum. (D) Ascending colon in retroflexion.

Early studies evaluating the impact of colonoscopy on colorectal cancer demonstrated a range of benefits [1–5], but did not distinguish between the impact of colonoscopy on proximal versus distal cancer. Early proponents of converting colonoscopy from a diagnostic and surveillance procedure to a screening procedure assumed that the benefits of sigmoidoscopy on distal colon cancer [6–9] could be extrapolated to the proximal colon. Therefore, the appearance of studies from two centers in Canada showing a substantial benefit from colonoscopy and protection against distal colon cancer but little protection against proximal colon cancer [10–13] were met with shock and incredulity, particularly in the USA. Some of the earliest proponents of screening colonoscopy opined that had they seen this information, they would not have recommended the development of screening colonoscopy [14]. Editorials in major US newspapers suggested to patients that they would be just as well off to undergo screening by sigmoidoscopy as by colonoscopy [15].

However, subsequent studies have clarified the situation in Canada and indicated that proximal colon protection does occur when colonoscopy is performed well. Colonoscopy by gastroenterologists in Manitoba, Canada, was associated with a 39% reduction in proximal colon cancer mortality, but there was no reduction when colonoscopies were performed by physicians in other specialties [13]. There was a significantly (59%) lower risk of proximal colon cancer mortality after colonoscopy by gastroenterologists when only negative colonoscopies were considered and, again, no lower risk of proximal colon cancer after negative colonoscopy performed by other specialists [13]. A previous report from Ontario, Canada showed that patients of general surgeons had a higher overall risk of colorectal cancer after colonoscopy compared with patients of gastroenterologists [16]. In a very recent study, proximal colon cancer protection in Ontario was shown to be operator dependent, with patients of doctors who were neither gastroenterologists or surgeons having a higher risk of developing proximal colon cancer after colonoscopy [17]. Thus, the Canadian studies have now been clarified to indicate that there is an operator-dependent protection against proximal colon cancer. Similarly, two German case–control studies from the same group have shown a 56–60% reduction in proximal colon cancer after colonoscopy performed almost entirely by gastroenterologists [18,19]. A study presented at Digestive Disease Week 2007 from the USA, in which the risk of proximal and distal colon cancer was described in California Medical patients, showed an 84% reduction in distal colon cancer in both genders and a 62% reduction in proximal colon cancer for men and a 19% reduction for women after colonoscopy [20]. These studies provide additional evidence that proximal colon cancer protection is achievable. However, all of these studies have shown greater reductions in distal colon cancer than proximal cancer. Therefore, proximal colon cancer protection after colonoscopy is operator dependent and in general, proximal colon cancer protection is more difficult to achieve than distal colon cancer protection.

Operator factors affecting right colon protection

The principal evidence that training in colonoscopy affects right colon cancer protection is that gastroenterologists have had consistently better right colon cancer protection (and cancer protection in general) than endoscopists in other specialties (Box 1)[11,13,21]. The elements of training in gastroenterology fellowship programs that distinguish colonoscopic performance are as yet not clear. Indeed, the difference in protection between gastroenterologists and other specialists can only be considered indirect evidence that training is the underlying factor, since other elements could underlie the differences. The withdrawal techniques associated with high-level detection have been studied by video recording and include taking adequate time, meticulous inspection of the proximal sides of haustral folds, adequate cleaning of retained debris and suctioning of retained fluid, and adequate lumenal distention [22–24]. These elements should form the basis of teaching colonoscope manipulation during withdrawal, but they may not ensure lesion recognition.

Recent data from Ontario identify two specific colonoscopic factors that are directly applicable to the continuous quality-improvement program in colonoscopy that are associated with proximal colon cancer reduction after colonoscopy. Thus, Baxter et al. found that patients colonoscoped by doctors with polypectomy rates of 25–29% and ≥30% had 52 and 39% lower incidence rates, respectively, of subsequent proximal colon cancers when compared with the patients of doctors with polypectomy rates <10% [17]. A previous study of screening colonoscopy in Poland found that the adenoma detection rate (ADR) was a powerful predictor of subsequent risk of colorectal cancer [25], but there were too few cancers to distinguish whether the ADR predicted protection against both proximal and distal cancers. The Ontario study also provided evidence that cecal intubation predicts proximal colon cancer protection. Patients colonoscoped by doctors with cecal intubation rates of 90–94% and ≥95% had 34 and 28% lower incidence rates of proximal cancer, respectively, compared with doctors with cecal intubation rates below 80% [17].

Given that differences in training between specialists are hard to immediately correct, the current evidence suggests that measurement of the ADR and cecal intubation rates are the best validated quality targets for endoscopists of any specialty to improve proximal colon cancer protection.

Other factors contributing to poor right colon protection

There are several additional factors that are relatively specific to right colon protection and which are also at least partly under the control of the operator (Box 1). The first factor, and the easiest to correct, is bowel preparation. Bowel preparation has traditionally been worse in the cecum and ascending colon compared with the distal colon, and many clinical trials specifically report ascending colon cleansing scores. The reason why proximal colon cleansing has been traditionally more difficult to achieve than distal colon cleansing is because after stool is cleared from the colon, mucus and chyme are released from the small intestine and tend to stick to the cecum and right colon. This problem can be overcome by either ‘split dosing,’ in which half of the preparation is given on the day of the examination, or same-day dosing of the entire preparation. A total of ten different randomized controlled trials have compared split dosing to traditional evening-before dosing, and all ten showed improved cleansing efficacy with split dosing, particularly in the ascending colon [26–35]. In addition, there is a strong trend in these trials for tolerability to be improved by split dosing [26–35]. It is conceivable that split-dose preparations are even safer than evening-before dosing, because electrolyte disturbances induced by the preparation might be less likely to become severe when there is expansion of the amount of time over which the preparation is ingested. Ingestion of the second half of the preparation close in time to when the colonoscopy is performed clears mucus and chyme from the colon and makes proximal colon cleansing as effective as distal colon cleansing. Effective proximal colon cleansing may be particularly important because two sets of mucosal lesions that are endoscopically subtle are preferentially distributed in the proximal colon. The first are the so-called ‘flat and depressed’ lesions [36] (also called nonpolypoid colorectal neoplasia) and the second are serrated lesions.

Recent studies have found that patients with afternoon colonoscopies can ingest the entire preparation on the day of the examination [37]. It is unknown whether this leads to better tolerability but it has been shown to result in less work disruption on the day prior to colonoscopy [37]. Split dosing or same-day dosing is particularly important for afternoon colonoscopies and may be less important for colonoscopies performed first thing in the morning. If patients are unwilling to get up in the middle of the night to take their second dose of preparation, then patients scheduled very early in the morning will typically have adequate preparations if they ingest the second dose quite late the night before. Right colon preparation begins to deteriorate several hours after completion of the ingestion but generally maintains quite good quality for at least 6–8 h. After that, average preparation of the proximal colon is deteriorating hour by hour. In our experience, 80% of patients are willing to get up in the middle of the night to take the second half of the preparation, and often keep a preference for early-morning appointments, even when told about the need to get up during the night [38]. We ask patients to begin the second dose of the preparation 4–5 h before the time they are scheduled and to complete the preparation by at least 3 h prior to the time of colonoscopy. Another concern sometimes expressed about split dosing and same-day dosing is that patients will not have been nil per os since midnight or for 8 h prior to the procedure. However, the guideline from the American Society of Anesthesiologists on fasting prior to sedation and anesthesia indicates that patients can take clear liquids until 2 h prior to the administration of sedation [39]. This recommendation is based on studies showing that residual gastric volumes are unaffected by the time at which patients stop drinking clear liquids, provided that they have been nil per os for 2 h prior to the procedure [39,40].

The other two factors that are relatively specific to the proximal colon are the distribution of flat and depressed as well as serrated lesions, as noted previously. Compared with polypoid neoplasia, both flat and depressed lesions [41] and serrated lesions can be endoscopically very subtle [42,43]. Education of endoscopists is important to develop a clear understanding of the endoscopic appearance of these lesions and for endoscopists to develop ‘an eye’ for their detection.

Polyp shape is currently designated by the Paris classification [44]. In this classification, Type 1 lesions are traditional polyps, shaped as either pedunculated (1p) or sessile (1s). Type 1 lesions are designated as ‘nonpolypoid colorectal neoplasia’ (Figure 1). The flat lesions are Type 2a and 2b. Type 2a lesions are actually elevated lesions that are distinguished from sessile lesions in the Paris classification because they project into the lumen less than the width of a standard biopsy forceps (2.5 mm). Flat 2a lesions and sessile 1s lesions collectively constitute more than 90% of colorectal lesions [45]. The histology of 2a lesions is quite similar to that of Type 1 lesions; for instance, there is a very low incidence of high-grade dysplasia and invasive cancer [36].

The most worrisome Type 2 lesions are designated 2c and variants of 2c in the Paris classification. Collectively, the 2c lesions are referred to as ‘depressed.’ The depression in 2c lesions is typically characterized by a relatively sharp drop-off from the elevated portion of the lesion to the depressed portion. Furthermore, the depression typically occupies a substantial fraction of the surface area of the lesion. Type 2c lesions have a dramatically increased risk of invasive cancer and high-grade dysplasia [36,41], but they are also very uncommon. A true 2c lesion probably occurs in approximately one in every 800 screening colonoscopies in Western populations [36,41]. These lesions are more common in symptomatic patients than patients undergoing surveillance for prior cancer and adenomas. Flat lesions can be recognized endoscopically by slight changes in the color and surface texture of the polyp surface compared with the normal colonic mucosa and because they disrupt the normal colonic vascular pattern. Once the typical appearance of flat and depressed lesions is understood by the endoscopist, constant vigilance is needed to maximize their detection. Huge numbers of diminutive 2a lesions are detected during screening colonoscopy by high-level detectors using high-definition colonoscopes [45–47]. These detectors have redefined the true prevalence of adenomas during screening colonoscopy to be in the vicinity of 50%. However, the significance of detection of large numbers of these diminutive flat lesions is uncertain, and there is currently no consensus that recommended ADR [48,49] should be moved upward to reflect the new true prevalence of adenomas as defined by high-definition colonoscopy.

There is some disagreement as to whether the ADR is the best measure of detection performance. Advantages of the ADR include its prospective validation as a predictor of interval cancer [25], and its relatively limited susceptibility to gaming [50]. However, measurement usually requires manual entry of pathology reports into databases, because endoscopy and pathology databases currently rarely communicate [50]. Adenoma detection correlates strongly with overall polyp detection when examined retrospectively, and the polyp detection rate (PDR) is easier to measure [51]. The PDR can be considered an alternative to the ADR when resources to measure ADR are lacking. Potential downsides to the PDR include some uncertainty regarding best targets, lack of prospective study or validation, and probably a relatively higher risk of gaming from removal of obvious diminutive rectosigmoid hyperplastic polyps or even normal tissue [50].

The WHO recommends that serrated lesions be classified as hyperplastic polyps, sessile serrated adenomas/polyps (SSA/Ps) (with or without cytologic dysplasia), and traditional serrated adenomas (TSAs) [52]. However, both the classification of serrated lesions and the pathologic definitions of the specific types of lesions remain controversial [53,54]. TSAs are the least common of the serrated lesions, tend to be bulky and occasionally even pedunculated, and distributed toward the left colon. TSAs are clearly precancerous, but with regard to improving right-sided cancer protection, the most important lesions are the SSA/Ps (Table 1). ‘Sessile serrated adenoma’ and ‘sessile serrated polyp’ are considered synonyms. At least two-thirds of SSA/Ps are located in the proximal colon [42,55,56]. Their shape is typically sessile or flat. Several endoscopic features distinguish them from adenomas, including the typical ‘mucus cap’ on their surface, a tendency toward vaguely defined borders, the subtle variegated appearance of their surface, and the paucity of blood vessels on the surface when viewed in high-definition white light or with electronic vessel-highlighting techniques such as narrow-band imaging (Figure 2)[42,43]. Many SSA/Ps have a 2a shape. Occasional SSA/Ps have cytologic dysplasia and the areas of dysplastic mucosa in these lesions often have microsatellite instability [52]. The SSA/P with cytologic dysplasia is considered a more advanced lesion than SSA/P and represents progression in the serrated lesion to cancer sequence. It is unclear whether hyperplastic polyps are precursors of SSA/Ps or whether the two groups of serrated lesions arise independently. However, there is a generally accepted cancer hypothesis of a hyperplastic polyp to sessile serrated adenoma to cancer sequence.

Indirect evidence suggests that undetected serrated lesions at colonoscopy are a major contributor to the problem of cancers that develop after colonoscopy, or so-called interval cancers [57]. Specifically, interval cancers are more likely to be in the proximal colon, are more likely to be microsatellite unstable, and to have the CpG island methylator phenotype (CIMP). CIMP refers to a pattern of gene hypermethylation that is characteristic of a substantial subgroup of colorectal cancers. CIMP-positive tumors also usually carry mutations in the BRAF oncogene. BRAF is an oncogene that participates in a signaling pathway at a position immediately downstream from KRAS. Most colorectal cancers arise through a molecular pathway designated the chromosomal instability pathway, are usually CIMP-negative and often carry KRAS mutations. Tumors in the CIMP pathway are almost universally mutated in BRAF and almost never have KRAS mutations. SSA/Ps also frequently demonstrate CIMP and BRAF[58–62]. Over-representation of CIMP and MSI in interval cancers provides the rationale for emphasizing detection of serrated lesions in the proximal colon during colonoscopy.

Atlases of serrated lesions are available for colonoscopists [63]. Constant vigilance for serrated lesions is essential and all small patches of adherent mucus in the proximal colon should be investigated, although experienced endoscopists quickly learn to differentiate retained mucus not associated with polyps from the mucus cap of serrated lesions. Serrated lesions should be sought out and resected fully. The optimal means of resection has not yet been established but there is anecdotal evidence to indicate that the postpolypectomy bleeding rate is less after resection of serrated lesions than after adenomas [Church J, Pers. Comm.], and there is no evidence that the complication rate is higher after serrated lesion resection. Lesions resected piecemeal may warrant close endoscopic follow-up in a few months, similar to that used for resection of adenomatous lateral-spreading tumors. Recent studies investigating variable detection of serrated lesions have identified nearly 20-fold differences in detection of proximal colon serrated lesions between experienced colonoscopists in the same endoscopy group [42,43]. This suggests that some endoscopists are missing most of the serrated lesions in the proximal colon.

Potential technical solutions to poor right colon detection

Box 2 divides technical measures that might improve right colon lesion detection during colonoscopy into three groups, including general measures, measures to improve mucosal exposure, and measures to improve the detection of flat and subtle lesions. The evidence that training impacts on right colon protection suggests that current training in many general surgery, primary care, and perhaps even some gastroenterology programs, is inadequate. The elements of good training may include colonoscopic techniques to increase mucosal exposure on the front sides of folds, instruction in measurement of ADR, education about the appearance of subtle endoscopic lesions, transmittance of techniques to ensure high cecal intubation, and so on. The exact elements of training that optimize right colon protection are still uncertain.

Some measures that have been developed for improving right colon mucosal exposure are listed in Box 2. In examining the right colon twice, it might be useful to perform the second examination in retroflexion [64]. Both adult and standard colonoscopes can be placed into retroflexion in the proximal ascending colon and are withdrawn in retroflexion to the hepatic flexure. There is currently no evidence that a second examination performed in retroflexion is superior to a second examination performed in the forward view [65]. In a series of 1000 consecutive patients undergoing primarily screening and surveillance colonoscopy, a second examination in retroflexion after removal of all lesions detected in the forward view identified a miss rate for the first examination of 9% for all polyps, and five lesions 1 cm or larger were identified in retroflexion [64]. The performance of right colon retroflexion appears safe and can be very helpful, if not essential, for the resection of some right colon polyps located on the proximal sides of folds [66].

The Third Eye^® Retroscope^® (Avantis Medical Systems) is an ancillary colonoscopy device that is passed down the working channel of the colonoscope, where it automatically retroflexes and provides a second retroflexed image that is viewed side by side with a forward-viewing image from the colonoscope. Initial studies suggested that the device produces slightly greater gains in the right colon than it does in the left colon [67]. Therefore, the Third Eye Retroscope could be a useful approach to improving right colon detection. Cap-fitted colonoscopy refers to placing a hood or cap on the tip of the colonoscope, which is used to flatten folds and see the proximal side mucosa better. Asian studies have had mixed results with regard to improved adenoma detection, and a single tandem study from the USA showed improved detection with the cap, although it was not clear that there was special benefit in the proximal colon [68]. A principle advantage of the cap compared with the Third Eye Retroscope is that it is considerably less expensive and does not need to be removed in order to perform therapeutic procedures.

Wide-angle colonoscopy has been studied several times and generally does not produce a benefit in lesion detection, at least in the hands of high-level detectors [69].

Techniques for improving detection of flat lesions have not generally been evaluated for a specific right colon benefit or specifically for the detection of proximal colon serrated lesions. These issues deserve further evaluation. Chromoendoscopy has generally been effective in improving the yield of small flat adenomas, and the most practical development that appears to influence adenoma detection is high-definition optics [69]. Narrow-Band Imaging (Olympus Corp.), the Fujinon Intelligent Chromoendoscopy System™ (Fujinon) and autofluorescence (Olympus Corp.) have generally been ineffective for improving adenoma detection [69], although evaluation of these technologies for detection of serrated lesions in the proximal colon is warranted. The iSCAN System (Pentax) did improve adenoma detection [70], but published experience has been limited to one center.

Expert commentary

Effective examination begins with effective preparation, and consistent preparation requires split dose or same-day dosing of bowel preparations. All currently used bowel preparations can be split.

Next, cecal intubation must be complete, with the scope tip fully penetrating the cecal caput, so that the appendiceal orifice is visualized, and the mucosa between the appendiceal orifice and the ileocecal valve inspected. Cecal intubation must be documented by notation of landmarks and by photography (Figure 3). The most important photograph is that of the appendiceal orifice, taken from a sufficient distance to show the triangulation of tinea around the appendix, or the so-called cecal strap fold. The terminal ileum should be photographed if intubated, and the cecum should also be photographed from just distal to the ileocecal valve.

Next, examination technique must be meticulous in the right colon, by an examiner who is trained in the detection of flat and depressed lesions and also serrated lesions. Slow careful inspection of the mucosa, with probing of the proximal sides of haustral folds, is essential. The interhaustral valleys are sometimes quite deep in the right colon, and the colonoscope tip should be deflected carefully between each set of haustral folds in all sectors of the colon. The proximal colon examination should be slow and meticulous. Consideration can be given to retroflexion or to a second forward examination. Additional examination, or repeat examination, is especially appropriate when the forward view has identified multiple ascending colon polyps. After detection, all lesions should be fully resected. Most importantly, effective protection against cancer throughout the colon involves measurement of the ADR. In the future, we may see recommendations for a proximal colon serrated PDR. However, it is not yet clear that a separate serrated lesion is needed because adenoma detection and serrated lesion detection are strongly correlated. Pending definitive studies, these recommendations should help to maximize the level of right colon protection afforded by colonoscopy.

Five-year view

Split-dose bowel preparations should become standard of care. New investigation will continue to focus on maximizing safety and tolerability of bowel preparations. The components of training that result in optimal examination technique must be determined and disseminated. Education gaps in the recognition of serrated lesions and flat and depressed lesions should be closed. Quality measurements of cecal intubation and adenoma detection will become widespread and preferably mandated. New studies should evaluate whether detection technologies have specific benefits in the right colon, including benefits for overall right colon protection, and detection of serrated lesions and flat and depressed lesions.

Table 1. Distribution of colorectal mucosal lesions by histology and shape.

Histology	Shape (Paris)	Predominant location
Adenoma	Pedunculated (1p) Sessile (1s) Flat (2a) Depressed (2c)	Left colon Throughout colon Right colon Right colon
Serrated lesion: Hyperplastic SSA/P TSA	1s and 2a 1s and 2a 1s and 1p	Left colon Right colon Left colon

SSA/P: Sessile serrated adenomas/polyp; TSA: Traditional serrated adenoma.

Box 1. Contributors to impaired right colon protection by colonoscopy.

• • Inadequate training

• • Low cecal intubation rate

• • Low polypectomy rate

• • Inadequate bowel preparation

• • Failed detection of endoscopically subtle lesions:

  • – Serrated lesions

  • – Flat and depressed lesions

Box 2. Potential technical solutions to poor right colon detection.

General measures

• • Training in fold exploration

• • Specified right colon withdrawal time

• • Examine right colon twice

Improved mucosal exposure

• • Examine right colon in forward and retroflexed view

• • Third Eye^® Retroscope^® (Avantis Medical Systems)

• • Cap-fitted colonoscopy

• • Wide-angle colonoscopy

Improved detection of flat lesions

• • Chromoendoscopy

• • High definition

• • Narrow-Band Imaging (Olympus Corp.)

• • Fujinon Intelligent Chromoendoscopy™ (Fujinon)

• • iSCAN (Penxtax)

• • Autofluorescence (Olympus Corp.)

Key issues

• • Proximal colon cancer protection by colonoscopy occurs, but is operator-dependent.

• • Proximal cancer protection by colonoscopy is more difficult to achieve than distal cancer protection.

• • Bowel preparation tends to be worse in the cecum and ascending colons, but this can be corrected by ‘split dosing’ of preparations.

• • All bowel preparations can be split. Patients who understand the value of splitting and who have early morning appointments are generally willing to get up in the night and take the second dose. Splitting is compatible with American Society of Anesthesiologists guideline on fasting prior to sedation.

• • Sessile serrated adenomas (polyps), flat adenomas and depressed lesions are all distributed toward the proximal colon and all are more difficult to detect endoscopically than traditional adenomatous polyps.

• • Serrated lesions are present in the proximal colon in up to 20% of screening colonoscopies. They are often flat, typically identical in color to the normal mucosa, have indistinct edges, and can be recognized by the typical ‘mucus cap’ and the disruption of the normal colonic vascular pattern.

• • Sessile serrated adenomas account for a disproportionate percentage of missed cancers in the proximal colon, as evidenced by their molecular features, which are similar to the preponderance of interval cancers, including BRAF mutations and the CpG island methylator phenotype.

• • Potential techniques to improve right colon mucosal exposure during colonoscopy include right colon retroflexion, cap-fitted colonoscopy and the Third Eye^® Retroscope^®. Cap-fitted appears to be the best combination of being effective and easy to use.

• • Highlighting technologies such as chromoendoscopy, Narrow-Band Imaging, autofluorescence, the Fujinon Intelligent Chromoendoscopy System, and iSCAN have not generally been evaluated for their potential to improve detection of serrated and depressed lesions.

Financial & competing interests disclosure

Douglas K Rex has received speaker’s bureau and research support from Olympus. The authors have no other relevant affiliations or financial involvement with any organization or entity with a financial interest in or financial conflict with the subject matter or materials discussed in the manuscript apart from those disclosed.

No writing assistance was utilized in the production of this manuscript.

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Improving protection against proximal colon cancer by colonoscopy

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Activity Evaluation: Where 1 is strongly disagree and 5 is strongly agree

	1	2	3	4	5
1. The activity supported the learning objectives.
2. The material was organized clearly for learning to occur.
3. The content learned from this activity will impact my practice.
4. The activity was presented objectively and free of commercial bias.

1. A 50-year-old woman presents at average risk for colorectal cancer. You discuss colon cancer screening options with her. What should you consider regarding the detection of proximal colon cancer?

• □ A Colonoscopy has not been demonstrated to improve mortality due to proximal colon cancer

• □ B The number of polypectomies performed has no effect on the incidence of proximal colon cancer

• □ C Of the physicians performing colonoscopy, gastroenterologists appear most effective in reducing proximal colon cancer mortality

• □ D Women benefit from screening for proximal colon cancer more than men

2. The patient elects to have a screening colonoscopy. What should you consider when prescribing her the preparation for this procedure?

• □ A Split dosing of the preparation improves the cleansing of the proximal colon

• □ B The preparation cannot be consumed safely on the day of the procedure

• □ C Split dosing of the preparation is most useful for colonoscopies scheduled early in the morning

• □ D Right colon cleansing is normally suboptimal at 4 hours following the completion of the preparation

3. The patient presents for her colonoscopy. Which of the following types of polyp is particularly more common in the proximal colon?

• □ A Tubular

• □ B Tubulovillous

• □ C Villous

• □ D Serrated

4. Which of the following techniques is most important in detecting lesions in the proximal colon during colonoscopy?

• □ A Cecal intubation

• □ B Cap-fitted colonoscopy

• □ C Wide-angle colonoscopy

• □ D Autofluorescence