Usefulness of cap-assisted colonoscopy during colonoscopic EMR: a randomized, controlled trial

ORIGINAL ARTICLE: Clinical Endoscopy

Usefulness of cap-assisted colonoscopy during colonoscopic EMR: a randomized, controlled trial Seon-Young Park, MD, Hyun-Soo Kim, MD, PhD, Kyoung-Won Yoon, MD, Sung-Bum Cho, MD, PhD, Wan-Sik Lee, MD, PhD, Chang-Hwan Park, MD, PhD, Young-Eun Joo, MD, PhD, Sung-Kyu Choi, MD, PhD, Jong-Sun Rew, MD, PhD Gwangju, South Korea

Background: Clinical demand for total colonoscopy is increasing. Several articles have reported on the usefulness of a cap for faster cecal intubation and reduced patient discomfort, but results for polyp and adenoma detection have been inconsistent. Objective: To assess the efficacy of a cap attached to the tip of a colonoscope for detection and resection of polyps by experienced colonoscopists. Design: Prospective, randomized, controlled trial. Setting: A tertiary referral center. Patients and Intervention: A total of 329 patients who underwent colonoscopic EMR were randomized to cap-assisted colonoscopy (CAC) (CAC group, n ⫽ 166) or regular colonoscopy (RC) (RC group, n ⫽ 163). Main Outcome Measurements: Cecal intubation time, total procedure time, required time for colonoscopic EMR of each polyp, and missing polyp rate. Results: The cecal intubation time in the CAC group and RC group was 5.3 ⫾ 3.3 minutes and 5.8 ⫾ 3.7 minutes, respectively (P ⫽ .170). The total procedure time in the CAC group and RC group was 23.0 ⫾ 15.5 minutes and 29.2 ⫾ 13.4 minutes, respectively (P ⫽ .626). The time required for colonoscopic EMR of each polyp in the CAC group and RC group was 3.5 ⫾ 4.5 minutes and 4.2 ⫾ 5.1 minutes, respectively (P ⫽ .010). The number of polyps during the initial colonoscopy in the CAC group and RC group was 2.2 ⫾ 1.7 and 2.0 ⫾ 1.8, respectively (P ⫽ .221). The number of detected polyps during colonoscopic EMR in the CAC group and RC group was 3.4 ⫾ 2.7 and 2.7 ⫾ 1.9 (P ⫽ .003). The number of missed polyps in the CAC group and RC group was 1.1 ⫾ 1.5 and 0.8 ⫾ 0.9 (P ⫽ .024). Limitation: Single-center experience. Conclusions: CAC may reduce the time required for colonoscopic EMR of each polyp and may also improve the polyp detection rate. (Gastrointest Endosc 2011;74:869-75.)

Colorectal cancer is one of the major malignancies in Eastern countries including Korea, and its incidence is rapidly increasing. Colonoscopy is considered the criterion standard for the detection of colonic neoplasia, and colonoscopic polypectomy has been shown to be the most effective method for preventing colorectal cancer.1-3

As a result, the demand for colonoscopy has greatly increased worldwide, resulting in an increased workload for a relatively small number of experienced colonoscopists. Actually, as much as a 10-fold variation in adenoma detection was seen among endoscopists in a single practice.4 Polyps are missed even with meticulous technique, and

Abbreviations: CAC, cap-assisted colonoscopy; C-EMR, colonoscopic EMR; RC, regular colonoscopy.

doi:10.1016/j.gie.2011.06.005

DISCLOSURE: The authors disclosed no financial relationships relevant to this publication. See CME section; p. 912. Copyright © 2011 by the American Society for Gastrointestinal Endoscopy 0016-5107/$36.00

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Received February 23, 2011. Accepted June 1, 2011. Current affiliations: Department of Internal Medicine Chonnam National University Medical School, Gwangju, South Korea. Reprint requests: Hyun-Soo Kim, MD, PhD, Department of Internal Medicine, Chonnam National University Medical School, 8, Hak-dong, Dong-ku, Gwangju 501-757, South Korea.

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various additive or adjunctive technologies and techniques have been developed in an attempt to improve the yield of screening colonoscopy. Various techniques such as increasing withdrawal times and device-based approaches including a retrograde viewing device, highdefinition colonoscopies, chromoendoscopy, electronic image enhancement systems, and cap-assisted colonoscopy (CAC) have been developed and are commercially available.5-11 Among these techniques, a transparent cap (or “hood”) is a very simple device that can be attached to the tip of a colonoscope before performing the examination. The cap was initially designed for the mucosectomy procedure and was later used during colonoscopy to enhance colonic polyp detection.12 This CAC method was shown to be an effective rescue method for cases in which cecal intubation failed to be achieved.13 This benefit was more apparent in inexperienced colonoscopists.14 CAC studies in Asian populations found faster cecal intubation and reduced patient discomfort, but results for polyp and adenoma detection have been inconsistent.14-17 The aim of this prospective study was to assess the efficacy of CAC for the detection and resection of polyps by experienced colonoscopists.

PATIENTS AND METHODS This study was a prospective, randomized, controlled trial conducted between October 2007 and March 2009 at a single university hospital; the study was approved by the Institutional Review Board at Chonnam National University Hospital. All patients signed a written informed consent form.

Patients Patients 18 years of age or older who were able to give informed consent and were scheduled for elective colonoscopic EMR (C-EMR) at Chonnam National University Hospital were eligible for enrollment. All patients had undergone an initial regular colonoscopy (RC) either in our center or in other hospitals where small polyps were removed by standard forceps and unresectable polyps by only standard biopsy forceps were remained. Patients with previous colorectal surgery or with a colonic stricture or an obstructing tumor (with the diagnosis based on other investigations, such as CT or barium enema) or those with other acute surgical conditions, such as severe colitis, toxic megacolon, ischemic colitis, or acute GI bleeding were excluded from our study. Those patients who retained an unacceptable amount of residue in the colon, ie, solid or muddy stool that occupied or covered approximately 50% or more of the lumen or the colon wall, a situation that prohibited the safe and smooth insertion of a colonoscope, were also excluded. All patients performed standard bowel preparation before their colonoscopic procedure, which included a 3-day low-residue diet, followed by 4 L of polyethylene glycol. 870 GASTROINTESTINAL ENDOSCOPY Volume 74, No. 4 : 2011

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Take-home Message ●

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The use of a transparent cap during colonoscopic EMR contributed to shortening of the time required for polypectomy, especially of the nonpedunculated type. Cap-assisted colonoscopy is a useful method for reducing missed polyps in the patients in whom 3 or more colorectal polyps were detected in the previous examination.

Procedure Colonoscopies were performed by 2 experienced colonoscopists. These 2 colonoscopists previously performed more than 3000 procedures between them. Patients were randomized to either the CAC group or the RC group by using a computer-generated randomization sequence (blinded blocs of 10). Randomization used concealed allocation with a sealed, opaque envelope that designated either CAC or RC. Regular colonoscopes without a variable stiffness function (CF-240 or CF-Q240; Olympus Medical Systems, Tokyo, Japan) were used for examination to avoid adding another confounding factor to the study. CAC used a soft, transparent plastic cap (D-201-12704; Olympus), measuring 13.4 mm in its outer diameter and fitted to the distal tip of the colonoscope insertion tube so that 4 mm protruded. The C-EMR technique was used to excise all colorectal polyps where standard biopsy forceps (Olympus Optical Co, Ltd, Tokyo, Japan) or cold snare (SD-221U-25; Olympus Optical Co, Ltd, Tokyo, Japan) was deemed not suitable for removal. This usually included polypoid lesions more than 10 mm in size. Removal by using standard biopsy forceps or cold snare was done to excise colorectal polyps smaller than 10 mm. Polyps were first elevated by injecting normal saline solution with 0.2% indigo carmine dye into and around the lesion. Additional injections were performed, if necessary, during EMR. Typically, injection was performed at the side farthest from the endoscope, followed by the peripheries of the lesion (Injector Force, NM-200U-0423; Olympus Optical Co, Ltd). After submucosal injection, the open snare (SD-221U-25; Olympus Optical Co, Ltd) was placed around a portion of the lesion and was gently pressed against the mucosa. Excessive air was aspirated from the colon to decrease the distention and facilitate grasping of the targeted polyp. After snare excision, air was insufflated again to visualize the resection area. An attempt to fully resect or ablate the entire lesion in the first session was tried in every case. When en bloc resection was deemed technically impossible, the lesion was removed piecemeal, possibly including 1 to 3 mm of normal tissue in the lateral margin. Electrosurgery was performed using a combination of cutting (120 W) and coagulation current (60 W), using an ERBE-ICC 200 (ERBE Elektromedizin GmbH, Tübingen, Germany). www.giejournal.org

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Figure 1. Flowchart of the study.

The endoscopists recorded several steps during the procedure: colonoscope insertion into the rectum time, the time that it took to reach the cecum, removal time from the anus, and the time just before and just after C-EMR was performed. Based on these data, other measurements were calculated, such as the time required for cecal intubation, the total procedure time, and the time required for C-EMR of 1 polyp. We defined the time required for C-EMR for one polyp as how long it took to detect the polyp, inject submucosal fluid, resect the polyp, observe the resection area, and control immediate bleeding. We also calculated the withdrawal time by subtracting the cecal intubation time and the total required time for C-EMR from the total procedure time. If it was necessary to remove the colonoscope to retrieve resected polyps, we deducted the time between removal and reinsertion of the colonoscope in calculating of the total procedure time. The number of polyps detected during C-EMR was also recorded by the endoscopists. Complications, including bleeding, perforation, severe abdominal pain, and fever, were recorded prospectively.

Outcome measurement The primary endpoint of this study was to measure the time required for cecal intubation and to count the polyps missed in the 2 groups, ie, the CAC group and the RC group. The number of remaining polyps during the initial regular colonoscopic examination and the number of polyps detected during C-EMR, by either the CAC method or the RC method, were recorded. Missed polyps were defined as the polyps that were missed at the first regular colonoscopic examination but detected at the second C-EMR. The number of missed polyps was also counted. The secondary endpoints were calculation of the total www.giejournal.org

procedure time and the time required for C-EMR of 1 polyp and determining the complication rates.

Statistical methods We calculated the required sample size by using the following assumptions regarding miss rate: a 30% adenoma miss rate for the RC procedure,18,19 and a 10% adenoma miss rate with the CAC technique. We hypothesized that the CAC technique would be more effective to improve the detection of a missed polyp. To assign 80% power for detecting a threefold reduction in adenoma miss rates by using a ␹2 test with a 5% significance level in our study, we needed 62 polyps per group. We assumed that each patient would have 2 polyps and planned to enroll at least 124 participants. Continuous variables were presented as mean ⫾ standard deviation or median value (25%-75%). Non–normally distributed variables were log-transformed to achieve normality before analysis. The ␹2 test and Fisher exact test were used to compare categorical variables. A Student t test was used to compare continuous variables. P ⬍ .05 was considered statistically significant. All statistical evaluation was performed using SPSS version 18.0 (SPSS Inc, Chicago, Ill).

RESULTS Patients A total of 354 patients underwent C-EMR during the study period. Of these, 25 patients were excluded because of poor bowel preparation. The remaining 329 patients were all enrolled. There were 235 men and 94 women with a mean age of 60.3 ⫾ 10.3 years who were randomly assigned to the CAC group (n ⫽ 166) or the RC group (n ⫽ 163) (Fig. 1). The cecum was intubated in all patients. Volume 74, No. 4 : 2011 GASTROINTESTINAL ENDOSCOPY 871

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TABLE 1. Baseline demographic clinical characteristics of patients and outcomes in cap-assisted colonoscopy and regular colonoscopy (n ⴝ 329) Cap-assisted colonoscopy (n ⴝ 166)

Regular colonoscopy (n ⴝ 163)

P value

61.3 ⫾ 10.3

59.3 ⫾ 10.2

.096

Age, y, mean ⫾ SD Sex, no. (%)

.148

Male

125 (75.3)

110 (67.5)

Female

41 (24.7)

53 (32.5)

164.5 ⫾ 8.9

162.8 ⫾ 11.8

.150

Height, cm, mean ⫾ SD Body weight, kg, mean ⫾ SD

67.1 ⫾ 11.5

65.2 ⫾ 13.1

.181

Abdominal circumference, cm, mean ⫾ SD

85.8 ⫾ 8.8

84.4 ⫾ 8.9

.187

No. of patients with a history of abdominal surgery

16 (9.6)

10 (6.1)

.330

Diabetes, no. (%)

26 (15.7)

19 (11.7)

.370

Hypertension, no. (%)

49 (29.5)

45 (27.6)

.794

Cecal intubation time, min, mean ⫾ SD

5.3 ⫾ 3.3

5.8 ⫾ 3.7

.170

Total procedure time, min, mean ⫾ SD

23.0 ⫾ 15.5

29.2 ⫾ 13.4

.626

Withdrawal time, min, mean ⫾ SD

20.3 ⫾ 13.1

18.1 ⫾ 10.1

.074

3.5 ⫾ 4.5

4.2 ⫾ 5.1

.010

Required time for colonoscopic EMR/polyp SD, Standard deviation.

Baseline characteristics of patients are summarized in Table 1. We found no significant differences between the groups.

Cecal intubation time and procedure time There was no difference in the cecal intubation time, the procedure time, and the withdrawal time between the 2 groups (P ⬎ .05). However, the mean time (⫾ standard deviation) required for EMR of 1 polyp in the CAC group and in polyp in the RC group was 3.5 ⫾ 4.5 minutes and 4.2 ⫾ 5.1 minutes, respectively (P ⫽ .010, Table 1). There was no difference in the time required for EMR of a pedunculated polyp. However, there was a significant difference between the 2 groups in the time required for EMR of a nonpedunculated polyp (CAC group vs RC group, 3.4 ⫾ 5.0 minutes vs 3.9 ⫾ 4.7 minutes, P ⫽ .018).

Detection of colorectal polyps There was no significant difference in the number of detected polyps between the 2 groups during the first examination (P ⫽ .221). However, there was a significant difference in the number of detected polyps between the 2 groups during C-EMR; namely, there were 3.4 ⫾ 2.7 polyps being detected per patient in the CAC group versus 2.7 ⫾ 1.9 polyps being detected per patient in the RC group (P ⫽ .003). There was no significant difference in the size of polyps during C-EMR between the 2 groups. In addition, the number of missed polyps in the CAC group 872 GASTROINTESTINAL ENDOSCOPY Volume 74, No. 4 : 2011

(1.1 ⫾ 1.5) was higher than that in the RC group (0.8 ⫾ 0.9, P ⫽ .024), as shown in Table 2. In a subgroup analysis of patients with 3 or more polyps detected during the first examination, the number of missed polyps in the CAC group (1.65 ⫾ 2.13) was also higher than that in the RC group (0.86 ⫾ 0.99, P ⫽ .026, Table 3).

Polyp characteristics A total of 667 polyps were detected during the first examination in 329 patients. In contrast, a total of 1002 polyps were detected during C-EMR, representing an overall miss rate of 33.4%. When classified, 82.5% were adenomatous polyps, 3.8% malignant polyps, and 13.7% nonadenomatous polyps. There was no significant difference in the size and distribution of the missed polyps between the 2 groups (Table 4).

Complication There was no significant difference in the complication rate between the 2 groups. There was no cap displacement during the study. There were no deaths, perforation, or severe GI bleeding reported.

DISCUSSION Because of the rapid progress of colonoscopic technology, colonoscopy is becoming increasingly popular for the management of colorectal disease. As a result, www.giejournal.org

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TABLE 2. Number polyps found on the first examination, the polyps detected during colonoscopic EMR, and the missed polyps Cap-assisted colonoscopy (n ⴝ 166)

Regular colonoscopy (n ⴝ 163)

P value

No. of polyps found on first examination, mean ⫾ SD

2.2 ⫾ 1.7

2.0 ⫾ 1.8

.221

No. of polyps found during colonoscopic EMR, mean ⫾ SD

3.4 ⫾ 2.7

2.7 ⫾ 1.9

.003

Size of polyps found during colonoscopic EMR, mm, mean ⫾ SD

11.65 ⫾ 3.86

12.16 ⫾ 5.36

.770

1.1 ⫾ 1.5

0.8 ⫾ 0.9

.024

No. of missed polyps, mean ⫾ SD SD, Standard deviation.

TABLE 3. Subgroup analysis of patients with 3 or more polyps found during the first examination Cap-assisted colonoscopy (n ⴝ 53)

Regular colonoscopy (n ⴝ 38)

P value

No. of polyps found on first examination, mean ⫾ SD

4.26 ⫾ 1.95

4.27 ⫾ 2.61

.976

No. of polyps found during colonoscopic EMR, mean ⫾ SD

5.85 ⫾ 3.17

4.86 ⫾ 2.64

.026

No. of missed polyps, mean ⫾ SD

1.65 ⫾ 2.13

0.86 ⫾ 0.99

.026

SD, Standard deviation.

TABLE 4. Characteristics of missed polyps (N ⴝ 335) Cap-assisted colonoscopy

Regular colonoscopy

178

157

5 (5-7.5)

6 (5-7)

.774

1-4

35/178 (19.7%)

19/157 (12.1%)

.084

ⱖ5

143/178 (80.3%)

138/157 (87.9%)

Total no. of missed polyps Size of missed polyps, mm, median (25%-75%)

Location

P value

.395

Cecum/AC/DC/rectum

83/178 (46.6%)

65/157 (41.4%)

HF/T/SF/SD-RS

95/178 (53.4%)

92/157 (58.6%)

AC, Ascending colon; DC, descending colon; HT, hepatic flexure; T, transverse colon; SF, splenic flexure; SD-RS, sigmoid colon.

the demand for colonoscopy has greatly increased, resulting in an increased workload for a relatively small number of experienced endoscopists worldwide. The transparent cap or hood is commonly available, reusable, and inexpensive.13 The use of a transparent cap for colonoscopy was first reported was by Inoue et al20 in 1993. The expected advantages of a cap attachment to the tip of a colonoscope are as follows: (1) maintains a clear visual field by keeping an appropriate distance between the colonoscope and the colonic mucosa; (2) enables easier anticipation of the direction in which the colonoscope should be advanced, with less air insufflation, which allows for a more comfortable examination; www.giejournal.org

and (3) offers a better quality examination by making it easier to observe the mucosa behind the folds and flexures. Recently, its usefulness for easier focusing during magnifying colonoscopy was reported.10,21,22 CAC performed by trainee endoscopists resulted in high rates of cecal intubation and shortening of the cecal intubation time in difficult cases. However, when this technique was replicated by experienced endoscopists and compared with colonoscopy without a cap, there failed to be a difference in the cecal intubation time.12,14 In our randomized, controlled study, C-EMR was performed by experienced endoscopists and the use of a transparent cap did not contribute to the shortening of the cecal Volume 74, No. 4 : 2011 GASTROINTESTINAL ENDOSCOPY 873

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Figure 2. A, Regular colonoscopy could not reveal the sessile polyp. B-D, Cap-assisted colonoscopy revealed the undetected sessile polyp by depressing the folds and flexures during colonoscopic EMR.

intubation time and the total procedure time. However, the use of a transparent cap contributed to the shortening of the time required for EMR of 1 polyp, especially the nonpedunculated type. A possible explanation is that the use of a transparent cap may help to stabilize the colonoscope by hooking the tip of the endoscope at acute bends or by depressing the folds and flexures during polypectomy (Fig. 2). This advantage may make polypectomy easier and may shorten the time required for polypectomy. In contrast, for the pedunculated type, the entrance of a pedunculated polyp into the cap may even interfere with the visual field. Theoretically, it is expected that the folds can be extended by the cap, which results in easier observation behind them and may improve the polyp or adenoma detection rate; however, CAC cannot be safely retroflexed, and debris and feces tend to collect within the cap, which may interfere with an accurate visual field and thus with polyp or adenoma detection. Results of previous studies of polyp and adenoma detection have been inconsistent.12,14-17,23 In our study, we showed that the average number of missed colorectal polyps was significantly higher in the CAC group than in the RC group. In particular, in patients with 3 or more polyps detected during the first examination, there was a significant difference in the number of missed polyps between the 2 groups. In other words, the 874 GASTROINTESTINAL ENDOSCOPY Volume 74, No. 4 : 2011

CAC method is a useful method for reducing missed polyps in patients with 3 or more colorectal polyps detected in the previous examination. Limitations of this study include the fact that it was a single-center study involving only 2 operators and that, like most endoscopic trials, the study was unblinded to the endoscopists. We did not account for multiple comparisons due to a small sample size in the subgroup analysis. In summary, the CAC performed by experienced colonoscopists did not shorten the cecal intubation time and the total procedure time. However, CAC shortened the time required for EMR of a polyp. Furthermore, the CAC improved the detection of missed polyps, especially in the patients with known multiple colorectal polyps. In conclusion, the CAC is a safe, simple, and inexpensive technology that could reduce the time required for EMR of a polyp and may improve polyp detection, especially when multiple colorectal polyps have been seen on previous colonoscopy. REFERENCES 1. Rex DK, Rahmani EY, Haseman JH, et al. Relative sensitivity of colonoscopy and barium enema for detection of colorectal cancer in clinical practice. Gastroenterology 1997;112:17-23.

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2. Winawer SJ, Zauber AG, O’Brien MJ, et al. Randomized comparison of surveillance intervals after colonoscopic removal of newly diagnosed adenomatous polyps. The National Polyp Study Workgroup. N Engl J Med 1993;328:901-6. 3. Winawer SJ, Zauber AG, Ho MN, et al. Prevention of colorectal cancer by colonoscopic polypectomy. The National Polyp Study Workgroup. N Engl J Med 1993;329:1977-81. 4. Barclay RL, Vicari JJ, Doughty AS, et al. Colonoscopic withdrawal times and adenoma detection during screening colonoscopy. N Engl J Med 2006;355:2533-41. 5. Overholt BF, Brooks-Belli L, Grace M, et al. Withdrawal times and associated factors in colonoscopy: a quality assurance multicenter assessment. J Clin Gastroenterol 2010;44:e80-6. 6. DeMarco DC, Odstrcil E, Lara LF, et al. Impact of experience with a retrograde-viewing device on adenoma detection rates and withdrawal times during colonoscopy: the Third Eye Retroscope study group. Gastrointest Endosc 2010;71:542-50. 7. Waye JD, Heigh RI, Fleischer DE, et al. A retrograde-viewing device improves detection of adenomas in the colon: a prospective efficacy evaluation (with videos). Gastrointest Endosc 2010;71:551-6. 8. Rex DK, Helbig CC. High yields of small and flat adenomas with highdefinition colonoscopes using either white light or narrow band imaging. Gastroenterology 2007;133:42-7. 9. Stoffel EM, Turgeon DK, Stockwell DH, et al. Chromoendoscopy detects more adenomas than colonoscopy using intensive inspection without dye spraying. Cancer Prev Res (Phila) 2008;1:507-13. 10. Dafnis GM. Technical considerations and patient comfort in total colonoscopy with and without a transparent cap: initial experiences from a pilot study. Endoscopy 2000;32:381-4. 11. Rastogi A, Keighley J, Singh V, et al. High accuracy of narrow band imaging without magnification for the real-time characterization of polyp histology and its comparison with high-definition white light colonoscopy: a prospective study. Am J Gastroenterol 2009;104:2422-30.

12. Matsushita M, Hajiro K, Okazaki K, et al. Efficacy of total colonoscopy with a transparent cap in comparison with colonoscopy without the cap. Endoscopy 1998;30:444-7. 13. Lee YT, Hui AJ, Wong VW, et al. Improved colonoscopy success rate with a distally attached mucosectomy cap. Endoscopy 2006;38:739-42. 14. Kondo S, Yamaji Y, Watabe H, et al. A randomized controlled trial evaluating the usefulness of a transparent hood attached to the tip of the colonoscope. Am J Gastroenterol 2007;102:75-81. 15. Harada Y, Hirasawa D, Fujita N, et al. Impact of a transparent hood on the performance of total colonoscopy: a randomized controlled trial. Gastrointest Endosc 2009;69:637-44. 16. Horiuchi A, Nakayama Y. Improved colorectal adenoma detection with a transparent retractable extension device. Am J Gastroenterol 2008;103: 341-5. 17. Lee YT, Lai LH, Hui AJ, et al. Efficacy of cap-assisted colonoscopy in comparison with regular colonoscopy: a randomized controlled trial. Am J Gastroenterol 2009;104:41-6. 18. Rex DK, Cutler CS, Lemmel GT, et al. Colonoscopic miss rates of adenomas determined by back-to-back colonoscopies. Gastroenterology 1997;112:24-8. 19. van Rijn JC, Reitsma JB, Stoker J, et al. Polyp miss rate determined by tandem colonoscopy: a systematic review. Am J Gastroenterol 2006; 101:343-50. 20. Inoue H, Takeshita K, Hori H, et al. Endoscopic mucosal resection with a cap-fitted panendoscope for esophagus, stomach, and colon mucosal lesions. Gastrointest Endosc 1993;39:58-62. 21. Yap CK, Ng HS. Cap-fitted gastroscopy improves visualization and targeting of lesions. Gastrointest Endosc 2001;53:93-5. 22. Urita Y, Nishino M, Ariki H, et al. A transparent hood simplifies magnifying observation of the colonic mucosa by colonoscopy. Gastrointest Endosc 1997;46:170-2. 23. Tada M, Inoue H, Yabata E, et al. Feasibility of the transparent cap-fitted colonoscope for screening and mucosal resection. Dis Colon Rectum 1997;40:618-21.

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