What are we missing when colon preparation is inadequate?

Abstract

Adequate colon preparation, defined by the ability to detect polyps 5 mm or larger,1Rex D.K. Petrini J.L. Baron T.H. et al.Quality indicators for colonoscopy.Gastrointest Endosc. 2006; 63: S16-S28Abstract Full Text Full Text PDF PubMed Scopus (433) Google Scholar is crucial for proper visualization during colonoscopy. Even in a well-prepared colon, however, colonoscopists miss neoplastic colon polyps.2Hixson L.J. Fennerty M.B. Sampliner R.E. et al.Prospective blinded trial of the colonoscopic miss-rate of large colorectal polyps.Gastrointest Endosc. 1991; 37: 125-127Abstract Full Text PDF PubMed Scopus (251) Google Scholar This issue is of particular importance in patients with more than 3 adenomas or advanced adenomas (defined as adenomas at least 1 cm, exhibiting villous histology, or with high-grade dysplasia), who are at increased risk for developing subsequent advanced colon neoplasia.3Winawer S.J. Zauber A.G. Fletcher R.H. et al.Guidelines for colonoscopy surveillance after polypectomy: a consensus update by the US Multi-Society Task Force on Colorectal Cancer and the American Cancer Society.Gastroenterology. 2006; 130: 1872-1885Abstract Full Text Full Text PDF PubMed Scopus (625) Google Scholar Two of the largest studies using tandem colonoscopy, in which patients undergo two colonoscopies on the same day, reported adenoma miss rates (defined as the number of adenomas found on repeat colonoscopy divided by the total number of adenomas found on both index and repeat colonoscopies) of 0% to 6% for adenomas at least 1 cm and greater miss rates as the size of the adenomas decreased.2Hixson L.J. Fennerty M.B. Sampliner R.E. et al.Prospective blinded trial of the colonoscopic miss-rate of large colorectal polyps.Gastrointest Endosc. 1991; 37: 125-127Abstract Full Text PDF PubMed Scopus (251) Google Scholar, 4Rex D.K. Cutler C.S. Lemmel G.T. et al.Colonoscopic miss rates of adenomas determined by back-to-back colonoscopies.Gastroenterology. 1997; 112: 24-28Abstract Full Text PDF PubMed Scopus (1374) Google Scholar Higher miss rates by colonoscopy for adenomas over 1 cm have been reported in CT colonography studies.5Pickhardt P.J. Nugent P.A. Mysliwiec P.A. et al.Location of adenomas missed by optical colonoscopy.Ann Intern Med. 2004; 141: 352-359Crossref PubMed Scopus (376) Google ScholarTo what degree are the benefits of colonoscopy, an excellent but imperfect tool, diminished when colon preparation is poor? Prior studies have suggested that suboptimal colon preparation significantly decreases the ability to detect colon polyps but not necessarily colon cancer.6Harewood G.C. Sharma V.K. de Garmo P. Impact of colonoscopy preparation quality on detection of suspected colonic neoplasia.Gastrointest Endosc. 2003; 58: 76-79Abstract Full Text Full Text PDF PubMed Scopus (582) Google Scholar, 7Froehlich F. Wietlisbach V. Gonvers J.J. et al.Impact of colonic cleansing on quality and diagnostic yield of colonoscopy: The European Panel of Appropriateness of Gastrointestinal Endoscopy European Multicenter Study.Gastrointest Endosc. 2005; 61: 378-384Abstract Full Text Full Text PDF PubMed Scopus (717) Google Scholar The extent to which unsatisfactory colon preparation impacts detection rates of adenomas in particular has been described only recently. Lebwohl et al8Lebwohl B. Kastrinos F. Glick M. et al.The impact of suboptimal bowel preparation on adenoma miss rates and the factors associated with early repeat colonoscopy.Gastrointest Endosc. 2011; 73: 1207-1214Abstract Full Text Full Text PDF PubMed Scopus (304) Google Scholar reported adenoma and advanced adenoma miss rates of 42% and 27%, respectively, in patients with suboptimal preparation at the time of index colonoscopy being performed for screening, diagnostic, and surveillance purposes. When the analysis was restricted to 72 asymptomatic patients undergoing screening colonoscopy, the adenoma and advanced adenoma miss rates increased to 43% and 37%, respectively.8Lebwohl B. Kastrinos F. Glick M. et al.The impact of suboptimal bowel preparation on adenoma miss rates and the factors associated with early repeat colonoscopy.Gastrointest Endosc. 2011; 73: 1207-1214Abstract Full Text Full Text PDF PubMed Scopus (304) Google ScholarIn this issue of Gastrointestinal Endoscopy, Chokshi et al9Chokshi R. Hovis C. Hollander T. et al.Prevalence of missed adenomas in patients with inadequate bowel preparation on screening colonoscopy.Gastrointest Endosc. 2012; 75: 1197-1203Abstract Full Text Full Text PDF PubMed Scopus (235) Google Scholar present data from a larger cohort of 373 asymptomatic, average-risk outpatients with inadequate colon preparation during screening colonoscopies performed over a 5-year period. Inadequate colon preparations in this study included “poor” preparations based on the Aronchick scale10Aronchick C.A. Lipshutz W.H. Wright S.H. et al.A novel tableted purgative for colonoscopic preparation: efficacy and safety comparisons with Colyte and Fleet Phospho-Soda.Gastrointest Endosc. 2000; 52: 346-352Abstract Full Text Full Text PDF PubMed Scopus (310) Google Scholar and those that were not thought to allow detection of polyps over 5 mm. Repeat colonoscopy was performed in 133 of these patients after 2-day colon preparation. All polyps were removed at the time of detection, and every colonoscopy was completed to the cecum. The adenoma detection rate, defined as the proportion of participants in whom at least one adenoma was identified, and adenoma miss rates were then calculated. Despite a seemingly adequate adenoma detection rate of 26% for the index screening colonoscopies based on recommended guidelines (at least 15% in women and 25% in men aged ≥50 years),1Rex D.K. Petrini J.L. Baron T.H. et al.Quality indicators for colonoscopy.Gastrointest Endosc. 2006; 63: S16-S28Abstract Full Text Full Text PDF PubMed Scopus (433) Google Scholar the authors report an adenoma miss rate of 48% and that advanced adenomas were found in 18% of patients undergoing repeat colonoscopy.9Chokshi R. Hovis C. Hollander T. et al.Prevalence of missed adenomas in patients with inadequate bowel preparation on screening colonoscopy.Gastrointest Endosc. 2012; 75: 1197-1203Abstract Full Text Full Text PDF PubMed Scopus (235) Google Scholar The adenoma miss rate could have been even higher because nearly one-fourth of patients who underwent repeat colonoscopy did not have adequate preparation, and patients whose initial colon preparation was so poor that the colonoscopy could not be safely completed to the cecum were not included in the analysis. These findings suggest that the current target adenoma detection rates are not appropriate measures of colonoscopy quality in the setting of inadequate colon preparation.Chokshi et al9Chokshi R. Hovis C. Hollander T. et al.Prevalence of missed adenomas in patients with inadequate bowel preparation on screening colonoscopy.Gastrointest Endosc. 2012; 75: 1197-1203Abstract Full Text Full Text PDF PubMed Scopus (235) Google Scholar also found that a majority of the missed advanced adenomas (80%) were located in the proximal colon when the preparation was inadequate, which parallels findings from other investigators that proximal location is a risk factor for missed colon cancer.11Singh H. Nugent Z. Demers A.A. et al.Rate and predictors of early/missed colorectal cancers after colonoscopy in Manitoba: a population-based study.Am J Gastroenterol. 2010; 105: 2588-2596Crossref PubMed Scopus (209) Google Scholar Potential explanations for this observation include missed sessile serrated adenomas, which often are located in the right side of the colon and may be difficult to detect even when colon preparation is ideal, and the greater difficulty in adequately cleaning the cecum and ascending colon.12Lasisi F. Rex D.K. Improving protection against proximal colon cancer by colonoscopy.Expert Rev Gastroenterol Hepatol. 2011; 5: 745-754Crossref PubMed Scopus (31) Google Scholar Although the specialty of the colonoscopist can significantly affect the mortality from proximal colon cancer after colonoscopy,13Singh H. Nugent Z. Demers A.A. et al.The reduction in colorectal cancer mortality after colonoscopy varies by site of the cancer.Gastroenterology. 2010; 139: 1128-1137Abstract Full Text Full Text PDF PubMed Scopus (360) Google Scholar this would not adequately explain the predominance of missed proximal colon advanced adenomas in the current study, seeing that all but one of the endoscopists were gastroenterologists.9Chokshi R. Hovis C. Hollander T. et al.Prevalence of missed adenomas in patients with inadequate bowel preparation on screening colonoscopy.Gastrointest Endosc. 2012; 75: 1197-1203Abstract Full Text Full Text PDF PubMed Scopus (235) Google ScholarAnother noteworthy finding in this study is that only 36% of patients with inadequate colon preparation returned for colonoscopy.9Chokshi R. Hovis C. Hollander T. et al.Prevalence of missed adenomas in patients with inadequate bowel preparation on screening colonoscopy.Gastrointest Endosc. 2012; 75: 1197-1203Abstract Full Text Full Text PDF PubMed Scopus (235) Google Scholar This highlights the need for improved patient education regarding the importance of repeating colonoscopy in a timely fashion after poor preparation and adhering to the preprocedure instructions to increase the likelihood of adequate colon preparation. Increased awareness by colonoscopists regarding the adenoma miss rate in this setting also is essential, which is illustrated by the observation that some patients were told to return up to 10 years after their index colonoscopies despite inadequate preparation.9Chokshi R. Hovis C. Hollander T. et al.Prevalence of missed adenomas in patients with inadequate bowel preparation on screening colonoscopy.Gastrointest Endosc. 2012; 75: 1197-1203Abstract Full Text Full Text PDF PubMed Scopus (235) Google ScholarHow should follow-up be managed for patients whose initial colon preparation is inadequate? Ideally, these patients should undergo repeat colonoscopy after additional colon preparation as soon as possible, for several reasons. First, prompt repeat colonoscopy would decrease the need to rely on the inherently subjective judgment of colonoscopists regarding the degree to which the colon preparation is inadequate. Although gastroenterologists tend to recommend earlier follow-up as colon preparation becomes increasingly suboptimal, they provide a wide range of recommendations regarding the precise timing of repeat colonoscopy in these situations, even when presented with standardized images.14Larsen M. Hills N. Terdiman J. The impact of the quality of colon preparation on follow-up colonoscopy recommendations.Am J Gastroenterol. 2011; 106: 2058-2062Crossref PubMed Scopus (30) Google Scholar Second, next-day colonoscopy after additional colon preparation can significantly reduce the likelihood of a second unsatisfactory colon preparation.15Ben-Horin S. Bar-Meir S. Avidan B. The outcome of a second preparation for colonoscopy after preparation failure in the first procedure.Gastrointest Endosc. 2009; 69: 626-630Abstract Full Text Full Text PDF PubMed Scopus (40) Google Scholar Finally, the potential for medical-legal liability exists if timely repeat evaluation of the colon is not undertaken when colon preparation is poor and an interval colon cancer is diagnosed in a short time period.16Bond J.H. Should the quality of preparation impact postcolonoscopy follow-up recommendations?.Am J Gastroenterol. 2007; 102: 2686-2687Crossref PubMed Scopus (16) Google Scholar Although the lack of reported missed colon cancers by Chokshi et al9Chokshi R. Hovis C. Hollander T. et al.Prevalence of missed adenomas in patients with inadequate bowel preparation on screening colonoscopy.Gastrointest Endosc. 2012; 75: 1197-1203Abstract Full Text Full Text PDF PubMed Scopus (235) Google Scholar is reassuring and consistent with findings from other groups,6Harewood G.C. Sharma V.K. de Garmo P. Impact of colonoscopy preparation quality on detection of suspected colonic neoplasia.Gastrointest Endosc. 2003; 58: 76-79Abstract Full Text Full Text PDF PubMed Scopus (582) Google Scholar, 7Froehlich F. Wietlisbach V. Gonvers J.J. et al.Impact of colonic cleansing on quality and diagnostic yield of colonoscopy: The European Panel of Appropriateness of Gastrointestinal Endoscopy European Multicenter Study.Gastrointest Endosc. 2005; 61: 378-384Abstract Full Text Full Text PDF PubMed Scopus (717) Google Scholar, 8Lebwohl B. Kastrinos F. Glick M. et al.The impact of suboptimal bowel preparation on adenoma miss rates and the factors associated with early repeat colonoscopy.Gastrointest Endosc. 2011; 73: 1207-1214Abstract Full Text Full Text PDF PubMed Scopus (304) Google Scholar repeat colonoscopy when colon preparation is suboptimal preferably should be performed as soon as possible, based on the high advanced adenoma miss rates reported in this setting.8Lebwohl B. Kastrinos F. Glick M. et al.The impact of suboptimal bowel preparation on adenoma miss rates and the factors associated with early repeat colonoscopy.Gastrointest Endosc. 2011; 73: 1207-1214Abstract Full Text Full Text PDF PubMed Scopus (304) Google Scholar The use of other modalities such as CT colonography, which, like colonoscopy, is imperfect in detecting all adenomas,5Pickhardt P.J. Nugent P.A. Mysliwiec P.A. et al.Location of adenomas missed by optical colonoscopy.Ann Intern Med. 2004; 141: 352-359Crossref PubMed Scopus (376) Google Scholar to evaluate the colon after initial poor colon preparation is a theoretical consideration. However, this may not be a cost-effective approach because 34% of patients in the current study had at least one adenoma identified on repeat colonoscopy that was not detected during the index examinations.9Chokshi R. Hovis C. Hollander T. et al.Prevalence of missed adenomas in patients with inadequate bowel preparation on screening colonoscopy.Gastrointest Endosc. 2012; 75: 1197-1203Abstract Full Text Full Text PDF PubMed Scopus (235) Google ScholarIt is clear that neoplastic colon polyps are being missed at a nontrivial rate when colon preparation is poor. The findings by Chokshi et al9Chokshi R. Hovis C. Hollander T. et al.Prevalence of missed adenomas in patients with inadequate bowel preparation on screening colonoscopy.Gastrointest Endosc. 2012; 75: 1197-1203Abstract Full Text Full Text PDF PubMed Scopus (235) Google Scholar reinforce prior recommendations that adequate colon preparation during the index colonoscopy is essential to providing appropriate recommendations regarding the timing of the next examination.3Winawer S.J. Zauber A.G. Fletcher R.H. et al.Guidelines for colonoscopy surveillance after polypectomy: a consensus update by the US Multi-Society Task Force on Colorectal Cancer and the American Cancer Society.Gastroenterology. 2006; 130: 1872-1885Abstract Full Text Full Text PDF PubMed Scopus (625) Google Scholar The adequacy of colon preparation should continue to be stressed in efforts to increase the quality of colonoscopy, now that we have a better understanding of what we are missing when colon preparation is inadequate.DisclosureThe author disclosed no financial relationships relevant to this publication. Adequate colon preparation, defined by the ability to detect polyps 5 mm or larger,1Rex D.K. Petrini J.L. Baron T.H. et al.Quality indicators for colonoscopy.Gastrointest Endosc. 2006; 63: S16-S28Abstract Full Text Full Text PDF PubMed Scopus (433) Google Scholar is crucial for proper visualization during colonoscopy. Even in a well-prepared colon, however, colonoscopists miss neoplastic colon polyps.2Hixson L.J. Fennerty M.B. Sampliner R.E. et al.Prospective blinded trial of the colonoscopic miss-rate of large colorectal polyps.Gastrointest Endosc. 1991; 37: 125-127Abstract Full Text PDF PubMed Scopus (251) Google Scholar This issue is of particular importance in patients with more than 3 adenomas or advanced adenomas (defined as adenomas at least 1 cm, exhibiting villous histology, or with high-grade dysplasia), who are at increased risk for developing subsequent advanced colon neoplasia.3Winawer S.J. Zauber A.G. Fletcher R.H. et al.Guidelines for colonoscopy surveillance after polypectomy: a consensus update by the US Multi-Society Task Force on Colorectal Cancer and the American Cancer Society.Gastroenterology. 2006; 130: 1872-1885Abstract Full Text Full Text PDF PubMed Scopus (625) Google Scholar Two of the largest studies using tandem colonoscopy, in which patients undergo two colonoscopies on the same day, reported adenoma miss rates (defined as the number of adenomas found on repeat colonoscopy divided by the total number of adenomas found on both index and repeat colonoscopies) of 0% to 6% for adenomas at least 1 cm and greater miss rates as the size of the adenomas decreased.2Hixson L.J. Fennerty M.B. Sampliner R.E. et al.Prospective blinded trial of the colonoscopic miss-rate of large colorectal polyps.Gastrointest Endosc. 1991; 37: 125-127Abstract Full Text PDF PubMed Scopus (251) Google Scholar, 4Rex D.K. Cutler C.S. Lemmel G.T. et al.Colonoscopic miss rates of adenomas determined by back-to-back colonoscopies.Gastroenterology. 1997; 112: 24-28Abstract Full Text PDF PubMed Scopus (1374) Google Scholar Higher miss rates by colonoscopy for adenomas over 1 cm have been reported in CT colonography studies.5Pickhardt P.J. Nugent P.A. Mysliwiec P.A. et al.Location of adenomas missed by optical colonoscopy.Ann Intern Med. 2004; 141: 352-359Crossref PubMed Scopus (376) Google Scholar To what degree are the benefits of colonoscopy, an excellent but imperfect tool, diminished when colon preparation is poor? Prior studies have suggested that suboptimal colon preparation significantly decreases the ability to detect colon polyps but not necessarily colon cancer.6Harewood G.C. Sharma V.K. de Garmo P. Impact of colonoscopy preparation quality on detection of suspected colonic neoplasia.Gastrointest Endosc. 2003; 58: 76-79Abstract Full Text Full Text PDF PubMed Scopus (582) Google Scholar, 7Froehlich F. Wietlisbach V. Gonvers J.J. et al.Impact of colonic cleansing on quality and diagnostic yield of colonoscopy: The European Panel of Appropriateness of Gastrointestinal Endoscopy European Multicenter Study.Gastrointest Endosc. 2005; 61: 378-384Abstract Full Text Full Text PDF PubMed Scopus (717) Google Scholar The extent to which unsatisfactory colon preparation impacts detection rates of adenomas in particular has been described only recently. Lebwohl et al8Lebwohl B. Kastrinos F. Glick M. et al.The impact of suboptimal bowel preparation on adenoma miss rates and the factors associated with early repeat colonoscopy.Gastrointest Endosc. 2011; 73: 1207-1214Abstract Full Text Full Text PDF PubMed Scopus (304) Google Scholar reported adenoma and advanced adenoma miss rates of 42% and 27%, respectively, in patients with suboptimal preparation at the time of index colonoscopy being performed for screening, diagnostic, and surveillance purposes. When the analysis was restricted to 72 asymptomatic patients undergoing screening colonoscopy, the adenoma and advanced adenoma miss rates increased to 43% and 37%, respectively.8Lebwohl B. Kastrinos F. Glick M. et al.The impact of suboptimal bowel preparation on adenoma miss rates and the factors associated with early repeat colonoscopy.Gastrointest Endosc. 2011; 73: 1207-1214Abstract Full Text Full Text PDF PubMed Scopus (304) Google Scholar In this issue of Gastrointestinal Endoscopy, Chokshi et al9Chokshi R. Hovis C. Hollander T. et al.Prevalence of missed adenomas in patients with inadequate bowel preparation on screening colonoscopy.Gastrointest Endosc. 2012; 75: 1197-1203Abstract Full Text Full Text PDF PubMed Scopus (235) Google Scholar present data from a larger cohort of 373 asymptomatic, average-risk outpatients with inadequate colon preparation during screening colonoscopies performed over a 5-year period. Inadequate colon preparations in this study included “poor” preparations based on the Aronchick scale10Aronchick C.A. Lipshutz W.H. Wright S.H. et al.A novel tableted purgative for colonoscopic preparation: efficacy and safety comparisons with Colyte and Fleet Phospho-Soda.Gastrointest Endosc. 2000; 52: 346-352Abstract Full Text Full Text PDF PubMed Scopus (310) Google Scholar and those that were not thought to allow detection of polyps over 5 mm. Repeat colonoscopy was performed in 133 of these patients after 2-day colon preparation. All polyps were removed at the time of detection, and every colonoscopy was completed to the cecum. The adenoma detection rate, defined as the proportion of participants in whom at least one adenoma was identified, and adenoma miss rates were then calculated. Despite a seemingly adequate adenoma detection rate of 26% for the index screening colonoscopies based on recommended guidelines (at least 15% in women and 25% in men aged ≥50 years),1Rex D.K. Petrini J.L. Baron T.H. et al.Quality indicators for colonoscopy.Gastrointest Endosc. 2006; 63: S16-S28Abstract Full Text Full Text PDF PubMed Scopus (433) Google Scholar the authors report an adenoma miss rate of 48% and that advanced adenomas were found in 18% of patients undergoing repeat colonoscopy.9Chokshi R. Hovis C. Hollander T. et al.Prevalence of missed adenomas in patients with inadequate bowel preparation on screening colonoscopy.Gastrointest Endosc. 2012; 75: 1197-1203Abstract Full Text Full Text PDF PubMed Scopus (235) Google Scholar The adenoma miss rate could have been even higher because nearly one-fourth of patients who underwent repeat colonoscopy did not have adequate preparation, and patients whose initial colon preparation was so poor that the colonoscopy could not be safely completed to the cecum were not included in the analysis. These findings suggest that the current target adenoma detection rates are not appropriate measures of colonoscopy quality in the setting of inadequate colon preparation. Chokshi et al9Chokshi R. Hovis C. Hollander T. et al.Prevalence of missed adenomas in patients with inadequate bowel preparation on screening colonoscopy.Gastrointest Endosc. 2012; 75: 1197-1203Abstract Full Text Full Text PDF PubMed Scopus (235) Google Scholar also found that a majority of the missed advanced adenomas (80%) were located in the proximal colon when the preparation was inadequate, which parallels findings from other investigators that proximal location is a risk factor for missed colon cancer.11Singh H. Nugent Z. Demers A.A. et al.Rate and predictors of early/missed colorectal cancers after colonoscopy in Manitoba: a population-based study.Am J Gastroenterol. 2010; 105: 2588-2596Crossref PubMed Scopus (209) Google Scholar Potential explanations for this observation include missed sessile serrated adenomas, which often are located in the right side of the colon and may be difficult to detect even when colon preparation is ideal, and the greater difficulty in adequately cleaning the cecum and ascending colon.12Lasisi F. Rex D.K. Improving protection against proximal colon cancer by colonoscopy.Expert Rev Gastroenterol Hepatol. 2011; 5: 745-754Crossref PubMed Scopus (31) Google Scholar Although the specialty of the colonoscopist can significantly affect the mortality from proximal colon cancer after colonoscopy,13Singh H. Nugent Z. Demers A.A. et al.The reduction in colorectal cancer mortality after colonoscopy varies by site of the cancer.Gastroenterology. 2010; 139: 1128-1137Abstract Full Text Full Text PDF PubMed Scopus (360) Google Scholar this would not adequately explain the predominance of missed proximal colon advanced adenomas in the current study, seeing that all but one of the endoscopists were gastroenterologists.9Chokshi R. Hovis C. Hollander T. et al.Prevalence of missed adenomas in patients with inadequate bowel preparation on screening colonoscopy.Gastrointest Endosc. 2012; 75: 1197-1203Abstract Full Text Full Text PDF PubMed Scopus (235) Google Scholar Another noteworthy finding in this study is that only 36% of patients with inadequate colon preparation returned for colonoscopy.9Chokshi R. Hovis C. Hollander T. et al.Prevalence of missed adenomas in patients with inadequate bowel preparation on screening colonoscopy.Gastrointest Endosc. 2012; 75: 1197-1203Abstract Full Text Full Text PDF PubMed Scopus (235) Google Scholar This highlights the need for improved patient education regarding the importance of repeating colonoscopy in a timely fashion after poor preparation and adhering to the preprocedure instructions to increase the likelihood of adequate colon preparation. Increased awareness by colonoscopists regarding the adenoma miss rate in this setting also is essential, which is illustrated by the observation that some patients were told to return up to 10 years after their index colonoscopies despite inadequate preparation.9Chokshi R. Hovis C. Hollander T. et al.Prevalence of missed adenomas in patients with inadequate bowel preparation on screening colonoscopy.Gastrointest Endosc. 2012; 75: 1197-1203Abstract Full Text Full Text PDF PubMed Scopus (235) Google Scholar How should follow-up be managed for patients whose initial colon preparation is inadequate? Ideally, these patients should undergo repeat colonoscopy after additional colon preparation as soon as possible, for several reasons. First, prompt repeat colonoscopy would decrease the need to rely on the inherently subjective judgment of colonoscopists regarding the degree to which the colon preparation is inadequate. Although gastroenterologists tend to recommend earlier follow-up as colon preparation becomes increasingly suboptimal, they provide a wide range of recommendations regarding the precise timing of repeat colonoscopy in these situations, even when presented with standardized images.14Larsen M. Hills N. Terdiman J. The impact of the quality of colon preparation on follow-up colonoscopy recommendations.Am J Gastroenterol. 2011; 106: 2058-2062Crossref PubMed Scopus (30) Google Scholar Second, next-day colonoscopy after additional colon preparation can significantly reduce the likelihood of a second unsatisfactory colon preparation.15Ben-Horin S. Bar-Meir S. Avidan B. The outcome of a second preparation for colonoscopy after preparation failure in the first procedure.Gastrointest Endosc. 2009; 69: 626-630Abstract Full Text Full Text PDF PubMed Scopus (40) Google Scholar Finally, the potential for medical-legal liability exists if timely repeat evaluation of the colon is not undertaken when colon preparation is poor and an interval colon cancer is diagnosed in a short time period.16Bond J.H. Should the quality of preparation impact postcolonoscopy follow-up recommendations?.Am J Gastroenterol. 2007; 102: 2686-2687Crossref PubMed Scopus (16) Google Scholar Although the lack of reported missed colon cancers by Chokshi et al9Chokshi R. Hovis C. Hollander T. et al.Prevalence of missed adenomas in patients with inadequate bowel preparation on screening colonoscopy.Gastrointest Endosc. 2012; 75: 1197-1203Abstract Full Text Full Text PDF PubMed Scopus (235) Google Scholar is reassuring and consistent with findings from other groups,6Harewood G.C. Sharma V.K. de Garmo P. Impact of colonoscopy preparation quality on detection of suspected colonic neoplasia.Gastrointest Endosc. 2003; 58: 76-79Abstract Full Text Full Text PDF PubMed Scopus (582) Google Scholar, 7Froehlich F. Wietlisbach V. Gonvers J.J. et al.Impact of colonic cleansing on quality and diagnostic yield of colonoscopy: The European Panel of Appropriateness of Gastrointestinal Endoscopy European Multicenter Study.Gastrointest Endosc. 2005; 61: 378-384Abstract Full Text Full Text PDF PubMed Scopus (717) Google Scholar, 8Lebwohl B. Kastrinos F. Glick M. et al.The impact of suboptimal bowel preparation on adenoma miss rates and the factors associated with early repeat colonoscopy.Gastrointest Endosc. 2011; 73: 1207-1214Abstract Full Text Full Text PDF PubMed Scopus (304) Google Scholar repeat colonoscopy when colon preparation is suboptimal preferably should be performed as soon as possible, based on the high advanced adenoma miss rates reported in this setting.8Lebwohl B. Kastrinos F. Glick M. et al.The impact of suboptimal bowel preparation on adenoma miss rates and the factors associated with early repeat colonoscopy.Gastrointest Endosc. 2011; 73: 1207-1214Abstract Full Text Full Text PDF PubMed Scopus (304) Google Scholar The use of other modalities such as CT colonography, which, like colonoscopy, is imperfect in detecting all adenomas,5Pickhardt P.J. Nugent P.A. Mysliwiec P.A. et al.Location of adenomas missed by optical colonoscopy.Ann Intern Med. 2004; 141: 352-359Crossref PubMed Scopus (376) Google Scholar to evaluate the colon after initial poor colon preparation is a theoretical consideration. However, this may not be a cost-effective approach because 34% of patients in the current study had at least one adenoma identified on repeat colonoscopy that was not detected during the index examinations.9Chokshi R. Hovis C. Hollander T. et al.Prevalence of missed adenomas in patients with inadequate bowel preparation on screening colonoscopy.Gastrointest Endosc. 2012; 75: 1197-1203Abstract Full Text Full Text PDF PubMed Scopus (235) Google Scholar It is clear that neoplastic colon polyps are being missed at a nontrivial rate when colon preparation is poor. The findings by Chokshi et al9Chokshi R. Hovis C. Hollander T. et al.Prevalence of missed adenomas in patients with inadequate bowel preparation on screening colonoscopy.Gastrointest Endosc. 2012; 75: 1197-1203Abstract Full Text Full Text PDF PubMed Scopus (235) Google Scholar reinforce prior recommendations that adequate colon preparation during the index colonoscopy is essential to providing appropriate recommendations regarding the timing of the next examination.3Winawer S.J. Zauber A.G. Fletcher R.H. et al.Guidelines for colonoscopy surveillance after polypectomy: a consensus update by the US Multi-Society Task Force on Colorectal Cancer and the American Cancer Society.Gastroenterology. 2006; 130: 1872-1885Abstract Full Text Full Text PDF PubMed Scopus (625) Google Scholar The adequacy of colon preparation should continue to be stressed in efforts to increase the quality of colonoscopy, now that we have a better understanding of what we are missing when colon preparation is inadequate. DisclosureThe author disclosed no financial relationships relevant to this publication. The author disclosed no financial relationships relevant to this publication. Prevalence of missed adenomas in patients with inadequate bowel preparation on screening colonoscopyGastrointestinal EndoscopyVol. 75Issue 6PreviewThe prevalence of missed polyps in patients with inadequate bowel preparation on screening colonoscopy is unknown. Full-Text PDF