Accuracy of Colonoscopy- missed lesion, missed opportunities

Post colonoscopy Colorectal Cancers are Preventable
A Population-Based Study
Chantal M C le Clercq, Mariëlle W E Bouwens, Eveline J A Rondagh, C Minke Bakker, Eric T P Keulen, Rogier J de Ridder, Bjorn Winkens, Ad A M Masclee, Silvia Sandulean
Gut. 2014; 63(6): 957-963.
In this study the investigators found that the majority of PCCRCs (86%) could have been avoided, being caused by missed or incompletely removed lesions and inadequate examination or surveillance. The missed cancers were more likely to be found in the right colon (caecum/ascending colon), to be smaller in size (so called flat-lesions). This type of lesion has a flat macroscopic appearance that spread laterally across the bowel surface rather than into the lumen. They are less common than prevalent CRCs, suggesting that they have originated from overlooked precursors at the index colonoscopy. These results illustrate the importance of developing practical skills for accurate detection and resection of all precursor lesions, with special attention to small, flat and proximally located lesions.
The study found that procedural factors accounted for the majority of PCCRCs. Two observations explain these findings; —namely, missed and incompletely removed lesions. With regard to the former, a number of other studies now suggest that flat or depressed colorectal adenomas lead to the development of PCCRCs, often being overlooked at a previous examination, being a more challenging resection[34] or perhaps a more aggressive biological behavior. Information on clinicopathological features, particularly the macroscopic appearance of PCCRCs, is scarce. This study is one of the few to examine the clinical features and potential explanations of PCCRCs and is the first non-Japanese study to report that a substantial proportion of PCCRCs (31% of the early (T1) PCCRCs and 45% of all diagnosed PCCRCs) had a flat macroscopic appearance.
An additional finding of the study is that incomplete polypectomy accounted for 8.8% of all PCCRCs. We specifically focused on the resection of advanced adenomas as up to 35% of these lesions may progress to cancer within 10 years.[43,44] In a study of 417 polyps resected by experienced gastroenterologists, Pohl et al [34] found a comparable rate of incompletely resected adenomas (10.1%, 95% CI 6.9% to 13.3%). Data on the potential impact of incomplete polypectomy on the occurrence of PCCRCs vary widely, ranging from 2.4%[27] to 26%.[45]
In the present study we did not find a significant association between the occurrence of PCCRCs and the specialty of endoscopists or individual clustering of PCCRC cases. This is in line with some studies,[15] but contradicts several others, which have shown that patients with PCCRCs are more likely to have undergone a colonoscopy by a non-gastroenterologist. It is possible that the relative homogeneity with regard to equipment, facilities used and supportive personnel might explain such findings. Notably, in our study, missed lesions accounted for most of the PCCRCs in university and non-university settings, indicating opportunities for future improvements. In contrast, incomplete resection appeared to be more likely to be a cause of PCCRCs in a non-university than in a university setting.
The incidence rate of PCCRCs in our study was 2.9% of all diagnosed CRCs, corresponding to 1.8 per 1000 colonoscopies. This rate is relatively low and consistent with previous data thus conferring generalisability for our routine practice. It is, however, difficult to compare the outcomes of different studies with regard to incidences of PCCRCs due to large variations in methodology (definition of PCCRCs, retrospective vs. prospective design, differences in populations examined).
In line with previous studies, this paper found that patients with PCCRCs tended to be older with co-morbid diseases including such as heart disease or or pre-existing other gastrointestinal diseae- specifically diverticular disease. Diverticular disease is associated with incomplete colonoscopy. It is likely that poor bowel preparation, which is more common in older and fragile patients with comorbidity, increases the risk of missing lesions. Interstingly, patients with PCCRC in this study were more likely to have a family history of CRC than those with prevalent CRCs (5.4% vs. 1.6%). Although this observation is based on a small number of cases, it illustrates the importance of taking a family history taking and applying strict BSG surveillance guidelines in higher risk groups. In summary, this study demonstrated that PCCRCs accounted for 2.9% of all diagnosed CRCs, most of which could be explained by missed or incompletely resected lesions, with a predominant proximal location and a flat macroscopic appearance. Systematic training of endoscopists, with a focus on lesion recognition and efficient removal of flat precursors, has the potential to prevent PCCRCs.
Viewpoint; This is another Important study that raises the issue of quality outcomes and colonoscopy. Colonoscopy, will vary in it's accuracy. It is dependent on many factors including the bowel preparation and the colonoscopist performing the test. Key performance data should be available on individual colonoscopists and endoscopic units including completion rates, complication rates and diagnostic accuracy (polyp detection rates) and complete resection rates. This is available in most endoscopic units but is not made public as yet. CMH

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