Missed colonic adenomas in routine primary care endoscopy: a prospective tandem colonoscopy study

Colonoscopy is the gold standard in the diagnosis of colorectal neoplasia. Several lines of independent evidence, however, suggest that a significant number of small adenomas and also some advanced lesions are missed even by experienced endoscopists. With large-scale screening colonoscopy programmes installed, information on quality of colonoscopy in primary care is essential, but not available. Between July 2006 and December 2008, a total of 40 patients (23 men and 17 women, median age: 69 years) underwent a second colonoscopy within 42 days after the first endoscopy (median: 11 days), in all cases exclusively for clinical reasons. Index colonoscopy was performed by 14 endoscopists in 6 hospitals and 4 private practices. Data on all consecutive patients were collected prospectively. A total of 98 neoplastic lesions were identified in 34 patients at the index colonoscopy, an additional 53 adenomas were removed at the second colonoscopy, 33 of them smaller than 5 mm. 25 out of 53 missed adenomas were identified between the coecum and the right colonic flexure. 12 of the additional lesions were considered significant lesions (larger than 10 mm or tubulovillous adenoma), nine of these were located between the coecum and the right colonic flexure. In 24 patients repeat colonoscopy detected adenomas not described in the original report. In eight patients a total of 12 significant lesions were removed, nine of these were located between the coecum and the right colonic flexure. About one-third of adenomas were missed in 40 routine colonoscopies, most of them only small and therefore probably of little clinical significance. However, 12 significant lesions were missed in 8 patients. Adenomas in the right colon seem to be a particular problem.