Background: Colonoscopy is the gold standard for the detection of colon polyps and cancers, but failed detections can occur and the reasons are incompletely understood.
Methods: During a retrospective evaluation of the sensitivity of barium enema and colonoscopy in 20 Indiana Hospitals, we encountered 47 cases of colorectal cancer in which a colonoscopy performed within 3 years of the diagnosis had not detected the cancer. Cases were reviewed for location of tumor, extenuating factors, pathologic features, delay in diagnosis from failed detection, and who performed the examination.
Results: Failed detection was more likely when colonoscopy was performed by a nongastroenterologist than a gastroenterologist (odds ratio 5:36, 95% CI [2.94,9.77]). Twenty-seven cancers were "missed," and 20 were estimated to be not reached. However, the location of missed tumors and a general absence of adequate documentation of cecal intubation suggested that some cecal and ascending colon cancers recorded as missed may actually have been not reached. Variation in sensitivity among gastroenterologists suggested that meticulous examination is also important in maximizing sensitivity.
Conclusions: These cases suggest several factors that might improve the quality and sensitivity of colonoscopy: (1) examiners should receive adequate training, (2) cecal intubation rates should be high, (3) cecal intubation should be verified by specific landmarks in all cases, (4) failure to reach the cecum should be followed by prompt barium enema, and (5) meticulous examination would appear to improve sensitivity for cancer detection.