Diagnostic failure in colonoscopies for malignant disease

While colonoscopy has become established as more accurate than double contrast barium enema for detecting colonic polyps and cancers, as well as offering the opportunity for therapy, there are occasional instances where colonoscopy is misleading. The present study is to determine what problems occur, with a view to finding a solution.

The records of the Colorectal Project at the Princess Alexandra Hospital indicate retrospectively that 346 patients have been correctly diagnosed with cancer of the colon and rectum by colonoscopy in the 5 years up to October 1996. During the same time eight patients (2.3%) were recorded at the same hospital as being misdiagnosed by colonoscopy, the lesion being either missed completely or misplaced.

In five of these patients there was failure to recognize that the whole colon had not been examined endoscopically, thereby missing a more proximal lesion. In two patients the lesion was missed although the entire colon was examined. In one patient the lesion was discovered but inaccurately sited. Six of these mistakes would have been obviated by the routine use of fluoroscopy to confirm the totality of the colonoscopy and to site any lesions found. The other two cases occurred because of failure to remember that colonic examination during withdrawal should be performed meticulously back as far as the anal canal. Failure to diagnose a colon cancer on the initial colonoscopy led to an average delay of 6 months for definitive care.

It is recommended that fluoroscopy be used routinely during colonoscopy to site accurately any lesions found, and to confirm the completeness of insertion if reliable landmarks, including terminal ileum, are not clearly identified.