One of the problems we have encountered with colonoscopy in the last thirty years has been the incidence of missed colon cancer during colonoscopy. We have failed to see as dramatic a reduction in the incidence of colon cancer as we would have liked to see. There have been intensive efforts in the last ten to fifteen years to try and improve our yield at colonoscopy. Namely:-
Withdrawal time then is just one potential factor in increasing yield at colonoscopy and it is becoming more regularly reported. It is based on relatively recently published data that suggested an average withdrawal time of six minutes improved the yield of colonoscopy as compared with an average withdrawal time of less than that number. I personally report that number, but I regard it more important to spend time washing the colon, carefully analysing the mucosa with enhancing techniques such as dye spraying or Narrow Band Imaging, looking behind folds and re-examining areas that are known to be difficult to see well such as the right colon, behind flexures and in the sigmoid colon. Probably a better assessment of overall colonoscopy performance is the adenoma detection rate. This is also being measured by colonoscopists around the world and locally.