Endoscopic estimation of size: improved accuracy by directed teaching.

Previous studies have demonstrated the inaccuracy of endoscopic estimation of size. Although several devices have been developed to help improve estimation of size, none are convenient for clinical use. We have designed and evaluated a clinical teaching protocol to aid endoscopists in better estimating size. Thirteen "endoscopists" with varying levels of experience (none, less than 1 year, more than 1 year) estimated the size of six steel ball bearings placed into a model colon and viewed with a videoendoscope. They were then taught to compensate for optic distortion and retested immediately after teaching and again 1 month later. The mean error of estimation decreased from 28% before teaching to 8% after teaching (p < .05) and rose to 12% 1 month later (p < .05). Although the indices of mean error decreased immediately after teaching in all groups, only those individuals with less than 1 year of endoscopic experience retained the improvement 1 month after teaching. We conclude that endoscopists can be taught how to compensate for the optic distortion encountered during endoscopy. This teaching is most effective if performed early in the training program.