I thank Drs. McDonnell and Loura for their interest in our paper. Their comments reflect what may be a misunderstanding about how our study was conducted, which procedures and patients were included, and the status and training of the endoscopists in our study.

First, all the endoscopists included in our study were staff physicians, and no trainees were involved. Second, more than half of the identified colonoscopies in the various databases used to build the study data set were not included in the analysis. Of the 35 945 colonoscopies identified, only 16 318 were eventually included in the study data set. For 1994 to 1996, the Colon Cancer Prevention Program database included only colonoscopies done within 6 months of a flexible sigmoidoscopy. Therefore, the numbers of colonoscopies per endoscopist described in our paper represent only a fraction of the endoscopic activity of these endoscopists. Each endoscopist performed more procedures than were included in the final study data set.

We had a substantially higher rate of polyp detection and removal in our sample than one would have expected in a purely screening or surveillance population, primarily because most of our patients had a previous positive result on a test, such as a flexible sigmoidoscopy, barium enema, or fecal occult blood test, or had a positive family history and had a higher rate of polyp detection and removal. Our perforation rate was clearly related to the removal tissue at colonoscopy, primarily through the use of snare resection with electrocautery. When no tissue was removed, only 3 perforations occurred in 5235 procedures, 2 of which were in patients with abnormal colons and were due to either unsuspected colitis or a tortuous, narrowed sigmoid colon.

Our study had systematic follow-up for all hospitalizations using automated, electronic data to track hospitalizations. I would presume the University of Washington experience reported by Drs. McDonnell and Loura, although not specified, relied on self-reported or opportunistic follow-up of postcolonoscopy complications. I would question whether they have complete information on delayed perforations that may have occurred in patients who were not hospitalized at their medical center. As described by Zubarik and colleagues (1), physician self-report of complications tends to underreport complications compared with systematic follow-up.

The 1 physician reported to have 6 complications over 808 cases performed many more colonoscopies than were reported in the study. He tended to be referred the more difficult polyp removal cases and therefore had a higher rate of complications than did some of his colleagues.