Now or later? Strategy for removing small colorectal polyps

Effective colonoscopic polypectomy requires a balance between the efficacy and safety of polyp removal. Despite widespread use, the technique of colonoscopic polypectomy has not been adequately studied, optimized, and standardized. The more basic the issue, the harder it is to find an answer as to what the best approach is and the larger the observed variability among endoscopists. A survey of American College of Gastroenterology members revealed considerable inconsistency in the types of accessories, current settings, and submucosal injection policy used for polypectomy [1]. One of the unanswered questions is whether polyps should be removed during both endoscope insertion and withdrawal, or during withdrawal only. The concept of performing polypectomy on withdrawal is driven only by a theoretical fear of causing hemorrhage or perforation at the polypectomy site because of tearing forces associated with endoscope insertion. On the other hand, doing polypectomy both on insertion and withdrawal could theoretically avoid difficulties in finding polyps again on withdrawal and reduce polyp miss rates. This could further translate into reduced variation in polyp and adenoma detection rates and have immediate consequences for patients [2]. Although most endoscopists agree that large polyps need to be removed on withdrawal only, the approach to smaller polyps remains unclear.

In this issue of Endoscopy, Wildi and colleagues present the results of a first single-center randomized controlled trial comparing the policies of removing polyps 10 mm or smaller during both insertion and withdrawal of the endoscope or on withdrawal only [3]. The authors highlight three major findings of the study. First, 3.3 % of polyps detected on insertion and/or withdrawal were missed if polyps were removed during withdrawal only, whereas by definition no polyps were missed if removal was done during both insertion and withdrawal. Second, the total colonoscopy time was not significantly different between the study groups (P = 0.176). Third, patient discomfort, which was self-assessed on the day after colonoscopy, was not significantly different between the study groups and there were no complications in either group. These findings led the authors to recommend the removal of polyps up to 10 mm on both insertion and withdrawal. However, there are certain methodological drawbacks that give rise to hesitation in fully accepting the conclusions of the study.

Were the polyps really missed? The definition of “missed polyps” used in the study is misleading. Usually when we refer to missed polyps we understand that these were polyps that were not seen at all during the index colonoscopy. The “missed” status can only be given if repeated examination is performed, usually in the so-called segmental fashion. Here, in this study, polyps were not missed; on the contrary, they were seen but were not found again. The question is why they were not found the second time. It seems the search was not long enough or the withdrawal technique was not optimal.

Moreover, the study was not specifically designed to measure the polyp miss rate but primarily to detect differences in time between the two strategies, so the miss rate has limited value as a main finding in this study. With the authors’ definition of miss rate, the possibility of missing polyps in group A (polyps removed during both insertion and removal) is excluded, which, of course, is not valid; some polyps must have been missed in that group as well. Additionally, the assessment of polyp location, size, and even shape could have been different on insertion and withdrawal, so it is difficult to be sure that polyps seen on insertion were not removed on withdrawal. A magnetic endoscope locating device was not used, 11 of 13 polyps classified as missed were located in the descending-sigmoid colon, and equal numbers of polyps were detected in both groups making our hypothesis plausible. Moreover, contrary to the primary hypothesis of this study that total colonoscopy time would be 8 minutes longer in the group with polyp removal on withdrawal only (because of difficulty in finding the polyps again), it was actually 2 minutes shorter. In conjunction with the fact that the endoscopists were aware of the study hypothesis, it suggests that the time spent re-detecting the missed polyps was insufficient. Additionally, if the study had been designed to assess the real polyp miss rates, it would have been constructed as a tandem colonoscopy study [4]: in one arm, polyps would have been removed during insertion and withdrawal whereas they would have been removed on withdrawal only in the second group, and then a second-look colonoscopy would have been performed in both groups.

Were both procedures equally tolerable to patients? Although patient discomfort was not statistically different between the groups (P = 0.075), the study may not have been powered enough to show the difference in this secondary endpoint. Furthermore, all the patients were sedated with propofol or midazolam and/or meperidine, and discomfort was assessed only on the day after the colonoscopy using a 4-point verbal rating scale, all of which could have attenuated the differences in tolerance. If the study was designed to assess patient discomfort, it should also have included an intraprocedural pain assessment conducted by the nurses, using a visual analog scale, and recording the dose of sedatives used [5] [6].

One of the most relevant questions here is whether there is a difference in complication rates between the two policies. The 30-day data for complications from colonoscopy were not systematically collected, and the study was not powered to answer this question. One may consider a 30-day complication endpoint unrealistic, but the size of the trial is not that large. Assuming a 0.65 % serious complication rate following removal of polyps up to 10 mm [7] on withdrawal only, and a three times higher risk if polyps are removed during both insertion and withdrawal, 1125 patients are needed in each arm to achieve 80 % power with a 0.05 level of significance.

We think that the study by Wildi and colleagues has opened the door for scientific discussion on the issue of whether polyps up to 10 mm should be removed during both withdrawal and insertion of the endoscope, or during withdrawal only. Achieving even minor improvement in such a basic strategy could have a major widespread impact on clinical practice. Wildi et al. suggest that immediate removal is better; we believe that mastering the withdrawal technique, so that endoscopists can perform a perfect or nearly perfect examination of the whole surface of the large bowel, would be much more important than trying to quickly remove a small polyp that is just visible. Such a policy would allow endoscopists to concentrate first on a quick, painless insertion phase of the colonoscopy and only after that to concentrate on a perfect withdrawal technique. One should not forget that polypectomy during insertion indeed causes distraction and excessive insufflation of the bowel, and prolongs the painful phase of the colonoscopy possibly leading to an increased dosage of sedatives.

We call for additional studies to answer the research questions that the investigation by Wildi et al. brings to light.

• References

• 1 Singh N, Harrison M, Rex DK. A survey of colonoscopic polypectomy practices among clinical gastroenterologists. Gastrointest Endosc 2004; 60: 414-418
• 2 Kaminski MF, Regula J, Kraszewska E et al. Quality indicators for colonoscopy and the risk of interval cancer. N Engl J Med 2010; 362: 1795-1803
• 3 Wildi SM, Schoepfer AM, Vavricka SR et al. Colorectal polypectomy during insertion and withdrawal or only during withdrawal? A randomized controlled trial. Endoscopy 2012; 44: 1019-1023
• 4 van Rijn JC, Reitsma JB, Stoker J et al. Polyp miss rate determined by tandem colonoscopy: a systematic review. Am J Gastroenterol 2006; 101: 343-350
• 5 Skovlund E, Bretthauer M, Grotmol T et al. Sensitivity of pain rating scales in an endoscopy trial. Clin J Pain 2005; 21: 292-296
• 6 Ramakrishnan S, Yiannakou JY, Ellis WR et al. Assessment of patient pain at colonoscopy: are nurses better than endoscopists?. J R Soc Med 2004; 97: 432-433
• 7 Levin TR, Zhao W, Conell C et al. Complications of colonoscopy in an integrated health care delivery system. Ann Intern Med 2006; 145: 880-886