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现在还是以后?切除小型结直肠息肉的策略

发布日期:2014-1-29 12:40:57 文章来源:GIE 作者次数:1789

    现在还是以后?切除小型结直肠息肉的策略

    1波兰华沙研究生院医学中心胃肠及肝脏学科

    2波兰华沙居里夫人纪念癌症中心和肿瘤学会 ,

    高效的结肠镜下息肉切除术要求在息肉切除的有效性与安全性之间取得一个平衡。尽管结肠镜下息肉切除术得到广泛使用,但还未经充分研究、优化及标准化。越是基础的问题,就越难找到解决这些问题的最好方法,且内镜师之间差异就越大。一个来自于美国胃肠病学会成员的调查显示息肉切除术所使用的辅助类型,现有设置以及粘膜下注射策略的不一致性相当大[1]。其中一个无答案的问题是,是否应该在内窥镜插入和撤出期间实施息肉切除,还是只应该在撤出期间实施。息肉切除应该在撤出时实施的观念,只是源于对内窥镜插入时的撕力造成息肉切除位点出血或者穿孔的理论恐惧。另一方面,在内窥镜插入和撤出时都实施息肉切除,可以在理论上避免撤出时再次寻找到息肉的困难,降低了息肉错过率。这样可以进一步减少息肉的变异和腺瘤检出率,从而对患者有直接影响[2]。虽然大多数内镜医师赞成只能在撤出时切除大型息肉的观点,但是关于小型息肉的切除方法仍不明确。

    对于内窥镜检查法的这个问题,wildi和其同事提供了首个单中心随机对照试验结果,试验中对比了切除10毫米或更小息肉的两种策略,即在内窥镜插入和撤出时都实施切除和只在撤出时实施切除 [3]。作者强调了该研究的三个重要发现。第一,若只在撤出时实施切除则检测到3.3%的息肉在插入和/或撤出时被漏掉了,而按规定,在插入和撤出时都实施切除,则没有遗漏。第二,结肠镜检查总时间在各研究组之间无显著差异(P= 0.176)。第三,在结肠镜检查后第一天患者自我评估的不适症状在各研究组之间无显著差异,且没有在任何一组中出现有并发症。这些研究结果使得作者建议,对于大至10mm息肉在内窥镜插入和撤出时都实施切除。但是,有一些方法缺点,使得在完全接受这个研究结论时产生了犹豫。

    真有息肉被漏掉了吗?研究中所用的“遗漏的息肉”的定义是一种误导。一般情况下,当我们提到遗漏的息肉,我们的理解是在指数结肠镜检查中完全没有看到的息肉。通常在所谓的分段说法中,只有实施了重复检查,才给给出遗漏的说法。因此在这个研究中,息肉不是被遗漏了;相反,它们在插入时被看到但撤出时没有再找到。问题是它们在撤出时为什么不找到了。答案似乎是搜索时间不够长或撤出的操作技巧并非最佳。

    此外,该研究不是专门用于测量息肉错过率的,而主要是为了检测这两种策略之间的差异,因此错过率作为该研究的主要发现,其价值有限。根据作者对错过率的定义,遗漏息肉的可能性在A(在插入和撤出时都进行息肉切除)被排除了,因而,这当然是不合理的;在该组中必定有一些息肉被遗漏了。还有息肉的位置、大小、甚至形状的评定可能在插入和撤除时是不同的,因此很难肯定在插入时看到的息肉没有在撤出时被切除。因没有使用磁内窥镜定位设备,在归类为遗漏的13个息肉中,有11个位于降乙状结肠,两组中所检测到的息肉数目相等,这样看起来我们的假定是合理的。此外,该研究原始假设,只在撤出时进行息肉切除组的结肠镜检查总时间应该相对延长了8分钟(因为再次寻找息肉的困难),而与此相反,它实际上缩短了2分钟。结合内镜医师明白该研究假设的事实,表明重新检测遗漏息肉的时间不足。另外,如果该研究旨在评估实际息肉错过率,它应该被设计成一个串联结肠镜检查研究;在第一组,应该在插入和撤除时都切除息肉,而第二组应该只在撤出时切除息肉,然后再对两个组实施一项二次结肠镜检查。

    病人对这两个程序(策略)是同等容忍?虽然从统计学角度来看,患者的不适现象在不同组之间没有显著差异(P=0.075),但是该研究还不足以显示次要终点的差异。此外,所有患者都使用了镇定剂异丙酚或咪达挫仑或/和哌替啶,且在结肠镜检查一天后用4分制口述分级评分法对不适进行评估,这可能减弱容忍度的差异。如果该研究是专门用于评价病人不适的,则应该包括一个由护士执行,采用口述分级评分法且记录镇定剂使用剂量的术内疼痛评估[5][6]

    最相关的问题之一是并发症发生率在两种策略之间是否存在差异。非系统收集从结肠镜检查开始的30天内的并发症数据,但是该研究不足以回答这个问题。可能有人认为一个30天并发症终点是不可靠的,但是实验规模没那么大。假定仅在撤出时切除最大为10mm的息肉,其引发的严重并发症发生率为0.65,那么在插入和撤出期间均进行息肉切除,这引发的并发症风险比仅在撤出时切除的风险高出三倍,每组需要1125例患者才能达到80%的效能和0.05显著性水平。

    我们认为Wildi和其同事的研究,针对应该在内窥镜插入和撤出期间,还是应该只在撤出期间切除10mm息肉的这一问题,打开了科学性讨论的大门。这种基本策略取得了微小的改进,也会对临床实践产生巨大且广泛的影响。Wildi等认为即时切除比较好,我们认为精通撤出技巧以便内镜师能够完美或者接近完美地对整个大肠表面进行检查,这要比试图迅速切除可见小型息肉要更重要的多。这样的策略使得内镜师能在结肠镜检查集中精力于快速无痛插入,之后再集中精力于完美撤出。切记在插入时行息肉切除术确实会导致注意力分散和肠道过度吹气,也会延长结肠镜检查期间的疼痛期,进而导致镇定剂使用剂量增加。

    我们需要更多的研究来解答Wildi等人的研究所发现的问题。


     

    Now or later? Strategy for removing small colorectal polyps


    M. F. Kaminski
    1, 2, J. Regula1, 2

    *                               1Department of Gastroenterology and Hepatology, MedicalCenterfor Postgraduate Education,Warsaw,Poland

    *                               2MariaSklodowska-CurieMemorialCancerCenterandInstituteofOncology,Warsaw, Poland1

    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 ofAmericanCollegeof 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 polyps10 mmor 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 to10 mmon 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 to10 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 to10 mmshould 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.

    (作者:)
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