A continuing debate on 6-minute withdrawal time as a quality indicator during colonoscopy

We read with interest the article by Moritz et al. [1], which concluded that a 6-minute withdrawal time should not be used as an indicator of quality or as a surrogate end point for adenoma detection rate in colonoscopy. This conclusion was drawn because no difference was found in the adjusted odds ratios for the detection of polyps (≥ 5 mm) for endoscopists with a median visual withdrawal time (VWT) of ≥ 6 minutes compared with endoscopists with a median VWT of < 6 minutes.

It is apparent that polyps are missed, as colorectal cancers develop in many patients even after surveillance colonoscopy. One of the most important determinants of the polyp detection rate (PDR) has been reported to be the overall withdrawal time (OWT) [2] [3]. In these studies, an OWT of 6 minutes was reported as a quality indicator for an endoscopist to have a good adenoma detection rate. In the Moritz study, the authors evaluated PDR with regard to median VWT and overall withdrawal time (OWT) [1]. They noted that a 6-minute cut-off did not predict a better PDR with regard to VWT, but the PDR was noted to be better in cases with an OWT of ≥ 6 minutes. However, it is not clear from the text whether the higher PDR in the group with OWT ≥ 6 minutes was not simply due to increased OWT itself. On the contrary, Table 2 of the paper indicates that there was only a relative increase in the PDR for endoscopists with an OWT ≥ 6 minutes, most probably due to the transfer of most of the patients with polyps into this group. In reality, it would be more correct to define the PDR in the OWT groups as the number of additional polyps detected just after starting polypectomy or by subtracting the number of polyps detected during OWT from the number of polyps seen during VWT.

We believe that rather than withdrawal time, the technique adopted by the endoscopist is of the utmost importance in increasing PDR during colonoscopy. A well-trained endoscopist looks carefully at the entire colonic mucosa including areas behind colonic folds, maneuvering the colonoscope so that areas are examined from all angles. The use of a retroflexed colonoscope results in a higher PDR, especially at the cecum and ascending colon. It is also very important to concentrate on the procedure and reach the cecum as quickly as possible. It has been shown that a longer time to reach the cecum is associated with a higher miss rate of colonic polyps [4]. Use of a Third Eye Retroscope (Avantis Medical Systems, Sunnyvale, California, USA) and the warm water insufflation method also help to improve the PDR during colonoscopy [5] [6].

Thus, there are so many parameters that contribute to a high PDR during colonoscopy and withdrawal time is possibly one of them. However, we believe that the 6-minute cut-off does not increase the PDR during a carefully performed colonoscopy procedure.

• References

• 1 Moritz V, Bretthauer M, Ruud HK et al. Withdrawal time as a quality indicator for colonoscopy – a nationwide analysis. Endoscopy 2012; 44: 476-481
• 2 Imperiale TF, Glowinski EA, Juliar BE et al. Variation in polyp detection rates at screening colonoscopy. Gastrointest Endosc 2009; 69: 1288-1295
• 3 Taber A, Romagnuolo J. Effect of simply recording colonoscopy withdrawal time on polyp and adenoma detection rates. Gastrointest Endosc 2010; 71: 782-786
• 4 Kim JH, Kim YS, Cheon JH et al. Influence of the insertion time and number of polyps on miss rate in colonoscopy. Scand J Gastroenterol 2011; 46: 634-639
• 5 Leufkens AM, van Oijen MG, Vleggaar FP, Siersema PD. Factors influencing the miss rate of polyps in a back-to-back colonoscopy study. Endoscopy 2012; 44: 470-475
• 6 Leung JW, Do LD, Siao-Salera RM et al. Retrospective analysis showing the water method increased adenoma detection rate – a hypothesis generating observation. J Interv Gastroenterol 2011; 1: 3-7