Post written by Antonio Mendoza Ladd, MD, from the Division of Gastroenterology, Texas Tech University Health Sciences Center, El Paso, Texas, USA.

The primary aim of this study was determining if adding simethicone (SIM) to 4 L polyethylenglycol (PEG) preparation improved our ADR. Secondary aims included its effect on procedure times, Bubble and Boston Bowel Preparation Scale scores, and intra-procedure use of SIM. Two arms were compared, PEG vs PEG+SIM.

It has been previously reported that this intervention improves preparation quality, but its impact on ADR remains inconclusive. Interestingly, studies from China have recently reported a significant increase in their ADR by adding SIM to their preparations, but their study population included mostly diagnostic procedures. Therefore, we felt that evaluating the effect of this intervention on ADR in an average risk population undergoing regular screening for CRC was worth pursuing. Furthermore, there has been a recent association between the use of SIM through the endoscope and multi-drug resistant bacterial infection outbreaks. Thus, we hypothesized that by adding SIM to the PEG preparation, the use of intra-procedure SIM would in turn decrease.

Figure 1. The Boston Bowel Preparation Scale. A, 0 = Unprepared colon segment with mucosa not seen because of solid stool that cannot be cleared. B, 1 = A portion of mucosa of the colon segment can be seen, but other areas of the colon segment are not seen well because of staining, residual stool and/or opaque liquid. C, 2 = A minor amount of residual staining is present as well as small fragments of stool and/or opaque liquid, but the mucosa of the colon segment is seen well. D, 3 = The entire mucosa of the colon segment is seen well, with no residual staining, small fragments of stool, or opaque liquid. The wording of the scale was finalized after we incorporated feedback from 3 colleagues experienced in colonoscopy.

We did not find significant differences between the 2 groups in ADR (33.3% vs 38.8%; P = 0.881) or procedure times (759.3 ± 253.1 seconds vs 800.2 ± 459.6 seconds; P = 0.373).  However, intra-procedure use of SIM as well as the bubble scale score were significantly lower in the PEG+SIM arm (1.6% vs 48.9%; P ≤ .05) and (0.1 vs 2.1; P ≤ .05), respectively. The inter-observer agreement for the preparation scores was strong (bubble scale score kappa = .537; P < .05; BBPS score kappa = .184; P <.05). With this study we established that although SIM improved visibility during colonoscopy, it did not necessarily translate into a higher ADR. Although it was a secondary aim, the significant reduction in the intra-procedure use of SIM became our most important finding because of its infection risk reduction implications. Given that ours was a single-center study, larger multi-center trials should be done to establish if we can generalize our findings.

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