Feast or Famine? A Move Toward Increased Patient Acceptance of Colonoscopy Preparation

The search continues for a colon-cleansing regimen that is efficacious, safe, and well tolerated, despite decades of research. In the past this research has mainly focused on which medication to give, and in what combination, with preparations being largely divided into large-volume and small-volume camps. The timing of administration of the medication then became the focus, with a general consensus that splitting the dose between the evening before and the morning of the procedure produces much better preparations.1–3 The initial focus was on efficacy, and only recently has it become more so on patient tolerance of split dosing; thus, the true effect of split dosing on patient tolerance of the preparations remains a little unclear. The effect of diet on colon-cleansing quality and tolerance has largely been ignored until recent years. Many studies on medications have not mentioned what diet patients were instructed to follow, or they used different diets between comparison groups4 when the intervention was something else, thus bringing ambiguity into any conclusions reached. Patient education is another growing field of research for colon cleansing, and the effect of these potential diet liberations on it remains to be determined. We found in our study5 that the low residue breakfast groups tended to call in more often with follow-up questions regarding foods not on the list, and that patients tended to go beyond the study cutoff of 11 AM for solid food by various amounts. Studies specifically looking at diet have been published more recently. Although Park et al6 carried out a very sound study, a couple of elements of their research make relating it to North American clinical practice challenging. All patients in the diet group received specific prepackaged meals, and the preparation medications were administered in their entirety the day of colonoscopy, with the colonoscopy being performed in the afternoon. Other studies have looked at the effect of fiber supplementation,7 with clear conclusions that lowering the fiber content in the days preceding colonoscopy improves prep quality. In this issue of the journal, Stolpman et al8 investigate the effect of diet on colon-cleansing quality. In brief, they randomized 201 patients to either clear liquids the day before colonoscopy (control group) or a low residue breakfast and lunch followed by clear liquids the rest of the day (intervention group). Sodium sulfate (Suprep) was used for all patients, administered in a split dose manner. On using the Boston Bowel Preparation Score (BBPS)9,10 as their primary outcome, no clinically or statistically significant differences were seen in the quality of colon cleansing, and minimal differences were observed in patient tolerance of the regimens, with more bloating in the low residue diet group and the clear liquid group experiencing slightly more hunger. The study was well conducted and had a noninferiority design, which is appropriate for a question such as this, where the primary outcome has to remain cleansing quality when one is trying to improve tolerance. Rex11 recently suggested that these trials almost always include the “best” patients, and thus perhaps noninferiority is not good enough when applied in a more general population and we should be aiming for equivalence studies. Although equivalence studies require very large numbers of patients, they certainly are possible given the number of colonoscopies performed in North America each year. However, moving from superiority studies to noninferiority is certainly a step in the right direction and the authors deserve credit for this. Another approach to offset this study bias would be a more general inclusion criteria, with elderly and constipated patients being welcomed into the trials. As seen in this study, the use of the BBPS in colon-cleansing research is becoming more common. I have some concerns with this. The scale is really best suited as a quality control measure, as it assesses the quality of mucosal visualization after all intraprocedural washing has been completed. In an extreme sense one could spend an hour washing and suctioning to clean the bowel, and if the final product is a clean colon then the BBPS score would be very good and misrepresentative of the efficacy of the preparation itself. However, its increased use is probably more reflective of the lack of alternatives. The Ottawa scale12 was useful but is hampered now by the use of foot pedal washers, which makes washing the bowel lining a matter of course in today’s colonoscopies. Stolpman and colleagues tried to offset this by measuring the BBPS both on insertion and on withdrawal, as well as going through an intense pretrial training phase in an attempt (a successful one) to ensure agreement between raters. Although not validated, this approach seems to make sense, and in this study they saw a difference in prewashing and postwashing scores in both groups, as one would logically expect, but no difference between groups, a testament to the noninferiority of the intervention. Another potential limitation of the study, as acknowledged by the authors, is the choice to have only 3 of the available 11 colonoscopists participate in the study. These 3 appear to be very high-quality endoscopists, with adenoma detection rates of >50% and relatively long (>16 min) withdrawal times. When operating at such a high end of the quality spectrum already, the ability to see change is hampered. Seeing the effect of the diet liberalization in the overall group practice would be an interesting next step. Lawrence C. Hookey, MD, FRCP(C) Department of Medicine, Division of Gastroenterology, Queen’s University, Hotel Dieu Hospital, Kingston, ON, Canada

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