Intensive High-volume Bowel Cleansing Regimen Versus Low-volume Bowel Regimen in Patients With a High Risk of Poor Colonic Cleansing Following a Validated Predictive Score

This is a prospective, randomized, single-blind phase IV study in which all outpatients scheduled for a colonoscopy will be given a different bowel cleansing strategy (conventional or intensified) according to a scoring system already validated in the investigator's center, designed with variables independently associated with poor bowel cleansing, constipation, abdominal/pelvic surgery, comorbidity and to be on antidepressant treatment. According to this system, a score equal to or less than 1.225, predicts with a high confidence (negative predictive value = 88%) a suitable cleansing quality with a standard preparation protocol. Therefore, these subjects will be advised of a conventional preparation (low fiber diet the day before the examination and low volume preparation consisting of 2 L of PEG with ascorbic acid). Subjects with a score greater than 1.225 will be randomized to receive an intensive bowel preparation (low fiber diet three days prior to colonoscopy and large bowel preparation consisting of 4 L PEG with bisacodyl) or a conventional one (low fiber diet the day before the examination and 2 L of PEG with ascorbic acid). The choice of low-volume preparation as a control is supported by the absence of significant differences in quality of cleanliness in patients with a score > 1.225 among patients prepared with high or low volume and that low volume preparation appears to improve tolerance and compliance.

A researcher will offer to participate in the study to all outpatients with a scheduled colonoscopy, who meet all the inclusion criteria and none of the exclusion criteria. The researchers will explain the purpose of the study and will ask to sign the informed consent. They will give verbal and written information on the bowel preparation strategy. Thus, according to the allocation group, participants must comply with a large volume cleansing strategy or a conventional one. For patients with a low score (≤ 1.225) a conventional preparation will be recommended.

Patients must complete a baseline questionnaire at the inclusion visit and another questionnaire at the colonoscopy visit.

The hypothesis of the study is that in patients with a high risk of poor bowel preparation, the large bowel based preparation strategy is superior to the conventional bowel preparation in achieving an acceptable bowel cleansing assessed by a validated scale (Boston Bowel Preparation Score).