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What Patient Factors Affect Bowel Preparation for Colonoscopy?

Bowel preparation is suboptimal for about one third of adults older than 55 undergoing outpatient colonoscopy, says the March issue of Clinical Gastroenterology and Hepatology. Diabetes and low level of patient engagement in their own health care contribute to less-than-optimal preparation, the researchers show.

Colonoscopy is an important screening tool for colorectal cancer, but its effectiveness requires sufficient detection of adenomas, which depends on the skill of endoscopists and the quality of bowel preparation. Suboptimal quality of bowel preparation can cause endoscopists to miss adenomas, increasing procedure times and the need for repeat examinations. It also increases a patient’s risk for developing colorectal cancer.

Many studies have compared different specific bowel preparation regimens, but few have examined patients’ roles in bowel preparation and colonoscopy quality.

Marina Serper et al. investigated the relationship between health literacy, patient engagement, and bowel preparation quality.

They analyzed results from 462 adults who received outpatient colonoscopies, 55–74 years old, and found that 134 had suboptimal quality of bowel preparation (about one third). After adjusting for demographics and clinical characteristics, diabetes increased risk for inadequate bowel preparation almost 2.5-fold.

Furthermore, Serper et al. found that a low level of patient-reported knowledge, skills, and confidence for self-management of chronic disease (called ‘patient activation’) increased risk for inadequate preparation 2-fold. Serper et al. explain that patients with low levels of activation do not possess the skills or knowledge to actively manage their health.

The authors conclude that a patient’s level of engagement in their personal health is an important factor in colonoscopy preparation. However, because this was a cross-sectional study, they warn that they cannot clearly establish the causes of inadequate cleansing.

Patients with higher levels of activation are more engaged in healthy behaviors, more likely to seek health information and ask questions, and more likely to undergo age-appropriate cancer screening. Low activation has been linked to higher healthcare costs. Health insurers have therefore begun to identify individuals with low levels of activation who could require additional counseling and support.

In an accompanying editorial, Douglas Rex explains that there are 2 sets of factors that affect the quality of bowel cleansing. One set includes medical factors (such as diabetes) which physicians can easily identify. The other includes factors that affect the ability of patients to follow the preparation instructions. He says it would helpful to develop simple surveys for use in endoscopy units to identify these patients. More work is needed to establish tools and techniques to educate and improve adherence to instructions.


Rex also explains that bowel preparation efficacy is also reduced when the cleansing agent is poorly tolerated and cannot be fully ingested. Less efficacious preparations are unsafe, because they impair adenoma or cancer detection and necessitate early repeat procedures. Poorly tolerated preparations reduce patients’ willingness to repeat procedures, reducing efficacy and safety, with regard to cancer prevention.

Interestingly, Serper et al. found that level of health literacy did not affect quality of bowel preparation for colonoscopy, and that health literacy and patient activation do not correlate. They explain that although health literacy (a measure of cognitive skill) and patient activation (a measure of patient engagement) are each associated with health behavior, they are complementary—each captures a unique yet often unmeasured patient trait.

Prospective studies of a diverse population are needed to confirm the relationships between these factors and adequate bowel cleansing. However, interventions to improve colonoscopy quality should consider the importance of patient activation in their design.

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Erin Landis

Erin Landis

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About The Author:

Dr. Kristine Novak

Dr. Kristine Novak

Dr. Kristine Novak is a science writer and editor based in San Francisco. She has extensive experience covering gastroenterology, hepatology, immunology, oncology, clinical, and biotechnology research discoveries.

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