Bowel Preparation for Colonoscopy in Patients with Diabetes: From a Recognized Risk Factor to Risk-Adapted Preparation

Adequate bowel preparation remains essential for high-quality colonoscopy, yet patients with diabetes mellitus consistently experience higher rates of inadequate bowel cleansing. Although diabetes is well established as a risk factor, treating it as a simple binary variable may no longer be sufficient. Diabetes is a heterogeneous disease, and the probability of inadequate bowel preparation likely varies substantially according to individual clinical characteristics. Evidence suggests that diabetes-related autonomic neuropathy may contribute to gastrointestinal dysmotility, including gastroparesis and impaired colonic transit, while chronic constipation may also arise through other mechanisms. These conditions, together with other diabetes-related complications, glycemic characteristics, medication exposure and longer disease duration, may contribute to or identify increased vulnerability to inadequate bowel preparation. Recent findings linking longer diabetes duration to clinically inadequate bowel preparation further highlight the need to investigate risk heterogeneity within the diabetic population. However, diabetes duration should be regarded as a candidate risk marker rather than a causal factor or stand-alone criterion for intensified preparation. We propose that research now move beyond repeatedly demonstrating diabetes as a risk factor and toward developing and prospectively validating diabetes-specific risk-stratification approaches. These approaches should subsequently be evaluated in intervention trials to determine whether targeted modifications of bowel preparation improve cleansing quality, metabolic safety and patient adherence. The next step is therefore not simply diabetes-specific preparation but risk-adapted preparation for patients with diabetes.