ABSTRACT
Background and study aims: Obesity is a recognised risk factor for poor bowel preparation in retrospective studies whilst corresponding data in prospective trials are marginally reported. Aims are to evaluate the relation between body mass index [BMI] and preparation quality in retrospective and interventional prospective settings and within a single centre
Patients and methods: Data from a recent colorectal cancer screening registry were retrospectively analysed for the relation between BMI and adequacy of preparation. Patients were categorised as underweight [BMI < 20 kg/m2], normal [20-25 kg/m2], overweight [25-30 kg/m2], and obese [>30 kg/m2]. Data from a recent prospective colon preparation trial were similarly analysed
Results: 541 registry patients were included. Multivariate analysis showed BMI to be an independent risk factor for inadequate preparation. Obesity was associated with odds ratio [OR] of 5.3 [95% confidence interval [CI] 1.4-19.8; p = 0.01] compared to normal BMI. A significant difference was also noted in underweight but otherwise healthy individuals [OR = 11.1, 95% CI 2-60; p = 0.005]. In the prospective study of 195 patients, obese patients had comparable rates of inadequate preparation to normal-weight individuals [OR = 0.7, 95% CI 1.1-3.96; p = 0.68]. Underweight patients had a significantly worse preparation compared to normal BMI individuals [OR = 8, 95% CI 1.1-58; p = 0.04]
Conclusions: In real life, bowel preparations in obese individuals have a lower quality in comparison to normal individuals. This finding is not replicated in clinical trials. This discrepancy is likely the result of focused patient education suggesting that this is primarily a dietary compliance phenomenon. Underweight individuals appear to have worse quality of preparation independent of study design or setting