Colonic bowel prep and body mass index: does one size fit all? A multi-centre review

To investigate whether body mass index (BMI) is a risk factor for inadequate bowel preparation in elective colonoscopy. The null hypothesis being BMI does not affect bowel preparation adequacy.

A retrospective cohort study of all participants with complete medical records who had an elective colonoscopy was conducted across three tertiary teaching hospitals in Perth, Western Australia, from January 2016 to July 2019. Participants were separated into BMI subgroups of healthy weight, overweight and obese (≥ 30 kg/m²). Data were extracted from medical records, colonoscopy and histopathology reports and were analysed using SPSS v.27.

Of the 1082 cases analysed, 52.7% (n = 570) were male. The median age was 61 (range 18-85 years). The median BMI was 27.8 (range 20-52). The median procedure time is 28 (range 2-69 min). Routine follow-up was the clinical indication for 65% of colonoscopy procedures undertaken during the study period. Multivariate logistic regression, controlled for statistically insignificant confounders of age, type of bowel preparation agent, grade of the endoscopist, the indication for procedure and year of procedure, showed that being obese was significantly and independently associated with inadequate bowel preparation (OR 2.0, 95% CI (1.4-2.9) p < 0.001). Another significant factor was male (OR 1.6, 95% CI (1.2-2.1) p = 0.002).

This study shows that obese patients are more likely to have inadequate bowel preparation at colonoscopy. Given the increased complication rates and health care costs associated with repeating colonoscopies and the increased risk of colorectal cancer in obese patients, it may be worth tailoring a more extensive bowel preparation regimen to ensure adequate visualisation of the colonic mucosa on the first attempt.