Introduction
Bowel cleansing is required prior to colonoscopy in order to optimise mucosal visualisation. Diabetes is associated with a higher risk of colorectal cancer but also poorer bowel preparation quality with colonoscopy¹. No studies, to date, have examined for a relationship between bowel preparation quality, using the Boston Bowel Preparation Scale [BBPS], and glycemic control. We examined the BBPS and glycemic control in our cohort of patients with diabetes who underwent an elective outpatient colonoscopy.

Methods
Patients with diabetes who underwent an elective outpatient colonoscopy at Christchurch Hospital, New Zealand, between 1^st January 2022 and 30^th June 2023, were retrospectively identified.

Patients included in the analysis had: HbA1c of ≥48 mmol/mol at any time prior to colonoscopy; HbA1c test performed within two months preceding or following the colonoscopy in question; outpatient colonoscopy with the local standard bowel preparation regimen (two sachets of Glycoprep® (70g) dissolved in two litres of water and consumed at 5pm the day before the colonoscopy, and one sachet of Glycoprep® (70g) dissolved in one litre of water and consumed at 5am the day of the colonoscopy).

Patients excluded in the analysis had: had a colonoscopy performed within the preceding two years; had prior gastrointestinal surgery or altered gastrointestinal anatomy; had not had BBPS not documented in the endoscopy report.

Electronic record platforms, ProVation® and Eclair clinical information system, were used for data collection. GraphPad Software was used for statistical analyses.

Results
169 patients were identified who met the inclusion criteria.

Demographics:
Median age (Interquartile range [IQR]) was 68 years (59.5 - 73) and female to male ratio was 65:104. Median (IQR) HbA1c level was 55mmol/mol (47 - 64mmol/mol).

Complete and incomplete procedures:
Eleven patients (6.5%) had incomplete procedures due to poor bowel preparation quality and had a total BBPS of zero. In contrast, completed procedures (93.5%) had a lower median (IQR) HbA1c level (54mmol/mol (47-63.25) vs 62 mmol/mol (54-93), P= 0.026.

Glycaemic control and BBPS:
When considering total or segmental BBPS, higher HbA1c was associated with lower BBPS (see Figure 1 and 2).

Conclusion
Poor glycemic control in patients with diabetes is associated with increasingly inadequate bowel preparation quality and failed procedures. BBPS is more likely to be inadequate in patients with an HbA1c above 90mmol/mol. Endoscopy units should consider dedicated or personalised education and extended bowel preparation in such patients to avoid missed lesions and reduce costs related to repeat procedures.

References
1. Chirila A, et al. Preparing for Colonoscopy in People with Diabetes: A Review with Suggestions for Clinical Practice. J Can Assoc Gastroenterol. 2022 Dec 30;6(1):26-36.

Figure 1. Table showing higher HbA1c is associated with lower, segmental or total, BBPS

Figure 2. Graph showing higher HbA1c is associated with lower total BBPS

Jack Ye

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