Bowel preparation for colonoscopy in diabetic patients

We thank Dr. Panarese for the comments on our manuscript on bowel preparation for diabetic patients [1].

Dr. Panarese proposes the administration of pyridostigmine as a strategy to improve bowel preparation in diabetic subjects with late complications of diabetes or constipation that may be caused by autonomic neuropathy.

Autonomic neuropathy has been associated with poor bowel preparation in diabetic patients in an observational study, although the authors did not adjust their results for confounding variables such as comorbidities, functional status, or constipation [2]. In our study, we did include data on late complications of diabetes, such as history of retinopathy and nephropathy, but there were no data on the presence of autonomic neuropathy as this is not a standard test and therefore, it was not available for many patients. It might be expected that those with other microangiopathic complications of diabetes were more likely to have autonomic neuropathy. Nevertheless, in our trial the only independent predictors for poor bowel preparation were the use of a conventional bowel preparation regimen and an impaired performance status.

The causes of poor bowel preparation can be classified into two main categories: cognitive factors related to patient compliance, such as poor comprehension or motivation to finish the preparation, and factors related to impaired bowel peristalsis, such as chronic constipation, severe comorbidity, or the secondary effects of drugs [3]. Our proposed intervention was mainly focused on improving the cognitive factors of bowel preparation through educational intervention, and a sensible and understandable diabetes-specific dietary plan, but it is also possible that a solid-food diet may achieve better bowel peristalsis than a strict clear-liquid diet.

The rationale for using pyridostigmine as an adjuvant to improve bowel preparation in diabetic patients comes from a well-designed, but small sample, clinical trial with selected participants [4]. In this trial, pyridostigmine accelerated colonic transit and improved bowel function in diabetic patients with chronic constipation. Current guidelines do not include recommendations on the use of drugs that improve motility because the use of prokinetics, such as metoclopramide, domperidone, cisapride, and tegaserod, has not improved the quality of bowel cleansing in clinical trials [5].

Our multifactorial approach reduced the rate of inadequate bowel preparation from 20 % to 7 %, which is in accordance with the standards proposed by current guidelines for the frequency of inadequate preparation ( < 15 %) [5]. Our proposed bowel preparation strategy achieved this goal in a group of patients at high risk of inadequate preparation. It should be emphasized that most of the patients in the intervention group that did not achieve adequate bowel preparation had impaired functional status, severe comorbidities, or were receiving drug treatments that could have contraindicated the use of pyridostigmine. On the other hand, some patients with constipation or late complications of diabetes were able to achieve good bowel cleansing without any adjuvant therapy.

We believe that other strategies for bowel preparation, like the use of pyridostigmine, should be reserved for patients who are adherent to the proposed bowel preparation protocol but cannot achieve adequate bowel cleansing. To date, there is insufficient evidence to recommend any salvage strategy for those patients [5] and a controlled clinical trial with pyridostigmine would be necessary to ascertain the usefulness of this strategy.

• References

• 1 Alvarez-Gonzalez M, Flores-Le Roux JA, Seoane A. et al. Efficacy of a multifactorial strategy for bowel preparation in diabetic patients undergoing colonoscopy: a randomized trial. Endoscopy 2016; 48: 1003-1009
• 2 Ozturk NA, Gokturk HS, Demir M. et al. The effect of autonomous neuropathy on bowel preparation in type 2 diabetes mellitus. Int J Colorectal Dis 2009; 24: 1407-1412
• 3 Dik VK, Moons LMG, Hüyük M. et al. Predicting inadequate bowel preparation for colonoscopy in participants receiving split-dose bowel preparation: Development and validation of a prediction score. Gastrointest Endosc 2015; 81: 665-672
• 4 Bharucha AE, Low P, Camilleri M. et al. A randomised controlled study of the effect of cholinesterase inhibition on colon function in patients with diabetes mellitus and constipation. Gut 2013; 62: 708-715
• 5 Johnson DA, Barkun AN, Cohen LB. et al. Optimizing adequacy of bowel cleansing for colonoscopy: recommendations from the US Multi-Society Task Force on Colorectal Cancer. Am J Gastroenterol 2014; 109: 1528-1545