Colonoscopy is a vital procedure used for both diagnosing and treating abnormalities in the lower gastrointestinal (GI) tract, as well as for colorectal cancer screening. While essential for overall health, colonoscopy preparation presents unique challenges for people with diabetes (PWD). PWD face an increased risk of adverse events during the peri-colonoscopy period, including hypoglycemia, lactic acidosis, diabetic ketoacidosis, and acute kidney injury. These risks often stem from inadequate dietary modifications, the bowel preparation process itself, and alterations in antihyperglycemic agent (AHA) regimens.
With a growing number of new diabetes medications available, it's crucial for endoscopists and PWD to have access to updated guidance on safely navigating colonoscopy preparation. This article provides a comprehensive guide to ensure a safer colonoscopy experience for individuals with both type 1 and type 2 diabetes mellitus.
The Need for Updated Guidance
Diabetes is a common condition associated with colorectal neoplasia, yet colonoscopy tends to be less effective in PWD. Furthermore, PWD face a higher likelihood of complications, including perforation and AHA-associated issues. Given the increasing prevalence of diabetes-with estimates suggesting that 10% to 20% of patients undergoing colonoscopy have diabetes-and the surge of new diabetes medications, updated guidance is essential.
Several factors contribute to the complexity of colonoscopy preparation for PWD:
- Suboptimal Bowel Preparation: PWD are more likely to experience inadequate bowel preparation.
- Metabolic Disturbances: Fasting-mediated water and electrolyte imbalances can occur.
- Medication Management: Complications can arise from inappropriate dose adjustments of AHAs.
The rise of open-access colonoscopy, where patients don't have a pre-colonoscopy appointment with the endoscopist, further exacerbates these risks. Without a proper pre-assessment, preparation and risk evaluation may be insufficient. Moreover, outdated recommendations to cease all AHAs on the day of the procedure or to hold oral AHAs during the clear fluid diet phase can be dangerous, given the risk profiles of newer AHA classes.
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Key Components of Colonoscopy Preparation for PWD
Preparation for colonoscopy in PWD typically involves a combination of dietary modification, large bowel lavage, medication management, and glucose monitoring.
Dietary Modifications
Specific dietary recommendations are crucial for effective colonoscopy preparation, but they present unique challenges for PWD. Standard recommendations often include a clear fluid diet starting the day before the procedure or a low-fiber breakfast followed by a clear fluid diet if the procedure is in the afternoon.
Challenges and Recommendations:
- Hypocaloric Diet Risks: Clear fluid diets, if low in calories, can lead to electrolyte imbalances and DKA, potentially causing AKI.
- Importance of Glucose Intake: PWD should consume fluids high in glucose during the clear fluid stage to maintain normal glucose levels. Aim for 45 g of carbohydrates for meals and 15 to 30 g for snacks, along with fluids containing electrolytes.
- Consider a Normal Breakfast: A normal breakfast the day before starting clear fluids may improve bowel preparation adequacy and tolerability compared to a full-day clear fluid diet.
What You Can Eat/Drink:
- Acceptable Foods: Honey, flavored gelatin (no red, purple, or orange), clear broth, popsicles, and hard candy. NO solid foods the day before.
- Acceptable Drinks: Lemonade, Sprite/7 Up, and water. Drink at least 12 tall glasses (8-10 ounces each) of clear liquids throughout the day in addition to the bowel prep.
- Avoid: Dark beverages (coffee, cola), and alcohol.
Bowel Preparation (Lavage)
High-quality bowel cleansing is paramount for accurate diagnosis and safe colonoscopy procedures. Inadequate cleansing can lead to cancellations, repeat procedures, longer procedure times, increased complication risks, and missed lesions.
Key Considerations:
- Split-Dose PEG: The recommended bowel preparation in Ontario for all patients with diabetes mellitus is polyethylene glycol (PEG) with or without bisacodyl, administered in a split-dose fashion. The second dose should be taken 4 to 6 hours before the procedure.
- Diabetes as a Risk Factor: Diabetes is a known predictor of inadequate bowel cleansing, potentially due to diabetic neuropathy, constipation, decreased colonic motility, and slower gastric emptying.
- Diabetes-Specific Protocols: Modifications to improve bowel preparation include adding lubipristone to PEG, adjusting AHA use, delaying the clear fluid diet to 8 hours before colonoscopy, and providing a specific low-residue diet plan in the days leading up to the procedure.
Medication Management: Antihyperglycemic Agent (AHA) Adjustments
PWD are at risk of glucose disturbances during the peri-colonoscopy period, necessitating careful adjustment of AHAs and close blood glucose monitoring. Recommendations vary depending on the specific AHA class and its half-life.
General Principles:
- Hypoglycemia Risk: AHAs, particularly insulins and insulin secretagogues, carry a risk of hypoglycemia. Patients must be educated on the signs and symptoms.
- Hyperglycemia Risk: Prematurely stopping or decreasing AHA doses can lead to hyperglycemia, dehydration, metabolic decompensation, osmotic diuresis, and AKI.
Specific AHA Recommendations:
Metformin: Stop when the clear fluid diet begins. Metformin is renally excreted, and dehydration during colonoscopy prep can increase the risk of lactic acidosis.
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GLP-1 Receptor Agonists (GLP-1 RAs): Stop when the clear fluid diet begins. Resume at the normal dose once meals resume. For once-weekly injectables, hold the dose if it's scheduled within two days before colonoscopy. GLP-1 RAs can cause GI side effects like nausea and delayed gastric emptying.
DPP-4 Inhibitors: These generally have few adverse effects but accumulate in patients with renal insufficiency.
SGLT-2 Inhibitors: Stop starting 3 days before colonoscopy, regardless of when the clear fluid diet begins. These have a diuretic effect and can increase the risk of dehydration and DKA. Note that SGLT-2 inhibitors can cause euglycemic DKA.
Insulin Secretagogues (Sulfonylureas and Meglitinides): Meglitinides should be stopped when the clear fluid diet begins. Sulfonylureas should be stopped starting the full day before colonoscopy due to the risk of hypoglycemia.
Insulin: Insulin dosing must be reduced or omitted before colonoscopy.
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- Rapid- and Short-Acting Insulins: Decrease normal doses by 50% once the clear fluid diet begins. If dosing based on insulin-to-carbohydrate ratio, continue typical rapid-acting insulin dosing.
- Intermediate-Acting and First-Generation Basal Insulins: Take 80% of the normal dose the full day before the procedure and 50% the morning of the procedure.
- Second-Generation Basal Insulins: People with type 1 diabetes should take 50-80% of their normal dose, and people with type 2 diabetes should take 50% of their normal dose, both starting the day before the colonoscopy.
- Premixed Insulin: Reduce doses by 50% at breakfast and dinner the day before colonoscopy.
- Insulin Pumps: Reduce the basal insulin rate to 80% of the normal rate once the clear fluid diet begins. Consider using the exercise setting on automated insulin delivery systems.
Once meals and adequate hydration have resumed, all insulins should be resumed at the normal dose and interval.
Glucose Monitoring
Regular blood sugar monitoring is essential during colonoscopy preparation. On preparation day and the morning of your colonoscopy, make sure to check your blood sugar if you feel that it may be too high or too low.
Recommendations:
- Frequent Monitoring: If you don't have a continuous glucose monitor, plan to take your blood sugar meter and test strips with you to the test.
- Addressing Low Blood Sugar: Note, if you experience low blood sugar (<60) during the 2 hours before your procedure, you can take 3 teaspoons of soda or clear juice to raise your sugar.
- Communicate with Your Doctor: Please call your physician if you have any questions or if you are having difficulty with the preparation.
General Instructions and Important Considerations
- Medication Awareness: Make your nurse or doctor aware if you are taking blood thinners like Eliquis®, Warfarin, Xarelto®, Plavix, Coumadin®, Heparin, Pradaxa® or Iron.
- Early Scheduling: When scheduling your colonoscopy, schedule your appointment early in the day.
- Carbohydrate Intake: Work with your diabetes doctor on how best to manage carbohydrates as you prepare for the test. Plan 45 grams of carbohydrate for liquid "meals" and 15 to 30 grams for snacks.
- Clear Liquid Diet: Follow a clear liquid bowel cleansing regimen the day before your procedure. Replace your usual meals with 45 to 60 grams of liquid carbohydrates on preparation day and incorporate sugar-free liquid options.
- Resuming Medications: You can resume eating a regular diet after you’ve recovered from the anesthesia. Once you have started eating regular food, it is OK to restart your home medication schedule.
Types of Colonoscopy Prep
The primary purpose of colonoscopy prep is to clean out the bowels of stool and undigested material. The clearer the area, the better doctors can visualize potential concerns. Colonoscopy prep involves taking an oral laxative, which triggers a bowel movement to clean out the bowel. A laxative stimulates bowel movements and draws more water into your stools from your intestines.
There are two primary types of oral laxatives for colonoscopy prep:
- Polymer-based formulas
- Saline-based formulas
Both types contain electrolytes to help prevent dehydration.
Colonoscopy Bowel Prep Instructions
Preparing for your colonoscopy starts several days before your procedure. The first two days are spent eating a low-fiber diet to prepare your digestive system. You need to follow a clear liquid diet for the entire day before your procedure. On the evening before your colonoscopy, you begin the laxative. At least half of the bowel prep will need to be ingested five hours before the time of the procedure on the day of the procedure. Most laxatives take between three and six hours to trigger bowel movements, but it varies.
The Importance of Communication and Education
Effective colonoscopy preparation for PWD hinges on clear communication and comprehensive patient education.
- Discuss Medications: The doctor doing your colonoscopy (gastroenterologist) will want to know about all the medicines you take. Be sure to also tell your doctor about any vitamins, supplements, and herbal remedies you take.
- Ask Questions: It’s important to talk with your doctor if you don’t understand what to do with your medications.
- Address Concerns: We realize our patients with diabetes may be wondering about the safety of a colonoscopy prep. The bottom line is it can be done safely if you follow our instructions.
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