Tips for Maximizing Colonoscopy Preps

David A. Johnson, MD


February 14, 2023

This transcript has been edited for clarity.

Hello. I'm Dr David Johnson, professor of medicine and chief of gastroenterology at Eastern Virginia Medical School in Norfolk, Virginia.

Colonoscopy requires preparations; yet, these don't always result in the best preparations. This is an issue that needs improvement. The adequacy of these preparations (aka, preps) is what drives utilization and what drives patients to return for subsequent colonoscopies on a quicker basis.

Alongside my colleagues Dr Doug Rex and Dr Edward Oldfield, I recently co-wrote a review paper offering best practice tips from the experts on colon preps. Today, I'd like to give you some highlights from this paper that I think you'll find quite helpful.

Safety Considerations

According to the US Multi-Society Task Force on Colorectal Cancer, bowel preparation is adequate approximately only 75% of the time. We can certainly do better, and one of the ways to do that is by tailoring the preps and using strategies to optimize success.

In our review, we discuss high/large-volume and low-volume preps, the latter of which seem to be the most popular and best tolerated by patients.

We also briefly highlight the always important issues around safety.

One thing to remember around these preps is the magnesium content of the sodium picosulfate products (ie, Clenpiq). These should be avoided in patients with advanced kidney disease, in this case, those with a glomerular filtration rate of < 30 mL/min/1.73m2, which would correspond to chronic renal disease stage 4 or 5.

In patients who have glucose 6–phosphate dehydrogenase (G6PD) deficiency, products such as MoviPrep and Plenvu contain ascorbic acid. This may increase the risk for hemolytic reaction related to the G6PD deficiency. Plenvu also has phenylalanine, which is a component of the aspartame ingredient, so it should be avoided in patients with phenylketonuria.

There are certain populations where we typically use a larger volume prep because it's more osmotically balanced and not so hyperosmotic. But, in this review, we note that our general experience has been that this is safe in the majority of patients.

You should use clinical judgment for patients with chronic renal disease, congestive heart failure, and decompensated cirrhosis as well as for those who are older and frail. In these patients, we need to look at why we're doing these procedures. Certainly, the formulations, be it a tablet or liquid, need to be adjusted to the individual circumstance.

Barriers and Special Considerations

There are a couple of things we can do to optimize bowel prep efficacy.

We can recognize things that may predict for less adequate outcomes, particularly insurance barriers, whereby you don't get to pick the prep that you'd ideally like for the individual patient.

There are also barriers related to language, low education, and health literacy. There are tools available on the websites for some of these commercial products that may be quite helpful in navigating these barriers with your patients.

For patients with a history of bariatric surgery, we always use a low-volume prep and extend the time for consumption. Such gastrointestinal surgeries in and of themselves are predictors of less adequate preps, so we need to be very careful in patients who have had bariatric surgery.

Strategies for Optimizing Success

One of the things that we find with the lower-volume preps is that patients tend to not drink ancillary fluids. Dr Rex and I routinely recommend about 2.5-3 L of fluid around the bowel prep, irrespective of what is being taken. This replenishes the effluent losses incurred by the bowel preparation.

The other issue is the timing of the preparations.

I've routinely moved my dosing much earlier in the afternoon of the day before if this works for the patients. Traditionally, patients receive instructions to begin their prep at 5:00 PM or 6:00 PM. If they work, they may still have to conform to that schedule. But it tends to drive them into effluent bowel movements throughout the night, which is very disruptive for sleep and can lead to negative feelings about how their overall prep went. As we know, patients don't remember the procedure, they remember the prep. Therefore, we can try moving that dosing earlier in the afternoon or evening to debulk some of the solid stool.

The dosing on the morning of the colonoscopy is the most important. This allows for a "runway time," which describes the typically 3-hour period between when they finish the prep to when they get their colonoscopy. Generally, they must begin their prep 4-6 hours before they're ready to come in, with it being completed within 2 hours [before the colonoscopy] to provide the standards for the American Society of Anesthesiology criteria for sedation. So look at the timing on the day of too.

Another consideration is low-fiber diets, which patients are routinely put on for 2-5 days prior to colonoscopy. It virtually never works, with almost nonexistent compliance after just 2 days. Instead, the routine use of low-residue diets has become our standard in patients who don't have predictors for poor outcomes. In practice, we do this on the morning of the start of the prep and perhaps even for lunch, followed by conversion to clear liquids at that point. There is demonstrable evidence that the odds ratios are two times greater as far as less nausea, vomiting, and hunger as well as higher ease of completion and willingness to repeat. Those are all important factors in a patient's overall satisfaction.

Another thing we recommend is to routinely look for online or discount pharmacy coupons. Many of the companies provide these and may allow you access to some of these preps that you would otherwise have thought would be too expensive for individual patients.

Summary Recommendations

We conclude our paper with some best practice recommendations, which I'd like to highlight here.

The evaluation of a bowel prep should be tailored to an individual patient and not be a routine one-size-fits-all approach. The provider should know the characteristics of these bowel preps as well as their safety characteristics. We've put together a few valuable tables on preps, both approved and not yet approved by the US Food and Drug Administration, as well as their safety considerations. I think you'll find them worthwhile for downloading and posting where you can reference them, such as in your scheduler's office.

We also discuss the volume of the bowel prep and the overall volume of fluids to be consumed. Remember that 2.5-3 L can provide adequate hydration status when these patients come in.

Split dosing the day before colonoscopy is the standard of care. Dosing can be moved back to make it more flexible. I think the patients will let you know they slept better and enjoyed the overall experience more than if they'd been up all night running to the bathroom. The last dose on the day of the procedure remains the same, to be initiated 4-6 hours before the scheduled time.

Consider the low-residue diet for part of the day before the colonoscopy. This really has become my standard, and the patients' experience is much better.

Lastly, remember these online discount coupons. These are particularly relevant for the low-volume preps that are currently available.

Hopefully these same tips will lead to better patient discussions and outcomes for when you do your bowel prep selection and instructions.

I'm Dr David Johnson. Thanks again for listening.

David A. Johnson, MD, a regular contributor to Medscape, is professor of medicine and chief of gastroenterology at Eastern Virginia Medical School in Norfolk, Virginia, and a past president of the American College of Gastroenterology. His primary focus is the clinical practice of gastroenterology. He has published extensively in the internal medicine/gastroenterology literature, with principal research interests in esophageal and colon disease, and more recently in sleep and microbiome effects on gastrointestinal health and disease.

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