A novel, laser-based virtual scale endoscope might provide a solution to the ongoing problem of polyp mismeasurement. The virtual tool outperformed biopsy forceps and an endoscopic ruler for estimating polyp size in a simulated colonoscopy study.

Current Approaches Not Ideal

Because colorectal polyps can be tricky to measure due to their small size, variable shape and the limitations of a scope, endoscopists often have to make visual estimates, comparing the polyp with the known size of biopsy forceps, noted to Roupen Djinbachian, MD, who presented the study at Canadian Digestive Diseases Week 2023. Endoscopic rulers, another method used to measure polyps, are awkward and may add to colonoscopy time, said Dr. Djinbachian, a gastroenterologist at Montreal University Hospital Center. “The virtual-scale endoscope was developed to allow for superimposing a virtual scale instantaneously at the push of a button.”

To test the tool, Dr. Djinbachian and his co-investigators recruited six endoscopists to perform 60 measurements each: 20 with biopsy forceps, 20 with an endoscopic ruler and 20 with the virtual-scale endoscope. One of the researchers created polyps out of modeling clay in sizes ranging from 1 to 40 mm and shapes typically encountered during a colonoscopy and placed them in cylindrical plastic tubing that mimicked the colon.

“The virtual-scale endoscope had significantly higher relative accuracy in measuring polyp sizes compared to endoscopic rulers and forceps,” Dr. Djinbachian told Gastroenterology & Endoscopy News.

The relative accuracy was 78.9% for biopsy forceps (95% CI, 76.2%-81.5%), 78.4% for endoscopic rulers (95% CI, 76.0%-80.8%) and 82.7% for virtual-scale endoscope (95% CI, 80.8%-84.8%). The virtual-scale endoscope was more accurate than biopsy forceps (P=0.02) and endoscopic rulers (P=0.006).

All methods misclassified polyps that were actually larger than 5 mm as 5 mm or smaller, but this percentage was lowest with the virtual-scale endoscope (9.4%), followed by biopsy forceps (15.7%) and endoscopic rulers (20.9%). A similar pattern was seen in misclassification of polyps that were 20 mm or larger as being less than 20 mm (8.3%, 66.7% and 75.0%, respectively). For polyps 10 mm or larger, 22.5%, 25.5% and 25.6% were misclassified as less than 10 mm by virtual-scale endoscope, biopsy forceps and endoscopic rulers, respectively.

In the study, about one in four polyps 10 mm or larger were measured as less than 10 mm. Mismeasurement can “lead to significant delays in follow-up colonoscopies and potentially higher rates of colorectal cancer,” said Dr. Djinbachian, because post-screening follow-up intervals are based on polyp histology and size.

The findings are encouraging, said Aasma Shaukat, MD, MPH. “Multiple studies have shown that endoscopists are very poor at sizing polyps. There’s also very little correlation between different endoscopists in terms of sizing, so we’ve been searching for solutions to size polyps better,” said Dr. Shaukat, the director of outcomes research in gastroenterology and hepatology at NYU Grossman School of Medicine, in New York City.

“This is a device that points a laser that then projects a scale on the screen next to the polyp, so you can literally see the size next to a scale, which seems very promising. Obviously, the next step is larger-scale validation in actual patients and actual colon polyps, to see if it performs the same or better,” Dr. Shaukat said.

Clinical Benefits of Better Sizing

Dr. Shaukat told Gastroenterology & Endoscopy News that greater refinement of measurements could have important clinical implications. “If we had a correct size, perhaps we could get even more refined in our [recommended screening] intervals. Right now, we give ranges of three to five, or five to 10 [years]. We could start getting more precise, which would benefit the field in general,” she said.

Improved size estimation could also help refine polyp removal technique. “We’ve now developed a lot more understanding of resection techniques for polyps, and we are starting to understand different techniques to use for different-sized polyps,” Dr. Shaukat added. Better sizing estimates could help endoscopists determine “the right technique for the right polyp, including [determining if a polyp is] too large to attempt to take out and is best left to a specialist or referred to a surgeon.”

—Jim Kling

Drs. Djinbachian and Shaukat reported no relevant financial disclosures.