Carbon dioxide insufflation improves adenoma detection rate in colonoscopy

The move from air to carbon dioxide insufflation during colonoscopy will increase adenoma detection rates as well as reducing abdominal pain, endoscopists in Victoria have shown.

In a review of clinical outcomes for 1147 procedures carried out at three endoscopy centres in Victoria, adenoma detection rates were found to be 15.16% with air insufflation and 20.19% with carbon dioxide insufflation.

The improvement in adenoma detection rate with carbon dioxide insufflation was likely due to a more moderately distended colon achieved with carbon dioxide  insufflation and decreased need for luminal decompression compared to air insufflation, according to the researchers led by Dr Chris Mills, a gastroenterologist at the Austin Hospital, Melbourne.

“Longer time of inspection of a moderately insufflated colonic segment is more likely to reveal a mucosal abnormality such as an adenoma,” they write in the Journal of Clinical Gastroenterology.

“Equally a more moderately distended colon may explain the failure to find a difference within the polyp detection rate as diminutive hyperplastic polyps would be less obvious and the surface pattern would be more easily interpreted purely based on the endoscopic appearance.”

The findings were obtained from procedures done by four experienced endoscopists in patients over 50 years of age for a variety of indications including screening colonoscopy, polyp surveillance, follow up of FOBT positive tests and unusual bowel symptoms.

Almost half the procedures (44.3%) were done with air insufflation and 55.7% with carbon dioxide insufflation.

Polyp detection rate (PDR) was similar between the two methods (33.46% vs 35.05%), which according to the researchers indicates that PDR may not be an adequate proxy marker of adenoma detection rate. There was also a trend towards increased detection of right sided polyps in the carbon dioxide group.

The researchers say the increased detection rate will lead to shortened surveillance  intervals from 10 to five years for the additional 5% of patients in whom adenomas were detected.

The higher detection rate comes on top of the known benefits of carbon dioxide insufflation on level and duration of abdominal pain, abdominal distension and analgesic requirements, they add.

“If not already considered a standard practice for colonoscopy, carbon dioxide should now be considered the primary method of insufflation for colonoscopy. Guidelines from the relevant societies and colleges should now reflect this change in performance of insufflation method,” they suggest.

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