In one study, researchers found that more than three-fourths of colonoscopes and gastroscopes were still contaminated after cleaning and disinfection in accordance with manufacturer guidelines.

This new study focused on more widely used colonoscopes and gastroscopes, which have simpler designs and tend to be easier to disinfect.

The rules also do not cover cystoscopes, used to examine the bladder, and gastroscopes, used to look inside the stomach.