Enough time had passed since the patient’s previous colonoscopy that she met the criteria to undergo another, said Dr. Steven Itzkowitz, a gastroenterologist at the Icahn School of Medicine at Mount Sinai in New York.

She was in “reasonably good health,” and the risks of the procedure — bleeding, reaction to anesthesia, perforation of her colon — were fairly low. But she was 85. And she would need to briefly discontinue the blood thinners she took because of the cardiac stents keeping her arteries open; doing so could increase the risks.

Had Itzkowitz and his patient faced this decision five years ago, he might have scheduled the screening “without even thinking about it,” he said.…