Surprise! Patients hit with unexpected bills after surgery

Several Democratic candidates vying for the White House this year support extending public health coverage, now reserved for the elderly and low-income, to all. [AFP/File / Guillermo Arias]

One in five Americans who undergo elective surgery receive surprise bills -- despite their insurance covering the procedure -- researchers said Tuesday, with the average debt around $2,000.

The paper, published in the Journal of the American Medical Association, illustrates how difficult it is for patients in the US medical system to know how much their bills will come to, even when they have good insurance coverage.