Angelia Fowler was surprised to learn that the debt-collection agency she says is ruining her life is owned by the hospital company that saved it.

Fowler had been sick for months in November 2015 when her son finally took her to the emergency room with what turned out to be pneumonia. She spent much of the next month in a coma in intensive care at St. Mary's Medical Center in West Palm Beach, Florida. 

The bill arrived in January. After discounts, the hospital wanted her to pay $80,770. Other bills from specialists boosted the sum she owed above six figures, enough to buy a condo in West Palm Beach. It was a sum she couldn't pay.  Millions of patients like Fowler are on the receiving end of the health-care industry's collections machine. The amount of past-due medical debt in the U.S. is about $75 billion, spread among 43 million people, according to estimates from economists at MIT, Northwestern University and the University of Chicago. About half of all collections lines on credit reports are related to medical debt, a 2014 report (PDF) from the Consumer Financial Protection Bureau showed.