Seven of 10 patients live in fear of medical bills they can’t afford and get by surprise, a recent survey found. Patients said they worry about such charges more than they do about putting food on the table or keeping a roof over their heads. And 4 in 10 said they experienced this nightmare because they were hit with a big, unexpected medical expense in the last year.

Bills of any kind can be displeasing. But medical bills have a special capacity to outrage...