Urgent care centers, which handle a variety of acute and severe maladies from broken bones to flu and lacerations, are proliferating nationally. The industry has grown to 8,800 urgent care centers nationwide with $13 billion in revenue. They typically require no appointments and charge prices lower than emergency rooms but higher than family doctors. The number of urgent care centers has ebbed and flowed in recent decades and is now enjoying a resurgence, said Sam Steinberg, a Florida-based independent financial consultant for the healthcare industry. The centers, he said, are taking market share. "They're skimming a lot of business from the emergency rooms and from primary care doctors,? he said. ?And they're taking away good business: middle-class people with insurance who can go where they choose to go."