Democrats have long been trying to stop the proliferation of doctor-owned hospitals, saying they drive up costs by encouraging doctors to order more procedures. Now Democrats in Congress are moving to impose new restrictions on these hospitals, but they have carved out exemptions for a few institutions represented by influential senators and well-connected lobbyists. The special treatment for a handful of hospitals has drawn criticism from conservative Republicans, who support unfettered growth of doctor-owned hospitals, and liberal Democrats who favor rules with no exceptions.