Shares of dialysis chains dropped Friday on news that CMS is investigating whether third parties are steering patients from Medicaid and Medicare toward private exchange coverage. Commercial plans might pay thousands of dollars more than Medicare and Medicaid for each dialysis session, according to a lawsuit filed by UnitedHealthcare. Shares of Davita dropped from $67.7 at the market's close on Thursday to below $65 on Friday, and shares of Fresenius fell from $46.4 to below $44, after which they rebounded...