Berkshire Hathaway buys more shares of DaVita NEW YORK Warren Buffett's Berkshire Hathaway (BRK.A) now controls nearly 15 percent of kidney dialysis firm DaVita's (DVA) stock. Berkshire Hathaway reported its latest purchases of 179,300 shares on Tuesday. Berkshire told the Securities and Exchange Commission it now owns 13.975 million DaVita shares. That has grown significantly since Omaha-based Berkshire first disclosed owning 2.7 million DaVita shares at the end of 2011. Berkshire officials don't typically comment on these filings. Many investors who follow Buffett believe the DaVita investment was likely the work of one of Berkshire's two other investment managers, not Buffett. Denver-based DaVita runs nearly 2,000 outpatient dialysis clinics.