Warren Buffett's Berkshire Hathaway has scored an almost $2 billion gain on DaVita stock in the past year

• Warren Buffett's Berkshire Hathaway has racked up a roughly $2 billion gain on DaVita in 12 months.
• The investor's company owns $4.8 billion worth of DaVita stock, up from $3 billion a year ago.
• DaVita has come under fire from skeptics including short-seller Jim Chanos.

Warren Buffett's Berkshire Hathaway has scored almost a $2 billion gain on DaVita stock in the past year, likely propelling the kidney-dialysis specialist into the conglomerate's 10 most-valuable portfolio holdings.

The famed investor's company holds 36.1 million shares of DaVita, giving it a 34.4% stake, a regulatory filing showed this month. DaVita's stock is trading close to a record high at $131, valuing Berkshire's position at $4.7 billion - up nearly 60% from about $3 billion a year ago.

The upshot is that DaVita probably ranks among Berkshire's 10 largest common-stock investments today, given that seven of its top 15 holdings were worth under $4.1 billion at the end of 2020.

Berkshire first invested in DaVita in late 2011, and grew its stake to 38.6 million shares by 2014. Buffett and his team didn't touch that position until last year, when they trimmed it by about 6% to its current size.

Ted Weschler, one of Buffett's portfolio managers, likely placed the DaVita bet. Weschler owned the stock at Peninsula Capital Advisors - his former hedge fund - between 2003 and 2011, when he landed the Berkshire job.

Berkshire's ownership of DaVita is notable, given the dialysis specialist's controversial relationship with the American Kidney Fund, a nonprofit organization that helps people with kidney disorders to cover their insurance premiums.

DaVita is one of AKF's biggest donors, prompting critics including short-seller Jim Chanos to accuse the company of effectively paying the fund to move patients from Medicare to commercial insurance, which is more lucrative for DaVita and generates most of its profits. The California Department of Insurance also launched an investigation into DaVita's ties to AKF last year.

"I just can't understand why Berkshire Hathaway would be promoting a company that's gaming the insurance business as much as DaVita is," Chanos said at the Delivering Alpha conference in 2019, describing it as a "very bad look" for the insurance behemoth. The Kynikos Associates boss added that he was shorting the stock.

DaVita, Berkshire, and Kynikos didn't immediately respond to requests for comment from Insider. AKF provided the following response:

"We have absolutely no influence over what health coverage our program recipients choose - that's because they apply to AKF for help affording their existing coverage. Further, federal firewalls and our own compliance program ensure dialysis providers have absolutely no say on which patients we assist.

"Our 100% needs-based program makes health care possible for individuals with very low household incomes who are fighting kidney failure. We provide premium assistance to about 75,000 patients annually, of which the vast majority are on Medicare and Medigap plans. We helped only 2,700 patients nationwide with individual market (ACA) plans in 2020."