DaVita shares soared Wednesday after California voters rejected a ballot measure that would have capped the amount of money dialysis providers in the state can earn on certain patients.

Sixty-one percent of voters said "no" to Proposition 8 in Tuesday's midterms.

Pushed by the Service Employees International Union, the measure would have limited the revenue dialysis providers could earn through rates from privately insured patients to 115 percent of the costs to provide the care. Anything above would be put to dialysis providers, which would be forced to give insurers or patients rebates to make up the difference.

"We are grateful that Californians voted down Proposition 8," DaVita said in a statement Wednesday, "It's disappointing that the SEIU-UHW used the ballot initiative process as leverage in pursuing their own objectives, despite the potential harmful consequences to nearly 70,000 California dialysis patients."

Warren Buffett's Berkshire Hathaway owns a 23 percent stake in DaVita, which saw its shares rise more than 9 percent in premarket trade Wednesday. The stock was up more than 10 percent by midmorning.

The Denver-based company, which operates half of all the chronic dialysis clinics in the state, had shelled out $66.6 million of the more than $110 million spent by the industry lobbying against Proposition 8.

DaVita operates 292 clinics in California and more than 2,500 clinics nationwide. It reported revenue of more than $2.8 billion in the second quarter.

In a statement Wednesday, the SEIU said DaVita and the dialysis industry used "massive spending to scare and mislead Californians; imagine if that money had been spent to improve conditions in the clinics instead."

"To protect their outrageous profits, the dialysis corporations spent more than $111 million to defeat Prop. 8, the most ever spent to defeat a ballot initiative in U.S. history," the SEIU said.