DaVita Inc , the biggest U.S. operator of dialysis clinics, said its third-quarter profit rose 13 percent, meeting Wall Street estimates, as treatment volumes increased.

The company reported net income attributable to DaVita of $135.4 million, or $1.42 a share, compared with $119.4 million, or $1.15 a share, a year earlier.

Excluding one-time items, Davita earned $1.45 per share, matching the average analyst estimate, according to Thomson Reuters I/B/E/S.

Net operating revenue rose nearly 10 percent to $1.81 billion. Analysts had expected $1.78 billion.

DaVita said it still expects full-year operating income of $1.125 billion to $1.155 billion in 2011 and $1.2 billion to $1.3 billion in 2012.

Shares of DaVita, which rose 4.8 percent to close at $73.52 in regular trading, were slightly lower at $73.46 after hours.