Tenet Healthcare reported a surprise quarterly profit on Monday, as the hospital operator benefited from lower costs and a jump in patient visits partly due to the severe flu season.

The company also raised its full-year earnings forecast, sending its shares up about 5 percent to $25.19 after the bell.

Tenet in December added another $100 million to its $150 million annual cost cut targets as the company looks to pare its long-term debt of $14.22 billion as of March 31.

Operating costs in the first quarter ended March 31 fell 8 percent to $4.21 billion.

Like other hospital operators, Tenet also gained from one of the most severe flu seasons in the United States.

Tenet said on Monday same-facility revenue grew 11.8 percent in the non-surgical business, reflecting strong growth in urgent care visits.

The company raised its 2018 earnings forecast to $1.36 to $1.70 per share, from 73 cents to $1.07 previously expected.

Sales in the company's Conifer division, which it plans to sell, rose marginally to $404 million.

Net profit attributable to Tenet's common shareholders was $99 million, or 96 cents per share, in the quarter, compared with a net loss of $53 million, or 53 cents per share, a year earlier.

Excluding items, Tenet reported a profit of 57 cents per share, beating analysts' average estimate of a loss of 3 cents, according to Thomson Reuters.

Net operating revenues fell to $4.70 billion from $4.81 billion.