UPDATE 1-Tenet posts bigger-than-expected loss on weak patient volumes

(Adds details, shares)

Aug 7 (Reuters) - For-profit U.S. hospital operator Tenet Healthcare Corp slashed its full-year forecasts on Monday and reported a bigger-than-expected quarterly loss, hurt by softer patient volumes.

Growing uncertainty amid Republicans' persisting efforts to repeal and replace former President Barack Obama's signature healthcare law, formally known as the Affordable Care Act, has weighed on hospital operators who had for long benefited from the expanded insurance coverage under Obamacare.

Tenet now forecasts full-year adjusted earnings per share from continuing operations between 69 cents to 99 cents, from $1.05 to $1.30, forecast earlier.

Net loss attributable to the company's shareholders widened to $55 million, or 55 cents per share, in the second quarter ended June 30, from $46 million, or 46 cents per share, a year ago.

Excluding items, the company reported a loss of 17 cents per share, compared with analysts' average estimate of a loss of 16 cents, according to Thomson Reuters I/B/E/S.

Net operating revenue fell to $4.80 billion from $4.87 billion, missing estimates of $4.90 billion.

Shares of the Dallas-based company were down 4.9 percent at $15.94 in after-hours trading. (Reporting by Divya Grover in Bengaluru; Editing by Shounak Dasgupta)