Erik Menendez In Hospital For Kidney Stones, May Not Return To Prison

Erik Menendez is not in prison right now ... he is in a nearby hospital being treated for kidney stones, and it's possible he will not return ... sources with direct knowledge tell TMZ.

We broke the story ... Erik is being treated with what his lawyer Mark Geragos called a "serious medical condition." We have confirmed that the condition is kidney stones.

The California Department of Corrections and Rehabilitation confirms Erik was transported to an outside medical facility Friday ... and we're told he is currently in fair condition.

Our sources say California Governor Gavin Newsom is currently reviewing Erik's change in medical condition to determine if a "prison furlough" is appropriate.

It's unclear how long such a furlough would last ... it could be only until the kidney stones pass, but because Erik's upcoming parole hearing is only a month away, Newsom could cut Erik a major break where he would not have to return to prison pending parole board review.

Erik and Lyle Menendez are scheduled for a parole board hearing August 22 ... and Newsom has indicated he's sympathetic to granting both Erik and Lyle clemency.