Gene Simmons has been battling with painful kidney stones.

Gene Simmons

Gene Simmons

The KISS rocker underwent an hour-long non-invasive procedure at Cedars-Sinai Hospital on Tuesday (01.10.19) to remove the stones, which are are caused by crystals that collect inside the kidneys and form a stone-like lump, from his body.

A source told TMZ that the 70-year-old musician had a stent inserted through his urethra which ultimately forced the stones to pass from his kidney to his bladder.

It's believed the stent will be removed in a weeks' time and any remaining stones, which most often affect people aged 30 to 60, will be removed then too.

Last month, Gene told fans that he was postponing his gig in Salt Lake City while he "takes care" of his health and undergoes a medical procedure in Los Angeles.

He tweeted at the time: "Apologies to the fans in Salt Lake City. We will come back and do the show at a later date.

"The truth is, I have to fly to LA to do a medical procedure. Nothing serious. But it must be taken care of now. Thank you for your good wishes. All is well. (sic)"

This isn't the first time Gene has suffered with kidney stones as back in 2009 he raised $15,000 for charity after he auctioned off a stone on eBay.

He said: "I passed a kidney stone and I put it on eBay for charity. $15,000."

It's not known if Gene is planning to auction off his most-recent kidney stones.

Meanwhile, his minor health battle comes less than a year after he was accused of inappropriately touching a woman's vagina during a photo opportunity at one of his Rock & Brews restaurants in 2016.

The woman - who took action under the anonymous alias of Jane Doe - was working as a dishwasher in the eatery when the rocker paid a visit and his manager and her co-workers encouraged her to take a photo with him.

The alleged victim claimed Gene's manager told her to move closer to him and when she did, the 'Crazy Crazy Nights' hitmaker allegedly "reached over and forcefully placed his hand on her vagina completely covering it."

She also accused Gene of acting in a "sexually charged" manner towards other women during the visit, touching their hands and encouraging them to unbutton their shirts.

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