Vida Guerra -- Emergency Boob Surgery But the Rack Is Intact

Model Vida Guerra -- famous for her backside -- had emergency surgery on her other money-maker yesterday -- replacing a breast implant that was creating a serious health crisis ... TMZ has learned.

Vida posted a pic of her exposed chest Tuesday morning ... showing her right breast covered by a large gauze pad. The problem was scar tissue forming around a gel implant.

Vida tells us back in 2011 she replaced saline implants with fancy new gel ones -- 450cc (or a full C cup). When she recently started having back pain and trouble breathing ... docs told her scar tissue had formed and had to be removed, along with the implant itself.

Vida got a new left implant during her 24 hour hospital stay -- but she's home now, doing something she never gets to do ... PIG OUT!!!

The fitness fanatic confesses she's been eating "everything in sight" ... especially pizza. Docs have cleared her to start working out again in a month.

Boob job lesson of the day: Vida says, "If I could do it over again, I wouldn't have. It's just more problems in the end."

And the front.