Paris Hilton's baby brother got bloodied up bad. Barron Hilton was the victim of a brutal beatdown that he insists was egged on by Lindsay Lohan -- and he was injured so badly that he required hospitalization.

Quick background: Hilton attended a wild blowout party at a mansion where Lohan was staying for the Art Basel festival in Miami when he was beaten down by a gentleman on Lohan's arm. He claims that Lohan taunted him the entire time and egged the aggressor on, though she denies any involvement and claims she wasn't even at the scene when the fight went down. However, video surfaced of Hilton confronting Lohan outside of the mansion refuting her claim.

TMZ now reports that Hilton sought emergency medical treatment in Miami yesterday as a result of the injuries inflicted upon him during an assault that he claims was masterminded by the troubled redhead. Hilton had several cuts on his face and was advised to seek medical attention immediately because he was so busted up.

Hilton declined to have an ambulance take him to the hospital and opted instead for private transportation to and from the University of Miami hospital, where he was treated for his injuries and also powered through a barrage of tests, including a CT scan. No word yet on just how severe his injuries are, but his big sis Paris is mad -- she commented on the above photo, "They both will pay for what they did. No one f---s with my family and gets away with it!"