The 25-year-old Geordie made a typically aggressive start on Saturday night, but was hurt by body punches as his 17-fight unbeaten record was ended by two scores of 116-112 for Patera, and the other judge gave it 116-112 to Ritson at the Metro Radio Arena.
Roared to the ring by a raucous noise, Ritson was eager to impress his local support, pumping out a stiff jab that pushed Patera into reverse in the opening round.
Ritson resumed his assault in the second, drawing blood from the nose of his opponent, who sought refuge on the ropes before firing back with crisp punches.
Cutting off the ring with ruthless intent, Ritson thudded shots into the ribs of Patera in the third, but the Belgian did land a few eye-catching combinations in the fourth.
A cluster of punches from Patera in the fifth seemed to stall Ritson, who responded with a hurtful hook in the sixth.
But Ritson was visibly troubled at the end of the seventh following a succession of stinging punches from Patera, with the bell bringing a welcome reprieve for the hometown man.
Ritson would be shaken again when they stood and traded in the eighth, and the Tyneside man tried to fend off Patera with his jolting jab in the ninth.
Another determined assault from Patera left Ritson on the brink in the 10th as he nearly wilted on the ropes following a string of body shots.
Back came Ritson in the 11th, displaying grit while unloading his right hand, but Patera ended on a high as he pumped out punches until the final bell.