Aim of this study is to assess the effectiveness of O2-O3 percutaneous chemiodiscolysis by evaluating volumetric changes in lumbar disc herniation on magnetic resonance imaging, in order to identify possible pre-treatment factors affecting such changes Methods: Between January 2014 and December 2017, a total of 87 patients with low back pain and 103 lumbar disc herniations with MRI confirmation were considered for O2-O3 chemiodiscolysis. The volume of each herniated disc was determined before and after the treatment