When an incidental MRI finding becomes a clinical issue : Posterior lumbar subcutaneous edema in degenerative, inflammatory, and infectious conditions of the lumbar spine.

BACKGROUND: On magnetic resonance imaging (MRI), posterior lumbar subcutaneous edema (PLSE) is a frequent incidental, yet unclear finding within the deep subcutaneous perifascial tissue. This study aimed to investigate PLSE in various pathological lumbar conditions. METHODS: This retrospective study included the MR images of the lumbar spine of 279 patients (age range 18-82 years) without cardiovascular, renal or hepatic diseases, 79 of whom had low-grade disc degeneration, 101 combined endplate and facet joint degeneration, 53 axial spondyloarthritis and 46 infectious spondylodiscitis. There were 232 patients with a body mass index (BMI) <30, and 47 with a BMI ≥30 (obese). For each group, the relationship between PLSE and BMI was analyzed using multiple logistic regression, and between PLSE extension and BMI using ordinal regression. RESULTS: A PLSE was found in 11/79 (13.9%) patients with disc degeneration, 37/101 (36.6%) with endplate and facet joint degeneration, 7/53 (13.2%) with spondyloarthritis, and 28/46 (60.9%) with spondylodiscitis. For each group, a statistically significant relationship was demonstrated between PLSE and BMI (P = 0.000-P = 0.031), except for spondylodiscitis (P = 0.054), as well as between PLSE extension and BMI (P = 0.000-P = 0.049). A PLSE was found in 21.1% of nonobese and 72.3% of obese patients (P = 0.000). CONCLUSION: The presence of PLSE seems to be associated with various lumbar conditions, particularly in obese patients. Its perifascial location may suggest a potential fascial origin; however, PLSE should not to be confused with posttraumatic, postsurgical or infectious edema or edema associated with internal diseases.