MR imaging of the lumbar spine: relation of posterior soft-tissue edema-like signal and body weight.

Abstract

Our purpose was to determine the association between posterior lumbar spine subcutaneous edema, fluid collections, and body weight on lumbar spine MR imaging. MR images of the lumbar spine obtained at 1.5 T of 307 consecutive outpatients (191 female, 116 male) were reviewed on the basis of MR imaging signal characteristics for the presence, degree, size, and location of presumed subcutaneous posterior soft-tissue edema and fluid collections. The patients were divided into three weight groups (<70, 70-85, or > 85 kg) and two age groups (<50 or >/=50 years old). Edema was graded on a scale of 0-5 according to its length relative to the vertebral bodies. When present, the fluid collection volumes were calculated. The vertical epicenter of the signal abnormality was noted by vertebral body level. Lumbar soft-tissue edema was seen in 121 patients (39%), and discrete fluid collections were seen in 53 patients (17%). Both degree of edema and volume of fluid collection were associated with increasing weight (p < 0.001 and p = 0.002, respectively) and increasing age (p < 0.001 and p = 0.01, respectively). The degree of edema in females was significantly greater than in males (p = 0.003). However, the sex of the patient did not correlate with frequency of fluid collections (p = 0.12) or volume of collections (p = 0.08). The mean epicenters of edema in females and males were at similar levels (L3.4 and L3.9, respectively, p = 0.54). The severity of posterior lumbar subcutaneous edema and the volume of fluid collections on MR imaging are associated with increased weight.