Impact of contrast extravasation on computed tomography of the psoas major muscle in patients with blunt torso trauma

BACKGROUND The clinical significance of contrast extravasation (CE) on computed tomography (CT) of the psoas major muscle after blunt torso trauma and the optimal management of patients requiring transcatheter arterial embolization (TAE) of the lumbar artery have not been well elucidated. The aim of this study was to investigate the impact of CE on CT to determine the need for TAE of the lumbar artery. METHODS We examined a single-center retrospective cohort of blunt torso trauma patients who underwent contrast-enhanced CT from 2008 to 2017. Basic demographics and clinical data were obtained, including the number of lumbar transverse process fractures (LTPFs) and maximum psoas major muscle hematoma (PMMH) size and ratio. Maximum PMMH size was analyzed by measuring the cross-sectional area of hematoma size at the level of CE. Psoas major muscle hematoma size ratio was obtained by dividing maximum PMMH size by psoas major muscle size of the unaffected side at the same slice level. RESULTS A total of 762 patients were included. One hundred seventeen patients had LTPFs and/or PMMH. Of 117 patients, 25 had CE on CT of the psoas major muscle and had significantly higher rates of older age and severe injury compared with those without CE. Of the 25 patients with CE, 13 required TAE of the lumbar artery. Patients who required TAE had a significantly higher number of LTPFs (4 vs. 2, p = 0.011) and higher PMMH size ratio (2.10 vs. 1.32, p = 0.016). Psoas major muscle hematoma size ratio revealed moderate accuracy (area under the receiver operating characteristic curve, 0.782). CONCLUSIONS Approximately half of the blunt torso trauma patients with CE on CT of the psoas major muscle will require TAE of the lumbar artery. Higher number of LTPFs and larger PMMH size can be a predictor of the need for TAE of the lumbar artery among patients with CE on CT. LEVEL OF EVIDENCE Therapeutic/care management, level IV.