Inclusion Criteria:  ≥15 years of age Trauma resulting in grade III or higher splenic injury on contrast-enhanced CT Splenic injury to be treated by non-operative management as decided by attending trauma surgeon and interventional radiologist The attending interventional radiologist determines that the patient will undergo proximal splenic artery embolization with the specific method to be decided by randomization.  Exclusion Criteria:  Inability to obtain informed consent ≤ 50kg Uncorrectable coagulopathy Patient is immunocompromised Pregnant Breast-feeding Non-English speakers Prisoners