American Association for the Surgery of Trauma Grade 4 Renal Injury Substratification Into Grades 4a (Low Risk) and 4b (High Risk)

Purpose: We identified computerized tomography findings associated with the need for urgent intervention for hemostasis after traumatic renal injury to update and refine the American Association for the Surgery of Trauma Organ Injury Scale for renal trauma. Materials and Methods: We retrospectively reviewed the records of consecutive patients presenting to our level I trauma center from 1999 to 2008 with American Association for the Surgery of Trauma grades 3 and 4 renal injury. In all patients initial abdominal computerized tomography was done soon after presentation to the emergency department before renal intervention. All images were interpreted by a staff radiologist and urologist blinded to clinical outcomes. Novel radiographic features (perirenal hematoma size, intravascular contrast extravasation and renal laceration site) were analyzed and correlated with the invasive intervention rate to control life threatening bleeding. Results: Of 299 patients hospitalized with renal injury 102 met study inclusion criteria. Increased perirenal hematoma size (perirenal hematoma rim distance greater than 3.5 cm), intravascular contrast extravasation and a medial renal laceration site were important radiographic risk factors significantly associated with intervention for bleeding after renal trauma. Analyzing these radiographic characteristics collectively showed that patients with 0 or 1 risk factor were at 7.1% risk for intervention and those with 2 or 3 were at remarkably higher risk, that is 66.7% (OR 26.0, 95% CI 7.20-93.9, p <0.0001). Conclusions: On radiography a large perirenal hematoma, intravascular contrast extravasation and medial renal laceration are important risk factors associated with the need for urgent hemostatic intervention after renal trauma. Assessing these computerized tomography characteristics collectively shows that American Association for the Surgery of Trauma grade 4 renal injuries can and should be substratified into grades 4a (low risk) and 4b (high risk).