Buckley JC, McAninch JWJ Trauma 2011;70:35–7Expert's summary:A review of the large renal trauma database from San Francisco General Hospital (San Francisco, CA, USA) was performed with the goal of updating the existing American Association for the Surgery of Trauma (AAST) renal trauma grading system to make it more compatible with contemporary management protocols . Improvements in computed tomography (CT) imaging have been particularly important in directing the shift from the surgical management of renal injury to a mostly conservative management, and the changes proposed by Buckley and McAninch reflect both the significant improvements in imaging technology and the resulting contemporary understanding of the natural history of renal trauma.
No changes were proposed for grade 1 (renal contusion), grade 2(<1cm laceration), or grade 3(>1cm laceration without collecting system injury) renal trauma. The most significant changes were made regarding grade 4 injuries, which now comprise all collecting system injuries, including ureteropelvic junction (UPJ) injury of any severity and segmental arterial and venous injuries, which had not been previously classified. Grade 5 injuries, which before had included “shattered kidneys,” loosely meaning multiple grade 4 renal injuries in the ipsilateral kidney and complete UPJ disruption, now include only renal hilar injuries, including thrombotic events. Using this new grading system, the authors then regraded all of their 3580 renal trauma cases and found statistically similar numbers of grade 4 and 5 injuries as well as nephrectomy and renal salvage rates.Expert's comments:The changes made by the authors represent a welcome modification to the existing AAST grading scale that was adopted in 1989 . Although the current AAST grading scale has been validated to predict outcomes such as mortality and the need for nephrectomy , many authors have acknowledged that the current scale does not adequately classify certain subtypes of injuries within grades 4 and 5, specifically segmental vascular injury, and outcomes differences within each grade have been shown to exist  and . Experience with renal trauma since 1989 has taught us that renal hilar injuries more often than not need to be managed surgically, whereas most injuries involving the renal parenchyma and/or segmental vessels can safely be managed conservatively. The new scale is a product of this interval clinical knowledge and should be a more useful tool with modern CT imaging when predicting the need for surgical intervention. Its simplicity should also facilitate needed clinical study of conservative management protocols and the utility of angioembolization for renal trauma.