of the renal lesion Additionally, hematuria may be absent in up to 50% of patients with vascular pedicle injuries and in approximately one-third of patients with penetrating injuries Renal injuries have been described using different classification systems based on the clinical and radiologic assessment of the patient In 1989, the Organ Injury Scaling Committee of the American Association for the Surgery of Trauma developed an injury severity score for classification of renal trauma with minor modifications made over the years This classification system is illustrated in Figure 108.2 and is summarized below: Grade I injuries include contusions or subcapsular, nonexpanding hematomas and comprise 80% of all injuries to the kidney Grade II injuries include nonexpanding hematomas confined to the perirenal fascia (Gerota’s) or lacerations less than cm in depth without extension into the collecting system or urinary extravasation Grade III injuries include lacerations extending more than cm into the renal cortex without collecting system rupture or urinary extravasation Grade IV injuries include lacerations extending into the collecting system, lacerations of the renal pelvis, ureteropelvic junction (UPJ) disruptions, injuries to the segmental renal arteries or vein, segmental infarctions due to thrombosis, or active bleeding beyond the perirenal (Gerota’s) fascia Grade V injuries include completely shattered kidneys, avulsions of renal hilum with devascularization of the kidney, or a devascularized kidney with active bleeding Parenchymal contusions and hematomas are the most common renal injuries, accounting for 60% to 90% of all lesions from blunt trauma Lacerations account for up to 10% of renal injuries and may involve disruption of the capsule, collecting system, or both Severe injuries, such as shattered kidney or pedicle avulsions, constitute approximately 3% of renal injuries Pedicle injuries result from sheer force of the kidney with subsequent stretching of the renal vessels Initial Assessment Evaluate all injured children thoroughly using a well-established pediatric trauma protocol Assessment of the genitourinary system can be undertaken once lifethreatening conditions have been identified and the child has been resuscitated Assess for flank and/or abdominal pain and the presence of flank ecchymosis or a “seat belt sign,” since all of these findings indicate significant trauma and possible renal injury