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 Obtain a urinalysis in all patients with multisystem trauma or suspected isolated renal injury Management/Diagnostic Testing Hemodynamically stable patients who present with suggestive clinical findings, gross hematuria, microscopic hematuria of more than 50 RBCs/hpf, major associated injuries, or a history of significant deceleration injury should undergo radiographic evaluation Obtain a contrast-enhanced CT scan with delayed images Children who remain unstable despite resuscitative measures should undergo a one-shot IVP before emergency laparotomy Children with isolated microscopic hematuria of less than 50 RBCs/hpf not require immediate imaging These patients may be discharged and can be evaluated on an outpatient basis with CT, IVP, or ultrasound if hematuria persists However, in some pediatric trauma centers, management of these patients involves hospitalization for observation, followed by nonemergent radiographic evaluation The diagnostic performance of imaging modalities as they relate to the evaluation of renal trauma is reviewed below: Computed Tomography Contrast-enhanced CT with additional 10-minute delayed scan is the “gold standard” imaging modality for staging a stable trauma patient The delayed scan or “excretory” phase, occurs after contrast has passed into the renal pelvis and ureter, allowing better definition and evaluation of these structures Trauma patients lacking radiographic signs of renal injury who not have any perinephric, periureteral, or pelvic fluid collections not require delayed imaging per expert consensus If any of these subtle findings, especially lowdensity fluid tracking around the kidney and down the ureter, are present on the initial contrast-enhanced CT, delayed scan is indicated A UPJ or a ureteral injury can easily be missed if delayed images are not obtained The diagnostic accuracy of CT scan has been reported to be as high as 98% ( Fig 108.3 ) The ability of CT to quickly evaluate solid organ and vascular injuries has significantly improved the management of trauma Important radiologic findings that should be noted when reviewing CT for renal trauma include arterial medial extravasation of contrast, denoting a severe arterial injury; medial hematoma without arterial extravasation, often secondary to a venous injury; differential contrast uptake and excretion, which is indicative of arterial injury or thrombosis; cortical rim sign, often indicative of a main renal artery injury; degree of parenchymal laceration and involvement of the collecting system; degree of devitalized tissue; and the size and location of a perinephric hematoma or fluid collection FIGURE 108.2 Classification of renal injuries as proposed by the Organ Injury Scaling Committee of the American Association for the Surgery of Trauma ... Children who remain unstable despite resuscitative measures should undergo a one-shot IVP before emergency laparotomy Children with isolated microscopic hematuria of less than 50 RBCs/hpf not require... evaluated on an outpatient basis with CT, IVP, or ultrasound if hematuria persists However, in some pediatric trauma centers, management of these patients involves hospitalization for observation,