Renal injuries are classified according to severity into 5 grades: Grade 1: Subcapsular hematoma and / or renal contusion Grade 2: Laceration ≤ 1 cm in depth without urinary extravasation Grade 3: Laceration > 1 cm without urinary extravasation Grade 4: Laceration involving the collecting system with urinary extravasation; any segmental renal vascular injury; renal infarction; renal pelvis laceration and / or ureteropelvic disruption Grade 5: Shattered or devascularized kidney with active bleeding; main renal vascular laceration or avulsion Diagnosis of Renal Trauma Clinical evaluation, including repeated vital sign determination Urinalysis and hematocrit (Hct) If a high-grade renal injury is suspected, contrast-enhanced CT with delayed images (done about 10 to 15 minutes after the initial study) Patients with blunt trauma who are hemodynamically stable and present with microscopic hematuria alone usually have minor renal injuries that do not require surgical repair; thus, CT is unnecessary.