Computed tomography of renal emergencies: A comprehensive diagnostic guide for radiology residents

Table 1 Grading of renal trauma

Grade	Description	Imaging findings
I	Subcapsular hematoma +/- renal parenchymal contusion without definite laceration	Contusion: Ill-defined area of hypoattenuation on nephrographic phase; hyperdense on excretory phase due to retained parenchymal contrast. Subcapsular hematoma: Iso-to-hyperdense renal subcapsular collection
II	Renal parenchymal laceration of ≤ 1 cm depth with perirenal hematoma; absent urinary extravasation	Laceration: Linear area of hypoattenuation of ≤ 1 cm in length. Perirenal hematoma: Ill-defined stranding or hyperdense collection contained within the Gerota fasci. Absent urinary extravasation on excretory phase
III	Renal parenchymal laceration of > 1 cm depth without urine extravasation, active kidney bleeding contained within Gerota fascia, renal vascular pseudoaneurysm, or an AVF contained within Gerota fascia	Laceration: Linear area of hypoattenuation of > 1 cm in length. Vascular findings contained within the Gerota fascia: Pseudoaneurysm: Focal contrast-filled outpouching. AVF: Early renal venous opacification. Absent urinary extravasation on excretory phase
IV	Parenchymal laceration extending to the renal collecting system with urine extravasation, renal pelvic laceration +/- complete ureteropelvic disruption, segmental renal vein or artery AVF or pseudoaneurysm, active bleeding beyond Gerota fascia into retroperitoneal or peritoneal cavity, segmental or complete kidney infarction due to vessel thrombosis but without active bleeding	Urine extravasation on excretory phase. Segmental vascular involvement with findings similar to grade III, however, extending beyond Gerota fascia. Wedge-shaped hypoattenuations indicating renal infarcts
V	Shattered kidney with loss of identifiable parenchymal anatomy, devascularized kidney with or without active bleeding, lacerated main renal artery or vein, or an avulsed renal hilum	Active contrast extravasation on early phase with blooming on delayed phases indicating active vascular bleeding. Extensive ill-defined renal parenchymal hypoattenuation with disrupted anatomy

AVF: Arteriovenous fistula.