Genitourinary Radiology > Kidneys > Renal Trauma

Renal Trauma

Renal trauma is graded according to the American Association for the Surgery of Trauma (AAST) classification. Go to their website at for details.
  • Grade 1

    • Hematuria with normal imaging studies
    • Contusions
    • Nonexpanding subcapsular hematomas

  • Grade 2

    • Nonexpanding perinephric hematomas confined to the retroperitoneum
    • Superficial cortical lacerations less than 1 cm in depth without collecting systeminjury

  • Grade 3 - Renal lacerations greater than 1 cm in depth that do not involve the collecting system

  • Grade 4

    • Renal lacerations extending through the kidney into the collecting system
    • Injuries involving the main renal artery or vein with contained hemorrhage
    • Segmental infarctions without associated lacerations
    • Expanding subcapsular hematomas compressing the kidney

  • Grade 5

    • Shattered or devascularized kidney
    • Ureteropelvic avulsions
    • Complete laceration or thrombus of the main renal artery or vein
Renal contusion (Grade I AAST) is interstitial edema and hemorrhage as a result of a parenchymal bruise. Imaging shows an enlarged kidney with delayed pyelogram and diminished density of contrast in the calyces and ureter due to decreased function of the kidney. While isolated contusion is self-limited, it is frequently seen in the context of more sever renal injuries.


Contrast enhanced CT Scan of abdomen following motor vehicle collison (MVC) show fluid in abdomen and retroperitoneum (f) consistent with hemoperitoneum from liver and splenic lacerations (not shown here).  The left kidney shows minimal linear area of non-enhancement in the medial cortex(arrow).  This may represent a very small laceration or minor renal contusion: grade I or grade II.

Renal laceration (Grade III AAST) is a tear in the renal parenchyma that leads to a perirenal urinoma, hematoma, or both. Perinephric fluid collections or contrast extravasation are seen on imaging. If the patient is hemodynamically stable, lacerations are usually managed conservatively without surgery. If active bleeding is seen on contrast-enhanced CT, renal arteriography with embolization or surgical exploration may be warranted.


Contrast enhanced CT scan (1) and delayed images (2) through the kidneys following trauma shows an approximately 2 cm long laceration of the left medial reanl cortex (arrows) consistent with a grade III (AAST) renal laceration that does not involve the collecting system(no extravastion of urine from opacified collecting systemon delayed images).

Contrast enhanced (1)  CT scan through kidneys and Delayed (2) shows show a right upper pole renal laceration dividing the renal parenchyma in two and extending in the left upper pole collecting system.  The delayed images show no active extravasation of contrast and this patient was hemodynamically stable and therefore was managed conservatively.

Follow up CT scan several months after the trauma shows remarkable healing of left upper pole injury following conservative management.

Renal fracture (grade IV AAST) is a severe form of laceration that extends through the full thickness of the renal parenchyma, dividing the kidney into two or three segments. Hemodynamically stable patients can be evaluated with selective renal arteriography with embolization of small arterial bleeds and thus, emergency surgery may be avoided. However, most of these patients are not hemodynamically stable and emergent surgery is often indicated.

Delayed CT images following contrast show a fractured right kidney and extravasation of urine (U) into perinephric space in this patient s/p severe blunt trauma from MVC.  Notice there is contrast above the patients right diaphragm in the pleural space (P) consistent with diaphragmatic rupture and pleural urinoma.

Shattered kidney (Grade V AAST) is a severe form of fracture in which the kidney is fragmented into three or more separate segments. Patients are usually hemodynamically unstable with extensive and irreversible kidney damage. Careful attention must be paid to other abdominal organs, as the force required to shatter a kidney frequently causes injuries to the spleen, liver, and pancreas. These injuries are usually well-visualized on CT.

Traumatic pedicle injury (Grade V AAST) involves transection or dissection of the renal artery or vein. If diagnosis occurs within 3 to 6 hours of injury, surgical revascularization may be successful. However, the kidney is more often irreparable and nephrectomy is required.


CT findings include extensive perirenal hemorrhage along the course of the renal artery, delayed and diminished nephrogram, and a rim nephrogram. This latter finding results from persistent perfusion of the outer rim of the renal cortex, which is supplied by the capsular artery, an early branch of the renal artery that is rarely affected by renal artery transection. Therefore, the outer rim of the cortex will be relatively opaque compared to the remainder of the kidney.

Contrast enhanced CT through the kidneys show no ehnacement of the left renal parenchyma in a patient who sustained significant abdominal trauma resulting in a vascular pedicle injury that disrupted the renal artery resulting in a totally avascular left kidney.  Note that the left renal artery and vein are opacified (a & v) but the parenchyma of the left kidney (LK) is hypodense compared with the right kidney.  There is minimal enhancement in the left kidney's capsule from feeder vessels (different blood supply to renal capsule) but there is no significant blood flow to the left renal parenchyma.

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