(Radiographics. 2001;21:S201-S214.)
© RSNA, 2001
Helping the Trauma Surgeon |
CT Findings in Blunt Renal Trauma1
Alison C. Harris, MB, ChB, MRCP, FRCR,
Charles V. Zwirewich, MD, FRCPC,
Iain D. Lyburn, MB, ChB, MRCP, FRCR,
William C. Torreggiani, MB, ChB, MRCPI, FRCR, FFRRCSI and
Lorie O. Marchinkow, RTR
1 From the Department of Radiology, Vancouver General Hospital, 855 W 12th Ave, Vancouver, British Columbia, Canada V5Z 1M9. Presented as an education exhibit at the 2000 RSNA scientific assembly. Received February 2, 2001; revision requested April 5 and received May 10; accepted May 29. Address correspondence to C.V.Z. (e-mail: zwirecv@unixg.ubc.ca).
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Abstract
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Computed tomography (CT) can provide essential anatomic and physiologic information required to determine management of intraabdominal and retroperitoneal injuries sustained during blunt abdominal trauma. It can help in evaluation of the type and severity of parenchymal injury, the extent of perirenal hemorrhage and parenchymal devascularization, and the presence of urinary extravasation. CT can help confirm the presence of major injuries to the vascular pedicle and depict occult renal pathologic conditions. Principal indications for the use of CT in the evaluation of blunt renal trauma include (a) the presence of gross hematuria, (b) microscopic hematuria associated with shock (systolic blood pressure <90 mm Hg), and (c) microscopic hematuria associated with a positive result of diagnostic peritoneal lavage. The majority of renal injuries sustained during blunt abdominal trauma are contusions and minor parenchymal lacerations amenable to nonoperative management. Deep parenchymal lacerations, urinary extravasation, and mild to moderate degrees of parenchymal devascularization may also be treated conservatively. Radiologists should look for coexisting renal lesions such as tumors and traumatic false aneurysms that may alter management.
Index Terms: Kidney, CT, 81.12114 • Kidney, hemorrhage, 81.413 • Kidney, infarction, 81.77 • Kidney, injuries, 81.41, 81. 482
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LEARNING OBJECTIVES FOR TEST 4
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After reading this article and taking the test, the reader will be able to:
- Discuss the CT imaging findings and severity grading of renal injury due to blunt abdominal trauma.
- Identify those patients in whom renal imaging is indicated.
- Develop management strategies to deal with the range of renal injuries that may be presented.
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Introduction
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Computed tomography (CT) is widely used in the evaluation of intraabdominal and retroperitoneal injuries sustained during blunt abdominal trauma. Abdominal CT in the setting of acute trauma can provide essential anatomic and physiologic information required in determining treatment.
Renal injuries occur frequently among patients who sustain blunt abdominal trauma. Ninety-five percent of injuries are minor and can be managed without surgery (1). The presence of hematuria and hypotension are two important clinical signs associated with an increased risk of significant renal injury. Unfortunately, there is poor correlation between the severity of hematuria and severity of renal injury. Computed tomography (CT) is currently the diagnostic tool of choice for the evaluation of blunt abdominal trauma in the patient in hemodynamically stable condition. It can be used to accurately assess the severity of renal injury, determine the presence of urinary extravasation and perirenal hemorrhage, and determine the status of the renal vascular pedicle. It can also be used to identify clinically occult active renal or perirenal bleeding, as well as unsuspected structural abnormalities including tumors and congenital variants that may affect the choice of management.
This article reviews the spectrum of CT findings in patients with blunt renal trauma and current treatment guidelines for each class of injury.
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Classification of Injuries
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Renal injuries are classified into five grades of severity (Fig 1) according to the American Association of Surgeons in Trauma organ injury severity scale (Table) (2). This surgical-pathologic classification system recognizes the progressive nature of parenchymal and vascular damage associated with increasingly severe mechanisms of trauma. Approximately 82% of injuries may be classified as grade 1 and include parenchymal contusions and isolated subcapsular hematomas. Grade 2 injuries include superficial cortical lacerations less than 1 cm in depth and nonexpanding perirenal hematomas. Grade 3 injuries include lacerations greater than 1 cm in depth without extension into the collecting system or evidence of urinary extravasation. Deep lacerations that involve the collecting system, traumatic thrombosis of a segmental renal arterial branch, and injuries to the main renal artery not associated with renal devascularization are all grade 4 injuries. Grade 5 injuries, the most severe, include shattering of the kidney into multiple fragments and devascularizing injuries to the renal pedicle. They also include avulsion of the renal artery, as well as in situ thrombosis of an intact renal artery, usually due to a shearing injury to the intima. In one large urologic series, minor parenchymal lacerations (grade 2) accounted for 6% and major lacerations (grades 3 and 4) accounted for 7% of injuries. Vascular injuries (grades 4 and 5) accounted for only 5.5% of cases (3).
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Figure 1a. Graphical representation of the American Association of Surgeons in Trauma grading system: grades 1-5. (a) Grade 1: subcapsular hematoma (arrow). (b) Grade 2: superficial renal laceration (arrow) with perirenal hemorrhage (arrowhead). (c) Grade 3: deep laceration (arrows) without extension into the collecting system of the kidney. (d) Grade 4 parenchymal injury: deep laceration (straight arrows) that involves the renal collecting system (curved arrow). (e) Grade 4 vascular injury: thrombosis of a segmental renal arterial branch (arrows) with segmental renal infarction (shaded area). (f) Grade 5 parenchymal injury: multiple deep lacerations that result in a shattered kidney. (g) Grade 5 vascular injury: traumatic occlusion of the main renal artery due to intimal injury (solid arrow) with distal arterial thrombosis (open arrows). (h) Grade 5 vascular injury: renal arterial avulsion (arrow).
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Figure 1b. Graphical representation of the American Association of Surgeons in Trauma grading system: grades 1-5. (a) Grade 1: subcapsular hematoma (arrow). (b) Grade 2: superficial renal laceration (arrow) with perirenal hemorrhage (arrowhead). (c) Grade 3: deep laceration (arrows) without extension into the collecting system of the kidney. (d) Grade 4 parenchymal injury: deep laceration (straight arrows) that involves the renal collecting system (curved arrow). (e) Grade 4 vascular injury: thrombosis of a segmental renal arterial branch (arrows) with segmental renal infarction (shaded area). (f) Grade 5 parenchymal injury: multiple deep lacerations that result in a shattered kidney. (g) Grade 5 vascular injury: traumatic occlusion of the main renal artery due to intimal injury (solid arrow) with distal arterial thrombosis (open arrows). (h) Grade 5 vascular injury: renal arterial avulsion (arrow).
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Figure 1c. Graphical representation of the American Association of Surgeons in Trauma grading system: grades 1-5. (a) Grade 1: subcapsular hematoma (arrow). (b) Grade 2: superficial renal laceration (arrow) with perirenal hemorrhage (arrowhead). (c) Grade 3: deep laceration (arrows) without extension into the collecting system of the kidney. (d) Grade 4 parenchymal injury: deep laceration (straight arrows) that involves the renal collecting system (curved arrow). (e) Grade 4 vascular injury: thrombosis of a segmental renal arterial branch (arrows) with segmental renal infarction (shaded area). (f) Grade 5 parenchymal injury: multiple deep lacerations that result in a shattered kidney. (g) Grade 5 vascular injury: traumatic occlusion of the main renal artery due to intimal injury (solid arrow) with distal arterial thrombosis (open arrows). (h) Grade 5 vascular injury: renal arterial avulsion (arrow).
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Figure 1d. Graphical representation of the American Association of Surgeons in Trauma grading system: grades 1-5. (a) Grade 1: subcapsular hematoma (arrow). (b) Grade 2: superficial renal laceration (arrow) with perirenal hemorrhage (arrowhead). (c) Grade 3: deep laceration (arrows) without extension into the collecting system of the kidney. (d) Grade 4 parenchymal injury: deep laceration (straight arrows) that involves the renal collecting system (curved arrow). (e) Grade 4 vascular injury: thrombosis of a segmental renal arterial branch (arrows) with segmental renal infarction (shaded area). (f) Grade 5 parenchymal injury: multiple deep lacerations that result in a shattered kidney. (g) Grade 5 vascular injury: traumatic occlusion of the main renal artery due to intimal injury (solid arrow) with distal arterial thrombosis (open arrows). (h) Grade 5 vascular injury: renal arterial avulsion (arrow).
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Figure 1e. Graphical representation of the American Association of Surgeons in Trauma grading system: grades 1-5. (a) Grade 1: subcapsular hematoma (arrow). (b) Grade 2: superficial renal laceration (arrow) with perirenal hemorrhage (arrowhead). (c) Grade 3: deep laceration (arrows) without extension into the collecting system of the kidney. (d) Grade 4 parenchymal injury: deep laceration (straight arrows) that involves the renal collecting system (curved arrow). (e) Grade 4 vascular injury: thrombosis of a segmental renal arterial branch (arrows) with segmental renal infarction (shaded area). (f) Grade 5 parenchymal injury: multiple deep lacerations that result in a shattered kidney. (g) Grade 5 vascular injury: traumatic occlusion of the main renal artery due to intimal injury (solid arrow) with distal arterial thrombosis (open arrows). (h) Grade 5 vascular injury: renal arterial avulsion (arrow).
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Figure 1f. Graphical representation of the American Association of Surgeons in Trauma grading system: grades 1-5. (a) Grade 1: subcapsular hematoma (arrow). (b) Grade 2: superficial renal laceration (arrow) with perirenal hemorrhage (arrowhead). (c) Grade 3: deep laceration (arrows) without extension into the collecting system of the kidney. (d) Grade 4 parenchymal injury: deep laceration (straight arrows) that involves the renal collecting system (curved arrow). (e) Grade 4 vascular injury: thrombosis of a segmental renal arterial branch (arrows) with segmental renal infarction (shaded area). (f) Grade 5 parenchymal injury: multiple deep lacerations that result in a shattered kidney. (g) Grade 5 vascular injury: traumatic occlusion of the main renal artery due to intimal injury (solid arrow) with distal arterial thrombosis (open arrows). (h) Grade 5 vascular injury: renal arterial avulsion (arrow).
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Figure 1g. Graphical representation of the American Association of Surgeons in Trauma grading system: grades 1-5. (a) Grade 1: subcapsular hematoma (arrow). (b) Grade 2: superficial renal laceration (arrow) with perirenal hemorrhage (arrowhead). (c) Grade 3: deep laceration (arrows) without extension into the collecting system of the kidney. (d) Grade 4 parenchymal injury: deep laceration (straight arrows) that involves the renal collecting system (curved arrow). (e) Grade 4 vascular injury: thrombosis of a segmental renal arterial branch (arrows) with segmental renal infarction (shaded area). (f) Grade 5 parenchymal injury: multiple deep lacerations that result in a shattered kidney. (g) Grade 5 vascular injury: traumatic occlusion of the main renal artery due to intimal injury (solid arrow) with distal arterial thrombosis (open arrows). (h) Grade 5 vascular injury: renal arterial avulsion (arrow).
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Figure 1h. Graphical representation of the American Association of Surgeons in Trauma grading system: grades 1-5. (a) Grade 1: subcapsular hematoma (arrow). (b) Grade 2: superficial renal laceration (arrow) with perirenal hemorrhage (arrowhead). (c) Grade 3: deep laceration (arrows) without extension into the collecting system of the kidney. (d) Grade 4 parenchymal injury: deep laceration (straight arrows) that involves the renal collecting system (curved arrow). (e) Grade 4 vascular injury: thrombosis of a segmental renal arterial branch (arrows) with segmental renal infarction (shaded area). (f) Grade 5 parenchymal injury: multiple deep lacerations that result in a shattered kidney. (g) Grade 5 vascular injury: traumatic occlusion of the main renal artery due to intimal injury (solid arrow) with distal arterial thrombosis (open arrows). (h) Grade 5 vascular injury: renal arterial avulsion (arrow).
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Imaging Algorithm in Suspected Blunt Renal Trauma
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There is general consensus in the urologic community that the urinary tract in any patient with blunt abdominal trauma should be imaged under the following circumstances (Fig 2): (a) presence of gross hematuria, (b) presence of microscopic hematuria associated with shock (defined as systolic blood pressure less than 90 mm Hg in the field or during resuscitation), and (c) microscopic hematuria associated with a positive result of diagnostic peritoneal lavage. Renal imaging is generally unnecessary if the patient is normotensive and has only microscopic hematuria, because the risk of serious injury that needs operative management is less than 0.2% in this group (1,3–6). CT is the preferred method of investigation in the setting of acute renal trauma. The kidneys are generally assessed as part of a dedicated abdominal and pelvic trauma CT protocol that involves utilization of intravenous contrast medium (100–150 mL of a solution of 320 mg of iodine per milliliter) administered at rates of 2–4 mL/sec. A scanning delay of 60–70 seconds after injection of contrast medium ensures good enhancement of the renal parenchyma (corticomedullary phase) in most patients. Delayed scanning of the kidneys during the excretory phase is recommended if the initial CT images show a deep parenchymal laceration or large perirenal fluid collection. Excretory-phase images may be acquired 3–5 minutes after injection of contrast medium (7). Section thickness of 5–8 mm and a reconstruction interval of 2.5–4 mm are generally acceptable. CT cystography may be combined with this protocol when bladder rupture is a concern. Renal angiography and selective embolization are generally reserved for patients in hemodynamically stable or marginally unstable condition with (a) active hemorrhage detected at CT or (b) delayed hemorrhage that occurs while the patient is under nonoperative management.
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CT Features of Specific Injuries
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Contusions and Hematomas
Renal contusions (grade 1) are characterized by a focal area of decreased enhancement in the renal parenchyma relative to normal adjacent regions. Contusions may have sharply or poorly defined margins (Fig 3). They are differentiated from areas of renal infarction by the presence of contrast enhancement in the former and its absence in the latter. Subcapsular hematomas (grade 1) may vary in attenuation value as a function of the age of the clot. Acute hematomas are typically hyperattenuating (40–60 HU) relative to renal parenchyma on unenhanced CT images. When small, subcapsular hematomas appear crescentic and may exert minimal mass effect on the adjacent renal parenchyma (Fig 4). As they enlarge, theytend to assume a biconvex appearance at CT. When the renal capsule is lacerated, hematoma can enter the perinephric space (Fig 5).
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Figure 3a. Renal contusions. CT scans show poorly defined (arrow in a) and sharply marginated (arrows in b) areas of decreased parenchymal enhancement in the right kidney of two different patients with renal contusions. Perirenal hemorrhage is absent in both cases.
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Figure 3b. Renal contusions. CT scans show poorly defined (arrow in a) and sharply marginated (arrows in b) areas of decreased parenchymal enhancement in the right kidney of two different patients with renal contusions. Perirenal hemorrhage is absent in both cases.
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Figure 4a. (a) CT scan shows a hyperattenuating subcapsular hematoma (h) resulting from trauma to a clinically unsuspected lower pole renal adenocarcinoma. (b) CT scan obtained after injection of contrast medium shows the tumor (arrow).
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Figure 4b. (a) CT scan shows a hyperattenuating subcapsular hematoma (h) resulting from trauma to a clinically unsuspected lower pole renal adenocarcinoma. (b) CT scan obtained after injection of contrast medium shows the tumor (arrow).
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Figure 5a. Perirenal hemorrhage after minimal trauma in two patients with preexisting renal lesions. (a) CT scan reveals hemorrhage in a traumatized right renal cyst (solid arrow) and associated perirenal hematoma (open arrows). (b) CT scan of a different patient shows perirenal hemorrhage (h) that occurred after trauma to an occult small renal carcinoma (arrow).
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Figure 5b. Perirenal hemorrhage after minimal trauma in two patients with preexisting renal lesions. (a) CT scan reveals hemorrhage in a traumatized right renal cyst (solid arrow) and associated perirenal hematoma (open arrows). (b) CT scan of a different patient shows perirenal hemorrhage (h) that occurred after trauma to an occult small renal carcinoma (arrow).
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Lacerations
Renal lacerations appear as linear, low-attenuation areas in the parenchyma and may be superficial (<1 cm depth; Fig 6) or deep (>1 cm depth; Fig 7). Deep lacerations may spare the collecting system (grade 3) or may involve it (grade 4), which results in urinary extravasation (8,9). Lacerations generally contain clotted blood and therefore do not enhance on scans obtained after intravenous administration of contrast medium. Perirenal hematomas with attenuation values in the 45–90 HU range are common and may be large.
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Figure 6. Superficial lacerations. CT scan reveals a moderate perirenal hematoma that surrounds the posterior aspect of the left kidney (H) adjacent to two superficial lacerations (arrows).
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Figure 7a. Deep renal lacerations. (a) CT scan of one patient shows a deep laceration (open arrow) that has resulted in a large perirenal hematoma (solid arrows). (b) CT scan of another patient shows a deep, full-thickness parenchymal fracture (arrow) with only minimal perirenal bleeding. The depth of the fracture does not reliably correlate with the size of the perirenal hematoma.
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Figure 7b. Deep renal lacerations. (a) CT scan of one patient shows a deep laceration (open arrow) that has resulted in a large perirenal hematoma (solid arrows). (b) CT scan of another patient shows a deep, full-thickness parenchymal fracture (arrow) with only minimal perirenal bleeding. The depth of the fracture does not reliably correlate with the size of the perirenal hematoma.
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Active Hemorrhage and Urinary Extravasation
When intense contrast enhancement occurs within a laceration or an adjacent hematoma during the early phase of the CT examination, the diagnosis of traumatic false aneurysm or active hemorrhage should be considered (Fig 8). Active hemorrhage tends to track into surrounding tissues and has a linear or flamelike appearance, whereas false aneurysms tend to be more focal and rounded. Extravasation of vascular contrast medium appears with attenuation values of 80–370 HU, is typically within 10–15 HU of the aorta or adjacent major artery, and is generally surrounded by lower-attenuation clotted blood (10–12). This finding is an important indicator that a patient may be about to pass from hemodynamic stability to decompensation. In one series, 38% of patients with this finding became hypotensive during or immediately after the CT examination (11). Patients in stable condition withactive vascular extravasation should be referred for angiographic embolization.
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Figure 8. Active arterial hemorrhage in a patient in marginally unstable condition. CT scan reveals a serpentine collection of vascular contrast material (arrow) within a large tissue-attenuation hematoma posterior to the right kidney. The diagnosis of arterial bleeding rather than caliceal rupture with urine leakage was predicated on the patient’s clinical status and the complete absence of fluid-attenuation, unopacified urine in the perirenal space. The patient became hypotensive during CT and underwent partial nephrectomy.
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Contrast enhancement within a laceration or around the kidney during the pyelographic phase of the CT examination indicates the presence of a urine leak (Fig 9). Delayed scanning 10–15 minutes after intravenous administration of contrast medium may be useful in selected patients to show the extent of urinary extravasation (Fig 10).
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Figure 9a. Spontaneous resolution of urinary extravasation. (a) Initial CT scan shows extravasation of urinary contrast medium around the medial hilar lip of the right kidney (arrow). (b) CT scan obtained 3 days later while the patient was managed conservatively shows that the leak has closed. No urinoma was present.
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Figure 9b. Spontaneous resolution of urinary extravasation. (a) Initial CT scan shows extravasation of urinary contrast medium around the medial hilar lip of the right kidney (arrow). (b) CT scan obtained 3 days later while the patient was managed conservatively shows that the leak has closed. No urinoma was present.
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Figure 10a. Value of excretory-phase CT in the detection of urine leaks in a patient kicked by a horse. (a) CT scan shows a fractured left kidney surrounded by a large mixed-attenuation collection (arrows). It is not clear whether this collection represents hematoma or a combination of blood and urine. (b) Excretory-phase CT scan shows a large volume of urine extravasated into the perinephric space (arrow). Partial nephrectomy was required because of ongoing bleeding.
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Figure 10b. Value of excretory-phase CT in the detection of urine leaks in a patient kicked by a horse. (a) CT scan shows a fractured left kidney surrounded by a large mixed-attenuation collection (arrows). It is not clear whether this collection represents hematoma or a combination of blood and urine. (b) Excretory-phase CT scan shows a large volume of urine extravasated into the perinephric space (arrow). Partial nephrectomy was required because of ongoing bleeding.
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Renal Infarction
Thrombosis or laceration of a segmental renal arterial branch produces a focal area of renal infarction. Infarcts typically appear as peripherally based, wedge-shaped areas of parenchyma that fail to enhance during both the corticomedullary and pyelographic phases of a CT study. Segmental infarcts may be solitary or multiple and are frequently associated with other renal injuries (Fig 11). The term shattered kidney refers to gross renal parenchymal disruption by multiple lacerations; these injuries are frequently associated with multiple areas of renal infarction (Fig 12). Devascularization of the entire kidney due to laceration or to in situ thrombosis of the main renal artery constitutes the most severe form of renal injury (grade 5). Such injury may occur with or without parenchymal lacerations (Figs 13, 14). If the kidney is devascularized as a consequence of an isolated intimal injury to the renal artery that results in thrombosis, extensive retroperitoneal hemorrhage and hematuria may be absent. The classic findings of traumatic renal infarction at CT include absent nephrogram on the affected side, retrograde opacification of the renal vein from the inferior vena cava, and abrupt truncation of the renal arterial lumen at the point of occlusion (Fig 14) (13). The cortical rim nephrogram sign of a devascularized kidney (Fig 15) may be absent in the acute setting. Traumatic renal venous thrombosis is suggested by a persistent nephrogram and reduced or no opacification of the ipsilateral renal vein.
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Figure 11a. Multiple segmental renal infarcts. Late-nephrographic- (a) and excretory-phase (b) CT scans show multiple wedge-shaped infarcts in the right kidney (straight arrows). Perirenal hematoma (curved arrow in a) and urinary extravasation (curved arrow in b) are also present.
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Figure 11b. Multiple segmental renal infarcts. Late-nephrographic- (a) and excretory-phase (b) CT scans show multiple wedge-shaped infarcts in the right kidney (straight arrows). Perirenal hematoma (curved arrow in a) and urinary extravasation (curved arrow in b) are also present.
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Figure 13. Grade 5 renal vascular injury: avulsion of the renal artery. CT scan shows that the right kidney (arrows) is devascularized and surrounded by a hyperattenuating clot that extends into multiple deep lacerations in the renal parenchyma. Traumatic avulsion of the renal artery was found at nephrectomy.
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Figure 14a. Grade 5 renal vascular injury: infarcted right kidney secondary to traumatic renal arterial thrombosis. (a) CT scan shows virtually no enhancement of the right kidney, and retrograde opacification of the right renal vein is present (arrow). (b) Aortic digital subtraction angiogram shows occlusion of the renal artery (arrow). (c) Selective renal digital subtraction angiogram shows thrombus within the artery (arrow). Retroperitoneal hematoma is completely absent from this vascular injury. This finding is typical of shearing injuries to the renal artery that result in intimal disruption and in situ vascular thrombosis rather than full-thickness arterial disruption.
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Figure 14b. Grade 5 renal vascular injury: infarcted right kidney secondary to traumatic renal arterial thrombosis. (a) CT scan shows virtually no enhancement of the right kidney, and retrograde opacification of the right renal vein is present (arrow). (b) Aortic digital subtraction angiogram shows occlusion of the renal artery (arrow). (c) Selective renal digital subtraction angiogram shows thrombus within the artery (arrow). Retroperitoneal hematoma is completely absent from this vascular injury. This finding is typical of shearing injuries to the renal artery that result in intimal disruption and in situ vascular thrombosis rather than full-thickness arterial disruption.
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Figure 14c. Grade 5 renal vascular injury: infarcted right kidney secondary to traumatic renal arterial thrombosis. (a) CT scan shows virtually no enhancement of the right kidney, and retrograde opacification of the right renal vein is present (arrow). (b) Aortic digital subtraction angiogram shows occlusion of the renal artery (arrow). (c) Selective renal digital subtraction angiogram shows thrombus within the artery (arrow). Retroperitoneal hematoma is completely absent from this vascular injury. This finding is typical of shearing injuries to the renal artery that result in intimal disruption and in situ vascular thrombosis rather than full-thickness arterial disruption.
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Management Options
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Urologists have adopted a conservative management strategy for all but the most severe renal injuries. This conservatism is due to historical evidence that the nephrectomy rate is higher among patients who undergo operative exploration (35%) than among those who simply undergo observation (12.6%) (8). Radiologists must recognize that before a renal injury can be selected for nonoperative management it must be accurately imaged and staged. The only absolute indication for surgical exploration is life-threatening renal bleeding (9). Relative indications for operative management include the presence of (a) extensively devitalized tissue (>50% of the renal parenchyma), (b) urinary extravasation that cannot be controlled with conservative means such as ureteral stent placement or nephrostomy, and (c) arterial thrombosis (8,9).
Grades 1 and 2 injuries are managed nonoperatively with excellent results; patients have normally functioning kidneys at follow-up imaging (8). Most patients with injuries of intermediate severity (grades 3 and 4) also undergo nonoperative management. Urinary extravasation alone (grade 4) is not an indication for surgery, as the urine leak will spontaneously resolve in up to 87% of patients (Fig 16) (9). Careful follow-up with serial CT examinations is warranted in these patients to monitor the severity of the urine leak and to direct percutaneous drainage of any collections in patients with symptoms or sepsis. Grade 4 injuries associated with infarction of <50% of the renal parenchyma are treated conservatively unless they are accompanied by a large hematoma or urine leak, in which case surgical débridement is strongly considered. Aggressive monitoring of patients with grade 3 and 4 injuries and use of percutaneous drainage or angiographic embolization as required has reduced the laparotomy rate in this group to approximately 10% (Figs 17, 18) (9).
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Figure 16a. Conservative management of a grade 4 injury with complete healing in a patient involved in a motor vehicle accident. (a) CT scan shows a deep laceration to the posterior renal parenchyma (arrow). (b) Excretory-phase CT scan shows a large volume of urinary extravasation (arrows). The injury was treated by means of observation only. (c) CT scan obtained 9 months later shows a normal kidney with virtually no evidence of previous trauma.
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Figure 16b. Conservative management of a grade 4 injury with complete healing in a patient involved in a motor vehicle accident. (a) CT scan shows a deep laceration to the posterior renal parenchyma (arrow). (b) Excretory-phase CT scan shows a large volume of urinary extravasation (arrows). The injury was treated by means of observation only. (c) CT scan obtained 9 months later shows a normal kidney with virtually no evidence of previous trauma.
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Figure 16c. Conservative management of a grade 4 injury with complete healing in a patient involved in a motor vehicle accident. (a) CT scan shows a deep laceration to the posterior renal parenchyma (arrow). (b) Excretory-phase CT scan shows a large volume of urinary extravasation (arrows). The injury was treated by means of observation only. (c) CT scan obtained 9 months later shows a normal kidney with virtually no evidence of previous trauma.
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Figure 17a. Delayed hemorrhage from a grade 3 injury treated with subselective embolization in a patient injured in a motor vehicle accident 2 weeks prior to the CT examination. Her injuries were being treated with observation when massive gross hematuria developed and she became hypotensive. (a-c) CT scans show a deep laceration in the left kidney (arrows in a) and clots within the renal pelvis (arrow in b) and bladder (arrow in c). (d) Selective left renal angiogram shows a false aneurysm arising from an interpolar arterial branch (arrow). (e) Selective left renal angiogram obtained after embolization shows that the aneurysm was successfully embolized with coils. Renal function was preserved and partial nephrectomy avoided.
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Figure 17b. Delayed hemorrhage from a grade 3 injury treated with subselective embolization in a patient injured in a motor vehicle accident 2 weeks prior to the CT examination. Her injuries were being treated with observation when massive gross hematuria developed and she became hypotensive. (a-c) CT scans show a deep laceration in the left kidney (arrows in a) and clots within the renal pelvis (arrow in b) and bladder (arrow in c). (d) Selective left renal angiogram shows a false aneurysm arising from an interpolar arterial branch (arrow). (e) Selective left renal angiogram obtained after embolization shows that the aneurysm was successfully embolized with coils. Renal function was preserved and partial nephrectomy avoided.
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Figure 17c. Delayed hemorrhage from a grade 3 injury treated with subselective embolization in a patient injured in a motor vehicle accident 2 weeks prior to the CT examination. Her injuries were being treated with observation when massive gross hematuria developed and she became hypotensive. (a-c) CT scans show a deep laceration in the left kidney (arrows in a) and clots within the renal pelvis (arrow in b) and bladder (arrow in c). (d) Selective left renal angiogram shows a false aneurysm arising from an interpolar arterial branch (arrow). (e) Selective left renal angiogram obtained after embolization shows that the aneurysm was successfully embolized with coils. Renal function was preserved and partial nephrectomy avoided.
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Figure 17d. Delayed hemorrhage from a grade 3 injury treated with subselective embolization in a patient injured in a motor vehicle accident 2 weeks prior to the CT examination. Her injuries were being treated with observation when massive gross hematuria developed and she became hypotensive. (a-c) CT scans show a deep laceration in the left kidney (arrows in a) and clots within the renal pelvis (arrow in b) and bladder (arrow in c). (d) Selective left renal angiogram shows a false aneurysm arising from an interpolar arterial branch (arrow). (e) Selective left renal angiogram obtained after embolization shows that the aneurysm was successfully embolized with coils. Renal function was preserved and partial nephrectomy avoided.
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Figure 17e. Delayed hemorrhage from a grade 3 injury treated with subselective embolization in a patient injured in a motor vehicle accident 2 weeks prior to the CT examination. Her injuries were being treated with observation when massive gross hematuria developed and she became hypotensive. (a-c) CT scans show a deep laceration in the left kidney (arrows in a) and clots within the renal pelvis (arrow in b) and bladder (arrow in c). (d) Selective left renal angiogram shows a false aneurysm arising from an interpolar arterial branch (arrow). (e) Selective left renal angiogram obtained after embolization shows that the aneurysm was successfully embolized with coils. Renal function was preserved and partial nephrectomy avoided.
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Figure 18a. Embolization of active hemorrhage in a patient with a solitary kidney who was hypotensive with gross hematuria after blunt abdominal trauma due to a vehicular accident. (a) Selective right renal arteriogram shows a small false aneurysm in the lower pole of a hypertrophied right kidney (arrow). (b) Angiogram obtained after subselective injection shows the false aneurysm (arrow). (c) Angiogram obtained after embolization with gelatin sponge particles was used to obliterate the aneurysm and stop the bleeding. (d) Postembolization CT scan obtained without additional intravenous contrast medium shows a residual focal collection of extravasated angiographic contrast medium within a deep renal laceration (arrow). The patient remained in stable condition and recovered uneventfully.
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Figure 18b. Embolization of active hemorrhage in a patient with a solitary kidney who was hypotensive with gross hematuria after blunt abdominal trauma due to a vehicular accident. (a) Selective right renal arteriogram shows a small false aneurysm in the lower pole of a hypertrophied right kidney (arrow). (b) Angiogram obtained after subselective injection shows the false aneurysm (arrow). (c) Angiogram obtained after embolization with gelatin sponge particles was used to obliterate the aneurysm and stop the bleeding. (d) Postembolization CT scan obtained without additional intravenous contrast medium shows a residual focal collection of extravasated angiographic contrast medium within a deep renal laceration (arrow). The patient remained in stable condition and recovered uneventfully.
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Figure 18c. Embolization of active hemorrhage in a patient with a solitary kidney who was hypotensive with gross hematuria after blunt abdominal trauma due to a vehicular accident. (a) Selective right renal arteriogram shows a small false aneurysm in the lower pole of a hypertrophied right kidney (arrow). (b) Angiogram obtained after subselective injection shows the false aneurysm (arrow). (c) Angiogram obtained after embolization with gelatin sponge particles was used to obliterate the aneurysm and stop the bleeding. (d) Postembolization CT scan obtained without additional intravenous contrast medium shows a residual focal collection of extravasated angiographic contrast medium within a deep renal laceration (arrow). The patient remained in stable condition and recovered uneventfully.
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View larger version (162K):
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Figure 18d. Embolization of active hemorrhage in a patient with a solitary kidney who was hypotensive with gross hematuria after blunt abdominal trauma due to a vehicular accident. (a) Selective right renal arteriogram shows a small false aneurysm in the lower pole of a hypertrophied right kidney (arrow). (b) Angiogram obtained after subselective injection shows the false aneurysm (arrow). (c) Angiogram obtained after embolization with gelatin sponge particles was used to obliterate the aneurysm and stop the bleeding. (d) Postembolization CT scan obtained without additional intravenous contrast medium shows a residual focal collection of extravasated angiographic contrast medium within a deep renal laceration (arrow). The patient remained in stable condition and recovered uneventfully.
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Actively bleeding renovascular pedicle injuries (grade 5) may need prompt surgical exploration to prevent exsanguination (9). Traumatic thrombosis or avulsion of the renal artery must be diagnosed and treated rapidly, as permanent, progressive loss of renal function begins after 2 hours of warm-ischemia time (14). Although some authors have reported technical success in repair of arterial injuries after several hours of warm ischemia (15), most concur that repair must occur within 4 hours of injury if meaningful renal function is to be realistically expected (16). Even with reconstructive surgery, only 14%–29% of kidneys return to normal function (9,15). If renal ischemia has exceeded 4 hours and the contralateral kidney is normal, most urologists will avoid surgery and allow the devascularized kidney to atrophy. If devascularizing injuries are bilateral or involve a solitary kidney, reconstructive surgery is generally attempted even if the ischemia time has exceeded 4 hours (14,16).
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Summary
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Radiologic investigation of the kidneys in patients who have sustained blunt trauma can generally be restricted to those with systolic blood pressure less than 90 mm Hg, gross or microscopic hematuria, and a positive result of peritoneal lavage. CT is the preferred imaging method and is accurate in staging the severity of renal injuries. The majority of renal injuries are minor and need no urologic intervention. Conservative management is also possible among most patients with deep parenchymal lacerations, urinary extravasation, and mild to moderate degrees of parenchymal devascularization. Renal arterial injuries associated with devascularization of the entire kidney should be treated with prompt surgical revascularization within 4 hours of injury to minimize the risk of irreversible loss in renal function. When the diagnosis is delayed beyond this point, patients in hemodynamically stable condition with a normal contralateral kidney undergo nonoperative management. \
%Immediate laparotomy is indicated in hemodynamically unstable patients with grade 5 injuries. Angiography and selective embolization are useful adjuncts in stable patients with active bleeding at the time of initial CT or those with delayed hemorrhage while undergoing conservative management. Radiologists should carefully search for coexisting renal lesions such as tumors and traumatic false aneurysms that will affect case management. Close cooperation between the radiologist and urologist is essential in optimizing the management of blunt renal injuries and ensuring a favorable outcome.
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Acknowledgments
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We gratefully acknowledge the secretarial support of Betty Fowler in the preparation of the manuscript.
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References
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Abstract
LEARNING OBJECTIVES FOR TEST...
