Lower Urinary Tract Trauma

Trauma background

• Leading cause of death in US population aged 1-44
• Injuries are frequently classified as blunt vs. penetrating due to differences in management and outcomes
  • Blast injuries may be associated with both penetrating and blunt trauma, and are most common in the setts of violent conflict
• Urologic organs are involved in ≈10% of abdominal traumas

Renal Trauma

Epidemiology

• Most commonly injured GU organ in trauma

Pathogenesis

• Kidneys are particularly prone to deceleration injuries (e.g. falls, motor vehicle collisions) because they are fixed in space only by the renal pelvis and the vascular pedicle
• The pediatric kidney is believed to be more susceptible to trauma
  • Mechanisms owing to a decrease in the physical renal protective mechanisms found in children (4):
    1. Immature, more pliable thoracic cage
    2. Weaker abdominal musculature
    3. Less perirenal fat
    4. Sits in a lower abdominal position

Diagnosis and evaluation

History and physical exam

History

• Most important information in blunt renal injury is the extent of deceleration involved in high-velocity impact trauma
• Trauma to the anterior axillary line is more likely to damage important renal structures such as the renal hilum and pedicle compared to the posterior axially line, which more commonly results in parenchymal injury

Physical exam

• Findings indicating possible renal injury (5):

1. Flank hematoma
2. Abdominal or flank tenderness
3. Rib fractures
   • Ipsilateral rib fracture can increase the incidence of significant renal trauma by 3x
4. Penetrating injuries to the low thorax or flank
5. Hematuria
   • The degree of hematuria and the severity of the renal injury do not consistently correlate; presence or absence of hematuria should not be the sole determinant in the assessment of a patient with suspected renal trauma

Imaging

• Indications
  • AUA: indications for imaging (contrast enhanced CT with immediate and delayed films) in stable trauma patients (5):
    1. Gross hematuria
    2. Microscopic hematuria and systolic blood pressure < 90mmHG
    3. Mechanism concerning for renal injury (e.g., rapid deceleration, significant blow to flank)
    4. Physical exam findings concerning for renal injury (e.g. rib fracture, significant flank ecchymosis)
    5. Penetrating injury of abdomen, flank, or lower chest
    • Generally, children can be imaged using the same criteria as adults. Children, however, often do not exhibit hypotension as adults do.
  • Campbell’s indications for imaging (similar to AUA indications but worded differently)
    1. All blunt trauma with gross hematuria
    2. All blunt trauma with microhematuria and hypotension (defined as a SBP <90 mm Hg at any time during evaluation and resuscitation)
    3. All blunt trauma with significant acceleration/deceleration mechanism of injury, specifically rapid deceleration as would occur in a high-speed motor vehicle accident or a fall from heights
    4. All penetrating trauma with a likelihood of renal injury (abdomen, flank, or low chest entry/exit wound) who are hemodynamically stable enough to have a CT (instead of going right to the operating room or angiography suite)
    5. All pediatric patients with greater than 5 RBCs/HPF

• Modality
  • CT abdomen/pelvis with IV contrast (with immediate and delayed images) should be performed when there is suspicion of renal injury (AUA)
    • In children, ultrasound may be used, although CT is preferred
    • An intraoperative one-shot IVP (2 mL/kg IV bolus of contrast with a single image obtained 10-15 minutes later) may be used to confirm that a contralateral functioning kidney is present in rare cases where the patient is taken to the operating room without preliminary CT scan if surgeons are considering renal exploration or nephrectomy
    • Major limitation of CT scan in renal trauma: inability to adequately define a renal venous injury adequately.
      • A medial hematoma strongly suggests a venous injury, however, there is no imaging modality which can accurately diagnose a venous injury

• CT findings suspicious for significant renal injury include (6):
  1. Medial laceration
  2. Medial hematoma (vascular pedicle injury)
  3. Medial urinary extravasation (renal pelvis or ureteropelvic junction injury)
  4. Hematoma > 3.5cm
  5. Lack of contrast enhancement of the parenchyma (main renal arterial injury)
  6. Active intravascular contrast extravasation (arterial injury with brisk bleeding)

CT scan showing left renal artery injury (source: Wikipedia)

• Differential diagnosis of fluid collections seen on serial imaging for renal trauma (3):

1. Hematomas - density is almost always > 30 HU
2. Urinomas - density ranges from 0-20 Hounsfield units (HU)
3. Abscesses -associated with rim enhancement; perinephric abscess rarely occurs after renal injury

AAST Grading

(Table to be created)

*Advance one grade for bilateral injury up to grade III

What Grade of injury is this based on the AAST classificaton?

Source: Wikipedia

Management

• Management of traumatic renal injuries has shifted from operative exploration to non-operative management in the vast majority of cases.
  • Non-operative management of the vast majority of blunt renal injuries is firmly established; non-operative management of penetrating and high-grade renal injuries remains debatable
• Indications for intervention
  • AUA: based on hemodynamic stability
    • If hemodynamically stable: non-invasive management
      • Non-invasive management includes close hemodynamic monitoring, bed rest, ICU admission, and blood transfusion (when indicated)
      • Patients initially managed noninvasively may still require surgical, endoscopic, or angiographic treatments at a later time, especially those with higher grade injuries.
      • Factors associated with increased risk of bleeding and need for intervention in grade 3 and 4 injuries:
        1. Medial hematoma
        2. Hematoma > 3.5-4 cm in thickness
        3. Presence of a contrast extravasation from vessels on imaging
      • Although devitalized parenchyma has been suggested as a risk factor for development of septic complications, evidence supporting intervention for this radiographic finding is inconclusive
      • All patients with high-grade injuries selected for nonoperative management should be closely observed with serial hematocrit readings and vital signs (Campbell’s)
        • Some empirically prescribe bed rest until gross hematuria resolves, though insufficient evidence to support its efficacy
    • If hemodynamically unstable: immediate intervention (surgery or selective angioembolization)
      • For hemodynamically unstable patients with radiographic findings of large perirenal hematoma (> 4 cm) and/or vascular contrast extravasation in the setting of deep or complex renal laceration (AAST Grade 3-5), surgeons should perform immediate intervention
        • Perinephric hematoma size provides a rough radiographic estimate of the magnitude of renal bleeding, and increasing hematoma size has been incrementally associated with higher intervention rates.
      • Selected patients with bleeding from segmental renal vessels may benefit from angioembolization as an effective yet minimally invasive treatment to control bleeding
        • Selective embolization provides an effective and minimally invasive means to stop active bleeding from parenchymal lacerations and segmental arterial injury
        • Increasingly used in renal trauma
      • Patients who are hemodynamically unstable despite active resuscitation should be taken to the operating room rather than angiography
  • Campbell’s 11th edition
    • Indications for operative management
      • Absolute (4) 5PUPS:
        • Suspected grade 5 injury (renal vascular pedicle avulsion)
        • Expanding/Pulsatile renal hematoma (usually indicating renal artery laceration)
        • Some blunt and penetrating abdominal trauma may require laparotomy because of associated non-urologic injury, but even in these cases it is not necessary to explore the kidney additionally. However, exploration is needed in the case of a pulsatile and expanding retroperitoneal hematoma that suggests renal artery laceration
        • UreteroPelvic junction disruption
        • Hemodynamic instability with Shock
      • Relative indications (3):
        • Renal injury together with colon/pancreatic injury
        • Urinary extravasation with significant renal parenchymal devascularization
        • Delayed diagnosis of arterial injury
• Surgical management
  • Nephrectomy is a frequent result when hemodynamically unstable patients undergo surgical exploration
  • Approach: transabdominal
    • Allows complete inspection of intra-abdominal organs and bowel.
  • Principles of renal reconstruction after trauma include (8):
    1. Complete renal exposure
    2. Measures for temporary vascular control
       1. Isolate the renal vessels before exploration to provide the immediate capability to occlude them if massive bleeding should ensue when the Gerota fascia is opened
    3. Limited debridement of nonviable tissue
    4. Hemostasis by individual suture ligation of bleeding vessels
    5. Watertight closure of the collecting system if necessary/possible
    6. Reapproximation of the parenchymal defect
    7. Coverage with nearby fascioadipose flaps (Gerota fascia or omentum) if feasible
       1. The open parenchyma should be covered when possible by a pedicle flap of omentum. The rich vascular and lymphatic supply of the omentum promotes wound healing and decreases the risk for delayed bleeding and urinary extravasation.
    8. Liberal use of drains
  • For major renovascular injuries in patients with 2 kidneys, speedy nephrectomy is advocated
    • In rare instances in which vascular repair is technically feasible, renal salvage rates are disappointingly low
  • In damage control surgery, the area around the injured kidney is packed with laparotomy pads to control bleeding, with a planned return in approximately 24 hours to explore and evaluate the extent of injury.
    • This allows the cold, acidotic, and coagulopathic patient to be stabilized in the ICU before any attempt at potentially lengthy renal reconstruction is attempted.
  • In an unstable patient, if damage control is not an option, total nephrectomy would be indicated immediately when the patient’s life would be threatened by attempted renal repair.
  • Delayed renal bleeding can occur up to several weeks after injury but usually occurs within 21 days.
• Renal injury with urinary extravasation
  • Stable patients where renal pelvis or proximal ureteral injury is not suspected: observation (AUA)
    • Parenchymal collecting system injuries often resolve spontaneously.
      • Urinary extravasation alone from a grade IV parenchymal laceration or forniceal rupture managed non-operatively has a spontaneous resolution of > 90%
  • Indications for intervention (4):
    1. Suspected injury to renal pelvis or proximal ureteral avulsion
       1. Suggested by large medial urinoma or contrast extravasation on delayed images without distal ureteral contrast)
       2. Management is either endoscopic or open depending on the clinical scenario
    2. Urinoma increasing in size, purulence, or complexity on follow-up imaging
    3. Presence of complications such as fever, infection, increasing pain, ileus, or fistula.
    4. Severe renal injuries with continued urinary extravasation (not described in 2020 AUA Guidelines)
       • Placement of an internal ureteral stent for drainage may prevent prolonged urinary extravasation and decrease the chance of perirenal urinoma formation
         • Persistent urinary extravasation can result in urinoma, perinephric infection, and, rarely, renal loss.
  • Options for intervention
    • Ureteral stent (preferred)
      • An internalized ureteral stent is minimally invasive and alone may provide adequate drainage of the injured kidney
      • A period of concomitant Foley catheter drainage may minimize pressure within the collecting system and enhance urinoma drainage
    • Percutaneous urinoma drain, percutaneous nephrostomy, or both may also be necessary
• Follow-up in patient's managed non-operatively
  • Indications for follow-up CT imaging (after 48 hours) in renal trauma patients (2): (AUA)
    1. Clinical signs of complications (e.g., fever, worsening flank pain, ongoing blood loss, abdominal distention)
    2. Deep lacerations (AAST Grade IV-V)
       • AAST Grade IV-V renal injuries are prone to developing troublesome complications such as urinoma or hemorrhage
       • AAST Grade I-III injuries have a low risk of complications and rarely require intervention. Routine follow-up CT imaging is not advised for uncomplicated AAST Grade I-III injuries because it is not likely to change clinical management in these cases
• Hypertension and Renal Trauma
  • Hypertension is rarely noted in the early postinjury period but can occur later.
    • Rare cases of acute renovascular hypertension have been described, and can be treated with antihypertensives, observation, or uncommonly, nephrectomy
    • Mechanisms for hypertension as a complication of renal trauma (4):
      1. Renal vascular injury, leading to stenosis or occlusion of the main renal artery or one of its branches (one-clip, Goldblatt kidney)
      2. Page kidney: compression of the renal parenchyma with extravasated blood or urine
      3. Post-trauma arteriovenous fistula
      4. Ureteral / UPJ obstruction§
         • In the first 3 scenarios, the renin-angiotensin axis is stimulated by partial renal ischemia, resulting in hypertension