Subcapsular Hematoma and Renal Laceration

General considerations

• Incidence
• Renal trauma is most common of all GU trauma occurring in about 10% of patients with significant blunt or penetrating abdominal trauma
• Cause
• Motor vehicle accident
• Contact sports
• Falls and fights
• Less often penetrating wounds
• Mechanism
• Direct blow (>80%) frequently compressed and often lacerated by lower ribs
• Acceleration-deceleration injuries can produce renal artery tears
• Associated with other organ injury in 20% of cases
  

Clinical findings

• More than 95%  have hematuria
• About 25% of patients with gross hematuria have significant injuries
• But, 24% of patients with renal pedicle injury have no hematuria
• Only 1-2% with microhematuria have a severe renal injury

Types of injuries

• Renal contusion
• Superficial cortical laceration (75-85%)
• Small cortical laceration without calyceal disruption
• Complete cortical laceration
• Fracture communicating with calyceal system (10%)
• Extraluminal contrast material
• Separation of renal poles or fracture
• Crush injury
• Usually involves injury to the renal vascular pedicle (5%)
• Multiple separate renal fragments
• Lack of enhancement of part or all of kidney
• Extraluminal contrast material
• Subcapsular hematoma

Imaging Findings

• Contrast-enhanced CT of the abdomen and pelvis is the study of choice
• Delayed scans may be needed to detect extraluminal contrast
• Contusion
• Focal patchy areas of decreased enhancement
• Renal laceration
• Irregular linear hypodense parenchymal areas
• They may be hyperdense if they contain blood
• Fracture
• Laceration connecting two cortical surfaces
• Shattered kidney
• Multiple separated renal fragments with or without perfusion
• Subcapsular hematoma
• Superficial crescentic, usually hyperdense zone beneath renal capsule and compressing adjacent parenchyma
• Less common than perinephric hematoma
• Perinephric hematomas presents as a poorly-defined, hyper-attenuating collection between Gerota’s fascia and the renal parenchyma
• They do not usually deform the shape of the renal parenchyma, even when large
• Subcapsular or perinephric hematoma is usually proportional to extent of injury
• Rarely, a subcapsular hematoma may compress the kidney sufficiently to produce renal perfusion and result in hypertension –the Page kidney
• Segmental arterial injury (infarction)
• Wedge-shaped perfusion defect, which persists even with delayed imaging
• Usually treated conservatively as they either resolve spontaneously or heal with small scar
• Devascularized kidney
• Diffuse non-perfusion of kidney
• Most often from a clot that forms in an incompletely torn renal artery
• Renal vein thrombosis
• Persistent nephrogram on delayed scans
• Active extravasation of contrast from renal artery
• Attenuation as bright as nearby arteries

Subcapsular hematoma and laceration of left kidney. This is a coronal reconstruction of a contrast-enhanced CT scan of the abdomen and pelvis. There is a subcapsular fluid collection that compresses the adjacent renal parenchyma (red arrow). In addition, there is a lucency traversing the lower pole of the kidney that represents a renal laceration.
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eMedicine Smith, J; Schauberger, J; Kenny, P; Cheer, A; and Lobera, A