What CT imaging findings may be encountered in hepatic trauma?
The liver is the most commonly injured solid organ in penetrating trauma, and the second most commonly injured solid organ in blunt trauma (following the spleen). The right hepatic lobe is more commonly involved by traumatic injury than the left hepatic lobe. CT is the mainstay of imaging evaluation of patients for potential hepatic trauma. Currently, the most widely used CT grading system for hepatic injury is based on the American Association for the Surgery of Trauma (AAST) scale. The spectrum of hepatic injuries includes contusion, hematoma, laceration, avulsion, infarction, active hemorrhage, and vascular injuries including hepatic arterial pseudoaneurysm and juxtahepatic (hepatic vein, portal vein, or inferior vena cava) venous injuries. Patients with higher grade injuries (IV to VI) are more likely to be unstable and in need of surgical or percutaneous vascular intervention.
Hepatic hematomas appear as foci of nonenhancing high attenuation (30 to 70 HU) hemorrhagic fluid on CT, either subcapsular or intraparenchymal in location. When active hemorrhage is present, one sees focal areas of increased attenuation on contrast-enhanced images similar to that of enhancing vessels that do not conform to known vascular structures and that persist or increase in size on more delayed phase acquisitions. Hepatic arterial pseudoaneurysms also appear as well-circumscribed foci of contrast enhancement with attenuation similar to adjacent contrast-enhanced arteries but decrease in attenuation on more delayed phase acquisitions.
Hepatic contusions appear as focal or more diffuse areas of hypoattenuation within the liver, although they may sometimes be isoattenuating relative to surrounding liver parenchyma or hyperattenuating when there is associated hemorrhage.
Hepatic lacerations appear as linear, irregular, or branching nonenhancing low attenuation parenchymal defects in the liver, often paralleling intrahepatic venous structures, and often with adjacent areas of high attenuation hemorrhage. When severe, portions of hepatic parenchyma may even avulse from the remainder of the liver.
Hepatic infarcts appear as peripheral, often wedge-shaped, areas of nonenhancement in the hepatic parenchyma.