Most other toxins result in ↓ density due to steatohepatitis ± hepatocellular necrosis
• May show other inflammatory changes, such as periportal or gallbladder wall edema
• Volume loss of liver and ascites are bad prognostic signs
TOP DIFFERENTIAL DIAGNOSES
• Hepatitis (alcoholic, viral, autoimmune)
Imaging cannot distinguish among causes of acute hepatitis
• Steatosis (fatty liver)
PATHOLOGY
• Acetaminophen (paracetamol or Tylenol)
Most common cause of severe toxic injury in USA and Europe (40-50% of cases)
CLINICAL ISSUES
• Acute abdominal pain, nausea, vomiting
• May quickly progress to complete hepatic failure
• Usually leads to complete recovery or liver failure within 72 hours
Acute liver failure must be treated with liver transplantation to avoid fatal outcome
DIAGNOSTIC CHECKLIST
• Global or focal liver volume loss ± ascites = bad prognosis
(Left) Axial NECT of a 41-year-old woman who developed acute liver failure after taking an excessive dose of acetaminophen shows diffuse low attenuation throughout the liver, which is due to acute massive hepatocellular necrosis rather than steatosis, although the imaging features are indistinguishable.
(Right) Axial CECT section of the same patient shows only diffuse hypoattenuation throughout the liver and ascites on lower sections. The patient developed hepatic failure within 24 hours of this scan.
(Left) The same patient required urgent liver transplantation. The explanted liver shows signs of massive hepatocellular necrosis and acute inflammation.
(Right) H&E of acute liver failure shows confluent necrosis with lymphoplasmacytic inflammation (left). Swelling and inflammation are seen in the remaining parenchyma (right). (Courtesy S. Kakar, MD.)
TERMINOLOGY
Definitions
• Injury to liver induced by exogenous toxins, either through direct hepatotoxicity or idiosyncratic reaction
IMAGING
General Features
• Best diagnostic clue
Imaging may be normal or show diffuse ↑ or ↓ density
– May show other inflammatory changes, such as periportal or gallbladder wall edema
– Amiodarone results in increased density; most other toxins result in ↓ density due to steatohepatitis ± hepatocellular necrosis
CT Findings
• Hepatomegaly
• Diffuse or multifocal hypodensity in liver
May represent steatosis, steatohepatitis, &/or hepatocellular necrosis
• Volume loss of liver (global or lobar)
Bad prognostic sign
Often indicates massive hepatocellular necrosis
• Ascites (bad prognostic sign)
MR Findings
• Steatosis in some cases
Signal loss on opposed-phase T1W GRE MR
Ultrasonographic Findings
• Hepatomegaly
• ↑ or ↓ echogenicity of liver
Steatosis vs. hepatic “edema” from acute injury
• Periportal edema ± gallbladder wall edema
Imaging Recommendations
• Best imaging tool
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