Diagnostic Ultrasound - Abdomen and Pelvis

Acute Hepatitis
TERMINOLOGY
Definitions
• Inflammation of liver due to viral infection or toxic agents
IMAGING
General Features
• Best diagnostic clue
○ Acute viral hepatitis on US
– Hepatomegaly and diffusely hypoechoic parenchyma
– Steatohepatitis: Hepatomegaly and diffusely
echogenic liver parenchyma
• Location
○ Diffusely; involving both lobes
• Size
○ Acute: Enlarged liver
○ Chronic: Decrease in liver size
• Nonalcoholic fatty liver disease (NAFLD)
○ Hepatic steatosis: Abnormal and excessive accumulation
of lipids within hepatocytes
○ Important emerging cause of acute and progressive liver
disease
○ Estimated prevalence 30% in USA
• Alcoholic hepatitis
○ Acute: Hepatomegaly with echogenic liver
○ Chronic: Variable size of liver, echogenic liver
• Viral hepatitis
○ Infection of liver by small group of hepatotropic viruses
○ Stages: Acute, chronic active hepatitis and chronic
persistent hepatitis
○ Responsible for 60% of cases of fulminant hepatic failure
in USA
○ Leading cause of hepatitis
Ultrasonographic Findings
• Grayscale ultrasound
○ Acute viral hepatitis
– Hepatomegaly with diffusely hypoechoic parenchyma
– "Starry sky" appearance: Portal triads appear markedly
echogenic against background hypoechoic liver
(variably seen)
□ May be related to periportal edema
□ Periportal hypo-/anechoic area (hydropic swelling
of hepatocytes)
– Thickening of gallbladder (GB) wall; most common in
acute hepatitis A
○ Chronic active viral hepatitis
– Increased echogenicity of liver
– Loss of definition of portal vein walls
– Heterogeneous parenchymal echotexture due to
regenerating nodules
– Adenopathy in hepatoduodenal ligament
○ Acute alcoholic hepatitis
– Hepatomegaly with diffusely echogenic liver
parenchyma
– Increased hepatic artery diameter
□ Mean diameter in acute alcoholic hepatitis: 3.6 mm
vs. 2.7 mm in healthy patients
○ Late-stage alcoholic hepatitis
– Atrophic liver with micronodular cirrhosis
• Pulsed Doppler
○ Acute alcoholic hepatitis
– High-velocity hepatic artery
– Elevated hepatic artery peak systolic velocity (PSV) >
100 cm/s
□ Mean PSV: 187 cm/s vs. 66 cm/s in healthy patients
○ Acute or fulminant hepatotoxicity: May see markedly
elevated resistive indices of hepatic artery
CT Findings
• NECT
○ Acute viral hepatitis
– Hepatomegaly, GB wall thickening
○ Chronic active viral hepatitis
– Lymphadenopathy in porta hepatis/gastrohepatic
ligament and retroperitoneum (in 65% of cases)
– Hyperdense regenerating nodules
○ Acute alcoholic hepatitis
– Hepatomegaly
– Steatosis: Diffuse low-attenuation liver
□ Liver-spleen attenuation difference < 10 HU
□ Normal liver is 60-65 HU; < 45 HU is 100% specific
for steatosis
– Steatosis may be focal, lobar, or segmental
– Indistinguishable from nonalcoholic steatohepatitis
(NASH)
○ Chronic alcoholic hepatitis
– Mixture of steatosis and early cirrhotic changes
depending on chronicity
• CECT
○ Acute and chronic viral hepatitis
– ± heterogeneous parenchymal enhancement
○ Chronic hepatitis: Regenerating nodules may be
isodense with liver
MR Findings
• Viral hepatitis
○ Increase in T1 and T2 relaxation times of liver
○ T2WI: High signal intensity bands paralleling portal
vessels (periportal edema)
• Alcoholic steatohepatitis (fatty liver)
○ T1WI in-phase GRE: Increased signal intensity of liver;
greater than spleen or muscle
○ T1WI out-phase GRE: Decreased signal intensity of liver
(due to signal dropout from intravoxel lipid in liver)
– % fat = (T1IP-T1OOP)/(2*T1IP)
Imaging Recommendations
• Best imaging tool
○ Ultrasound to rule out biliary obstruction or other
hepatic pathology
DIFFERENTIAL DIAGNOSIS
Infiltrative Hepatocellular Carcinoma (HCC)
• Background cirrhosis
• Invasion of portal vein
Lymphoma
• Hepatomegaly due to diffuse infiltration
• Background vascular architecture may or may not be
distorted
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Diagnoses: Liver
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