Diagnostic Ultrasound - Abdomen and Pelvis

Hepatic Steatosis
Diagnoses: Liver
○ Metabolic derangement
– Poorly controlled DM (50%), obesity, hyperlipidemia
– Severe hepatitis and protein malnutrition
– Parenteral hyperalimentation, malabsorption
– Pregnancy, trauma, inflammatory bowel disease
– Cystic fibrosis, Reye syndrome
○ Hepatotoxins:Alcohol (> 50%), carbon tetrachlorides,
phosphorus
○ Drugs
– Tetracycline, amiodarone, corticosteroids
– Salicylates, tamoxifen, calcium channel blockers
• Associated abnormalities
○ NASH
– Subset of nonalcoholic fatty liver disease: Strong
association with metabolic syndrome
– Seen in patients with hyperlipidemia and diabetes
– May lead to "cryptogenic" cirrhosis
• Fat deposition in liver due to
○ Ethanol: Increased hepatic synthesis of fatty acids
○ Carbon tetrachloride/high-dose tetracycline: Decreases
hepatic oxidation/utilization of fatty acids
○ Starvation, steroids, and alcohol
– Excessively mobilizes fatty acids from adipose tissue
○ Segmental fatty infiltration: Where glycogen is depleted
from liver
– Decreased nutrients and insulin → decreased
glycogen
– Due to underlying mass, Budd-Chiari syndrome, or
tumor thrombus
○ Focal steatosis or sparing: Due to variations in hepatic
venous drainage
Staging, Grading, & Classification
• Sonographic grading for diffuse steatosis
○ Mild: Minimally increased parenchymal echogenicity and
normal-appearing intrahepatic vessel walls
○ Moderate: Further increased parenchymal echogenicity
causing decreased resolution of intrahepatic vessel walls
○ Severe: Markedly increased parenchymal echogenicity
causing inability to resolve intrahepatic vessel walls
• Nonalcoholic fatty liver disease (NAFLD)
○ Includes nonalcoholic fatty liver (NAFL) and NASH
○ May progress to cirrhosis and hepatocellular carcinoma
○ Risk factors: Obesity, sedentary lifestyle, diet, type II
diabetes, metabolic syndrome
Gross Pathologic & Surgical Features
• Enlarged, smooth capsule, rounded inferior contour
• Soft, yellow, greasy cut surface
Microscopic Features
• Triglyceride accumulation within hepatocyte cytoplasm
• Macrovesicular fatty liver (most common type)
○ Hepatocytes with large cytoplasmic fat vacuoles
displacing nucleus peripherally
○ Alcohol and diabetes mellitus
• Microvesicular
○ Fat is present in many small vacuoles
○ Reye syndrome
CLINICAL ISSUES
Presentation
• Most common signs/symptoms
○ Asymptomatic, but often with abnormal liver function
tests (LFTs)
○ Hepatomegaly in obese or diabetic patient
○ Alcoholics with acute injury: RUQ pain, tender
hepatomegaly
• Lab data
○ Asymptomatic: Normal/mildly elevated LFTs
○ Alcoholic and NASH: May have markedly abnormal LFTs
• Diagnosis:Biopsy and histology
○ Distinguish simple steatosis from steatohepatitis
○ Sampling error
○ MR Elastography: Emerging noninvasive means for
staging fibrosis and differentiating simple steatosis and
NASH
Demographics
• Epidemiology
○ Most common cause of chronic liver disease in Western
countries
○ 50% of patients with diabetes mellitus, > 50% of
alcoholics; 80-90% of obesity
○ Seen in 25% of nonalcoholics
○ Increasing in prevalence with epidemic of obesity and
metabolic syndrome
Natural History & Prognosis
• Alcoholics: Gradual disappearance of fat from liver after 4-8
weeks of adequate diet and abstinence from alcohol
• Resolves in 2 weeks after discontinuation of parenteral
hyperalimentation
• Steatohepatitis may progress to acute/chronic liver failure
• Steatosis is synergistic with viral hepatitis
Treatment
• Removal of alcohol or offending toxins
• Correction of metabolic disorders
• Lipotropic agents (like choline) when indicated
DIAGNOSTIC CHECKLIST
Consider
• Rule out other liver pathologies that may mimic focal or
diffuse steatosis
Image Interpretation Pearls
• Key on all imaging modalities is presence of normal vessels
coursing through fatty infiltration
SELECTED REFERENCES
1. Loomba R et al: Magnetic resonance elastography predicts advanced fibrosis
in patients with nonalcoholic fatty liver disease: a prospective study.
Hepatology. 60(6):1920-8, 2014
2. Borges VF et al: Sonographic hepatorenal ratio: a noninvasive method to
diagnose nonalcoholic steatosis. J Clin Ultrasound. 41(1):18-25, 2013
3. Kwon HJ et al: Value of the ultrasound attenuation index for noninvasive
quantitative estimation of hepatic steatosis. J Ultrasound Med. 32(2):229-35,
2013
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