Imaging Pearls ❯ Liver ❯ Fatty liver (steatosis)
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- “Hepatic steatosis can occur because of nonalcoholic fatty liver disease (NAFLD), alcoholism, chemotherapy, and metabolic, toxic, and infectious causes. Pediatric hepatic steatosis is also becoming more frequent and can have distinctive features. The most common pattern is diffuse form; however, it can present in heterogeneous, focal, multinodular, perilesional, perivascular, subcapsular, and lobar forms. Focal steatosis and fat sparing can occur because of the presence of veins of Sappey, pancreaticoduodenal vein, and aberrant right and left gastric veins, which drain into the liver as third inflow. Hypersteatosis and multinodular forms can mimic metastasis in patients with cancer.”
Hepatic Steatosis: Etiology, Patterns, and Quantification Idilman IS et al. Semin Ultrasound CT MRI 37:501-510 C 2016 - “Hepatic steatosis is defined as excessive triglyceride accumulation within the hepatocytes. There are 2 major conditions associated with hepatic steatosis: nonalcoholic fatty liver disease (NAFLD) and alcoholic fatty liver disease (AFLD). Besides, variable causes such as metabolic, nutritional, drug induced (chemotherapy and steroids), and hepatitis C virus (HCV) infection are listed in the pathogenesis of hepatic steatosis. The natural course of hepatic steatosis varies according to the etiology and accompanied conditions such
as inflammation and fibrosis, which has a potential to progress into cirrhosis and liver failure.”
Hepatic Steatosis: Etiology, Patterns, and Quantification Idilman IS et al. Semin Ultrasound CT MRI 37:501-510 C 2016 - “NAFLD is the most common form of hepatic steatosis and affects 30%-40% of men and 15%-20% of women in the general population.4 It is accepted as hepatic manifestation of metabolic syndrome and has a strong relationship with insulin
resistance, atherosclerosis, obesity, dyslipidemia, and hypertension. Accumulation of lipids in hepatocytes causes oxidative stress and inflammatory response that leads to nonalcoholic steatohepatitis (NASH), which may progress to cirrhosis. It is estimated that NAFLD would become the most common indication for liver transplantation by 2030.”
Hepatic Steatosis: Etiology, Patterns, and Quantification Idilman IS et al. Semin Ultrasound CT MRI 37:501-510 C 2016 - “Chronic alcohol intake is another cause of hepatic steatosis, and up to 90% of the alcoholic patients have AFLD. Patients with pure AFLD have a 10% risk of progressing to cirrhosis. Consumption of 30 g ethanol/day was shown to increase the risk of chronic liver damage and cirrhosis in alcoholic patients. Furthermore, female sex, cigarette smoking, obesity, and accompanying hepatic disorders are predisposing factors for liver damage in AFLD.” Hepatic Steatosis: Etiology, Patterns, and Quantification Idilman IS et al. Semin Ultrasound CT MRI 37:501-510 C 2016
- “Hepatic steatosis can be seen as an adverse reaction to some medications such as tetracycline, valproic acid, dexametha- sone, amiodarone, methotrexate, tamoxifen, and acetylsalicylic acid. Either microvesicular or macrovesicular steatosis can be observed in drug-induced hepatic steatosis (DIHS). The underlying metabolic syndrome and obesity may aggravate the process of DIHS. It generally occurs with therapy lasting several weeks or months and is reversible after discontinuation. However, some medications should be continued even after the detection of DIHS, such as chemotherapeutic agents, and it is important to monitor the signs of progressive liver damage, which can end up with portal hypertension in these patients.”
Hepatic Steatosis: Etiology, Patterns, and Quantification Idilman IS et al. Semin Ultrasound CT MRI 37:501-510 C 2016 - “Radiation-induced liver disease (radiation hepatitis) is a complication of radiotherapy and characterized with anicteric ascites, hepatomegaly, and elevated liver enzymes within 2-8 weeks after radiotherapy. Irradiated liver parenchyma can
appear hypodense at unenhanced CT scan and hypodense or hyperdense on enhanced CT scan. On MRI, it is detected as hypointense area on T1-weighted and hyperintense on T2-weighted images owing to edema. The borders of this area are straight with no anatomical congruity. Findings usually regress in 4-6 months, and irradiated area gradually shrinks with a compensatory hypertrophy in the remaining part of the liver .”
Hepatic Steatosis: Etiology, Patterns, and Quantification Idilman IS et al. Semin Ultrasound CT MRI 37:501-510 C 2016 - “Expected attenuation value of healthy liver is approximately and 8-10 HU higher than the attenuation of spleen. Park et al investigated diagnostic accuracy of hepatic attenuation value, liver-to-spleen attenuation ratio, and the difference of liver and spleen attenuation value for the diagnosis of macrovesicular steatosis of 30% or higher on unenhanced CT images; they observed the highest specificity (100%) for 42 HU, 0.8 and -9 HU, respectively, with no diagnostic superiority among them.”
Hepatic Steatosis: Etiology, Patterns, and Quantification Idilman IS et al. Semin Ultrasound CT MRI 37:501-510 C 2016 - “There are various etiologic causes and imaging patterns of hepatic steatosis, which are important for radiologic diagnosis. In patients with cancer, some forms of steatosis can mimic metastasis; therefore, in patients with equivocal findings on ultrasonography and CT, MRI should be performed for differential diagnosis. Quantification of hepatic steatosis beyond detection is feasible, and PDFF is becoming a biomarker for follow-up of patients with NAFLD. In the future, fatty acid maps may allow more detailed analysis of steatosis.”
Hepatic Steatosis: Etiology, Patterns, and Quantification Idilman IS et al. Semin Ultrasound CT MRI 37:501-510 C 2016
- Hepatic Steatosis
- Causes:
- Alcohol
- Drugs
- Obesity
- Pregnancy
- Diabetes
- Hyperlipidemia
- Chemotherapy (CASH) - Hepatic Steatosis
- Non-alcoholic fatty liver disease (NAFLD)
- Common cause of chronic liver disease
- Obesity is primary risk factor
- Up to 25% of adults
- 25% develop NASH (steatohepatitis)
- Inflammatory subtype of NAFLD
- Can progress to cirrhosis
- NASH and NAFLD cannot be distinguished on imaging - Hepatic Steatosis
- Imaging Findings:
- Non-contrast CT
- Density less than spleen = steatosis
- Liver attenuation - 40 HU
- Normally density is roughly 10 HU greater than spleen
- Non-contrast CT is the best CT method for detecting steatosis
- Contrast-enhanced CT:
- Never make diagnosis on arterial phase!
- 25 HU less than spleen on portal venous phase - Hepatic Steatosis
- Can be diffuse or focal
- Can be geographic
- Classic locations when focal:
- Falciform ligament
- Gallbladder fossa
- Along blood vessels and fissures
- No mass effect and vessels course undisturbed
- Focal fatty sparing
- Hepatic Steatosis
Causes:
- Alcohol
- Drugs
- Obesity
- Pregnancy
- Diabetes
- Hyperlipidemia
- Chemotherapy (CASH) - Hepatic Steatosis
Non-alcoholic fatty liver disease (NAFLD)
1. Common cause of chronic liver disease
2. Obesity is primary risk factor
3. Up to 25% of adults
4. 25% develop NASH (steatohepatitis)
- Inflammatory subtype of NAFLD
- Can progress to chronic liver disease & cirrhosis
- NASH and NAFLD are not distinguished on imaging - Hepatic Steatosis
Chemotherapy-related fatty liver (CASH)
- Common
- Caused by a number of different drugs
- Important to mention, as it can impact future treatment options - Hepatic Steatosis
Imaging Findings:
1. Non-contrast CT
- Density less than spleen = steatosis
- Liver attenuation less than or equal to 40 HU
- Normally density is roughly 10 HU greater than spleen
- Non-contrast CT is the best method for detecting steatosis
2. Contrast-enhanced CT:
- Never make diagnosis on arterial phase!
- 25 HU less than spleen on portal venous phase - Hepatic Steatosis
1. Can be diffuse or focal
2. Can be geographic
3. Classic locations when focal:
- Falciform ligament
- Gallbladder fossa
- Along blood vessels and fissures
- No mass effect and vessels course undisturbed
4. Focal fatty sparing - DDX Low Density Liver
1. Acute hepatitis
- Usually normal appearance on CT
- Perihepatic ascites and gallbladder wall edema
2. Fulminant Hepatic Failure
- Acetaminophen overdose
3. Disseminated Hepatic Infection
- Immunocompromised
4. Lymphoma (rarely diffuse mets or HCC)
5. Radiation-induced hepatitis - Radiation-Induced Steatosis
- Fatty Liver
- Often localized to the left lobe of the liver, but can vary depending on radiation field
- Cane be associated with enhancement in the acute setting