From the Guidelines
To diagnose hepatic steatosis, imaging studies such as abdominal ultrasonography, computed tomography (CT), magnetic resonance imaging (MRI), and magnetic resonance spectroscopy (MRS) are recommended.
Diagnostic Methods
- Abdominal ultrasonography is commonly used to diagnose hepatic steatosis and has high accuracy for detecting moderate and severe steatosis, but it has suboptimal sensitivity for mild steatosis 1.
- CT scan can help visualize the liver and detect fat accumulation, and a liver-to-spleen attenuation ratio of less than 1 can be indicative of hepatic steatosis.
- MRI and MRS are reliable tools for assessing the amount of steatosis and can detect 5-10% of steatosis 1.
- Controlled attenuation parameter (CAP), a novel, inexpensive ultrasound-based elastography method, can also be used to measure hepatic steatosis 1.
Additional Diagnostic Tools
In some cases, a liver biopsy may be necessary to confirm the diagnosis and assess the extent of liver damage, as it is considered the most sensitive means of obtaining pertinent, comprehensive information from the liver 1.
Important Considerations
It is essential to rule out other liver diseases, such as hepatitis or cirrhosis, and to assess for potential complications of hepatic steatosis, such as fibrosis or steatohepatitis 1. A fasting lipid profile and glucose test should also be performed to evaluate for metabolic syndrome, which is often associated with hepatic steatosis 1. In terms of specific diagnostic criteria, a liver ultrasound showing a bright liver texture with increased echogenicity, or a CT scan showing a liver-to-spleen attenuation ratio of less than 1, can be indicative of hepatic steatosis 1. A liver biopsy showing more than 5% of hepatocytes containing fat droplets can confirm the diagnosis 1. It is crucial to note that hepatic steatosis can be asymptomatic, and diagnosis often occurs incidentally during evaluation for other conditions 1.
From the Research
Methods for Diagnosing Hepatic Steatosis
The diagnosis of hepatic steatosis can be achieved through various methods, including:
- Liver biopsy, which remains the gold standard for diagnosing and staging nonalcoholic fatty liver disease (NAFLD) 2
- Non-invasive imaging methods, such as:
- Ultrasonography (US), which is widely available and radiation-free, but may not be able to examine the entire liver 3
- Computed Tomography (CT), which is readily available and helpful for detection and risk classification, but exposes users to radiation 3
- Magnetic Resonance Imaging (MRI), which can measure liver fat percentage with magnetic resonance imaging proton density fat fraction (MRI-PDFF) and is considered the best imaging indicator for early liver fat detection 3
- Quantitative ultrasound-based imaging techniques, which have improved the ability to detect and quantify hepatic steatosis and possess many inherent advantages, including universal availability, real-time capability, and relatively low cost 4
- Other non-invasive diagnostic modalities, such as the controlled attenuation parameter using transient elastography and Xenon-133 scan, which have been proposed to increase the ability to diagnose NAFLD and avoid liver biopsy 2
- The hepatorenal index by B-mode ratio, which has been shown to diagnose steatosis with moderate accuracy in patients with alcohol-related or nonalcoholic fatty liver disease, comparable to B-mode ultrasound steatosis scoring and controlled attenuation parameter 5
Evaluation of Liver Biopsies
The evaluation of liver biopsies with steatosis requires a stepwise approach, including:
- Assessment of the degree of steatosis
- Presence or absence of ballooning degeneration
- Lobular inflammation
- Fibrosis 6 Effective evaluation of liver biopsies with steatosis also requires careful histologic examination and correlation with clinical history, particularly regarding medications, nutrition status, and alcohol use 6