Fatty Liver (Hepatic Steatosis): From Ultrasound Diagnosis to Quantification

Dr. Segnini
Dec 25, 2025
3 min read

Dr. Segnini Fatty liver ultrasound diagnosis

The Silent Liver Epidemic Fatty liver ultrasound diagnosis

Hepatic steatosis, commonly known as fatty liver , is the abnormal accumulation of triglycerides in liver cells (hepatocytes). It is the most common chronic liver disease worldwide , closely linked to metabolic syndrome, obesity, type 2 diabetes, and dyslipidemia . Its importance lies in the fact that, although it may initially be benign, it can progress to steatohepatitis (with inflammation), fibrosis, cirrhosis, and even liver cancer. Abdominal ultrasound is the first-line technique for screening and initial diagnosis due to its safety, accessibility, and low cost.

Why is ultrasound ideal for detecting fatty liver?

Ultrasound takes advantage of a fundamental principle: changes in the density of liver tissue due to fatty infiltration alter the way ultrasound waves pass through it and are reflected.

Non-invasive and safe: No radiation or need for contrast.
Widely available: It is part of any routine abdominal ultrasound.
High sensitivity: Detects steatosis when more than 20-30% of the liver is affected.
It provides additional structural information: It allows ruling out other causes of liver disease, such as masses, biliary obstruction, or cirrhosis.

Classic Ultrasound Findings: The "Bright" Liver

The diagnosis is based on the evaluation of echogenicity (the "degree of whiteness" in the image) and the attenuation of the ultrasound beam. The findings are always compared with the adjacent right kidney.

1. Main Sign: Increased Hepatic Echogenicity (Bright Liver )

Description: The liver parenchyma appears brighter ( hyperechoic ) than normal. In a healthy person, the liver is slightly more echogenic than the renal cortex, or isoechoic .
Key criterion: In steatosis, the liver becomes noticeably brighter than the cortex of the right kidney . This difference is the most important visual sign.

2. Ultrasound Beam Attenuation (Loss of Visualization of Deep Structures)

Description: Because fat "absorbs" and scatters more ultrasound, there is a progressive loss of beam penetration.
Manifestations:
- Diaphragm blurring : The hyperechoic , bright diaphragm line , normally clearly visible in the right and caudate hepatic lobes, becomes diffuse or disappears in deeper areas.
- Blurring of vascular borders: The walls of the intrahepatic veins and the portal vein, which are normally well defined, become unclear or imperceptible , especially in the deep parenchyma.
- General decrease in image definition in the posterior portions of the liver.

3. Other Associated Findings:

Heterogeneity: Fatty infiltration may not be uniform, leaving areas of normal parenchyma ( hypoechoic ) that resemble masses. These are called " spared liver areas" . areas ), typical around the gallbladder and portal fissure.
Hepatomegaly: The liver is usually enlarged.

Degrees of Steatosis on Ultrasound: A Semi-Quantitative Classification

Radiologists typically classify the severity of steatosis into three grades based on the above findings:

Grade 1 (Mild Steatosis): Slight increase in hepatic echogenicity . Vascular architecture and diaphragm are visualized normally . Subtle difference compared to the kidney.
Grade 2 (Moderate Steatosis): Marked increase in echogenicity . Loss of definition of the intrahepatic vessels and the posterior border of the diaphragm. Marked difference from the kidney.
Grade 3 (Severe Steatosis): Marked increase in echogenicity with complete loss of beam penetration . The diaphragm and deep vessels are not visible . The liver appears as a "white wall".

Beyond Conventional Ultrasound: Quantification Techniques

Conventional ultrasound is excellent for detection, but subjective for quantification. Today, advanced ultrasound techniques exist that measure fat objectively:

Attenuation Index Measurement: Some devices measure how much sound is attenuated as it passes through the liver. High attenuation indicates more fat.
Elastography ( FibroScan® with CAP): This is a revolutionary tool. The CAP device ( Controlled Attenuation Parameter specifically measures fat attenuation, providing a numerical value (in dB/m) that quantifies the percentage of steatosis more accurately and reproducibly. It is increasingly used for monitoring.

Differential Diagnosis: What Else Can Make the Liver Look Shiny?

Not all hyperechoic livers are fatty livers. It is important to consider:

Advanced Hepatic Fibrosis or Cirrhosis: Echogenicity may also increase , but it is usually accompanied by other signs (nodules, nodular surface, ascites).
Some medications.
Infiltrations by Other Materials (rareer). The clinical context (obesity, diabetes) is key to guiding the diagnosis.

Conclusion: The First Alarm and the Tracking Tool

Abdominal ultrasound plays a crucial dual role in the management of fatty liver. First, it acts as a silent alarm , detecting this condition early and non-invasively in patients who often have no symptoms. Second, it allows for follow-up to assess progression or, more importantly, regression. Steatosis can be managed with lifestyle changes (diet and exercise). While liver biopsy remains the gold standard, ultrasound, and especially techniques like CAP elastography , have democratized the diagnosis and monitoring of this global epidemic, effectively guiding clinical decisions.