Abdominal ultrasound

The Role of Ultrasound in Non-Alcoholic Fatty Liver Disease (NAFLD)

Comprehensive abdominal ultrasound is strongly recommended for all patients without exception suspected of having non-alcoholic fatty liver disease (NAFLD). In clinical practice, ultrasound—rather than elastography, computed tomography (CT), or magnetic resonance imaging (MRI)—is recognized as the optimal first-line tool for detecting this condition.

This recommendation has a high level of certainty (B) and is based on a level of evidence of 2.

Objectives of the Examination in NAFLD

During the procedure, the sonographer addresses three key tasks:

1. Determining liver dimensions. This allows the detection of hepatomegaly, which frequently accompanies fatty infiltration.
2. Assessing ultrasound characteristics of the parenchyma. Tissue homogeneity, presence of inclusions, and acoustic transmission are analyzed.
3. Determining liver echogenicity. This is the most important, key parameter for the instrumental diagnosis of steatosis. Increased echogenicity ("bright liver") is a direct indication of lipid accumulation in hepatocytes.

Diagnosis of Steatosis: Priority of Methods

In instrumental diagnostic algorithms for steatosis, comprehensive abdominal ultrasound firmly holds the position of the first-line method.

It is important to understand that at the initial stage of screening and confirmation, ultrasound surpasses other imaging modalities in terms of availability and informativeness. Despite the existence of high-tech methods such as contrast-enhanced abdominal CT, contrast-enhanced liver MRI, or elastography, standard grayscale ultrasound is ordered first for all patients with suspected steatosis within the context of NAFLD.

Ultrasound in Patients with Pulmonary Hypertension

The scope of comprehensive abdominal ultrasound is not limited to primary liver pathologies. This examination is strictly recommended for all patients with pulmonary hypertension (PH) (according to ESC guidelines: class IC, level of evidence 5, level of certainty C).

The main goal of the examination in this patient group is to reliably rule out concomitant liver pathology and/or portal hypertension. Clinical observations show that ultrasound provides invaluable assistance in diagnosing conditions associated with pulmonary arterial hypertension (PAH), specifically portal hypertension syndrome.

To improve diagnostic accuracy and quality in such patients, additional technologies are used during the ultrasound:

• The use of specialized contrast agents.
• The application of color Doppler flow mapping (CDFM) (which in this context is preferred over pulsed-wave spectral Doppler or power Doppler mapping).

Ultrasound Limitations and the Gold Standard for Portal Hypertension

Despite the high informativeness of ultrasound with CDFM in suspected portal hypertension, the method has its diagnostic limits. The clinician must keep a critically important rule in mind:

Reliable confirmation or complete exclusion of portal hypertension cannot be achieved solely based on the ultrasound picture. The definitive diagnosis is established only by performing transvenous cardiac catheterization (TVCC).

During this invasive procedure, pressure gradients are precisely measured. The diagnostic criterion is the difference between:

• Free hepatic venous pressure.
• Hepatic venous wedge pressure.

Thus, ultrasound acts as a powerful screening and primary assessment tool, but final verification of vascular gradients requires invasive intervention.

Class and exam questions

What else to study on this topic

• Criteria and grades of liver echogenicity changes in the development of steatosis.
• Physical principles of color Doppler flow mapping (CDFM) in the evaluation of portal system vessels.
• Technique and complications of transvenous cardiac catheterization (TVCC).
• Differential diagnosis of NAFLD and other diffuse liver diseases.

Prepared by WhiteCoat Pro faculty in accordance with the medical school curriculum. For educational purposes only.