What is the management approach for fat stranding on a chest radiograph (CR)?

Management Approach for Fat Stranding on Chest Radiograph

When fat stranding is identified on chest radiograph, further evaluation with CT scan is strongly recommended as the next step in management to determine the underlying cause.

Understanding Fat Stranding

• Fat stranding appears as abnormally increased attenuation in fat tissue, often associated with regional free fluid or edema, representing inflammatory changes 1
• On chest radiographs, fat stranding may be subtle and difficult to characterize, making it a non-specific finding that requires further investigation 1
• This radiographic finding serves as an important clue to identify underlying pathology and should not be dismissed as incidental 1

Initial Assessment

• When fat stranding is identified on chest radiograph, assess for associated findings:

  • Pleural effusions or thickening 2
  • Parenchymal opacities or consolidation 2
  • Mediastinal widening or masses 2
  • Diaphragmatic abnormalities 2

• Consider clinical context alongside the radiographic finding:

  • History of trauma may suggest pneumothorax with associated fat pad displacement 3
  • Symptoms of acute pancreatitis with peripancreatic fat stranding extending to chest 2
  • Respiratory symptoms suggesting inflammatory or infectious process 2

Recommended Imaging Algorithm

Step 1: CT Chest

• CT chest is superior to chest radiography for characterization of fat stranding and identification of underlying pathology 2
• Contrast-enhanced CT is preferred as it provides better tissue characterization and detection of inflammatory changes 1
• CT can definitively localize lesions to specific compartments and demonstrate associated findings such as calcium, fluid, or masses 2

Step 2: Based on CT findings, consider:

• If mediastinal mass is identified:

  • MRI may be appropriate for further characterization of tissue planes and invasion 2
  • MRI is superior to CT for detection of invasion across tissue planes, including chest wall and diaphragm 2

• If inflammatory process is suspected:

  • Consider follow-up imaging in 6-12 weeks to ensure resolution 2
  • Use the same imaging modality (radiograph or CT) that initially detected the abnormality 2

• If cardiac etiology is suspected:

  • Consider cardiac-specific imaging such as cardiac CT or MRI 2
  • Echocardiography may be appropriate for evaluation of cardiac function 2

Specific Clinical Scenarios

Fat Stranding Associated with Pneumothorax

• The "floating cardiac fat pad sign" occurs when pleural air collects anteriorly and superiorly, lifting the pericardial fat pad off the diaphragm 3
• This finding should prompt further evaluation with chest CT or upright chest radiograph to confirm pneumothorax 3

Fat Stranding in Acute Pancreatitis

• Extensive peripancreatic fat stranding is a CT finding that correlates with severity in acute pancreatitis 2
• When seen extending into the chest, it indicates severe disease and may predict complications 2

Perivascular Epicardial Fat Stranding

• When identified on coronary CT angiography, perivascular fat stranding may indicate acute plaque rupture or spontaneous coronary artery dissection 4
• This finding is associated with a higher frequency of acute coronary syndrome (45.4% vs 3.8% in controls) 4

Pitfalls and Considerations

• Fat stranding is non-specific and can be associated with various conditions including:

  • Inflammatory processes 1, 5
  • Malignancy (more common with multiple areas of fat stranding) 5
  • Trauma (often affecting multiple areas) 5
  • Infection 2

• Differentiate true fat stranding from:

  • Normal anatomic variants of fat distribution 6
  • Extrapleural fat pads which may mimic pleural disease on plain radiographs 2
  • Fat thickening ("creeping fat"), which refers to increased volume of fat tissue rather than inflammatory changes 1

• MRI with fat suppression techniques can be valuable when CT findings are equivocal, as it can identify both macroscopic and microscopic fat 7