What are basilar reticulations on a chest X-ray (Chest X-ray)?

Basilar Reticulations on Chest X-ray

Basilar reticulations on chest X-ray are peripheral reticular opacities most profuse at the lung bases that represent a network-like pattern of fine lines, which are characteristic findings in patients with idiopathic pulmonary fibrosis (IPF) and other interstitial lung diseases. 1

Radiographic Appearance and Significance

Basilar reticulations appear as:

• Network-like linear opacities in the lower lung zones
• Usually bilateral, often asymmetric patterns
• Commonly associated with decreased lung volumes
• Most prominent in the peripheral/subpleural regions of the lungs 1

These findings are significant because:

• They may be visible on chest radiographs for several years before the development of symptoms 1
• They represent early interstitial changes that may indicate underlying fibrotic lung disease
• They are present in virtually all patients with IPF at the time of presentation 1

Differential Diagnosis

Basilar reticular patterns can be seen in multiple conditions:

• Idiopathic pulmonary fibrosis (IPF) - most common
• Asbestosis
• Connective tissue diseases (particularly scleroderma and rheumatoid arthritis) 1
• Fibrotic hypersensitivity pneumonitis
• Fibrotic nonspecific interstitial pneumonia (NSIP)
• Post-COVID-19 interstitial lung disease 2

Diagnostic Accuracy and Limitations

When a "confident" diagnosis of IPF is made based on chest radiograph showing basilar reticulations:

• It is correct in only 48-87% of cases 1
• A normal chest radiograph cannot exclude microscopic evidence of usual interstitial pneumonia (UIP) on lung biopsy
• High-resolution CT (HRCT) is significantly more accurate and should be performed when basilar reticulations are identified 1

Clinical Implications

The presence of basilar reticulations has important clinical implications:

• They may represent early fibrotic lung disease requiring further evaluation
• When identified incidentally (as interstitial lung abnormalities or ILAs), they are an independent risk factor for mortality 3
• The presence of reticulation is a risk factor for radiological progression of lung disease 3
• Nearly half of subpleural non-fibrotic ILAs with reticulations progress radiologically over 4 years 3

Recommended Next Steps

When basilar reticulations are identified on chest X-ray:

1. Obtain high-resolution CT (HRCT) scanning for detailed evaluation of the lung parenchyma
2. Consider detailed history of medication use and environmental exposures to identify potential causes of interstitial lung disease 1
3. Evaluate for signs and symptoms of connective tissue diseases
4. Consider pulmonary function testing to assess for restrictive defects
5. Multidisciplinary discussion may be needed to determine if lung biopsy is necessary 1, 4

Pitfalls to Avoid

• Mistaking basilar reticulations for normal lung markings
• Failing to obtain HRCT when basilar reticulations are identified
• Overlooking alternative diagnoses when reticulations are present
• Confusing reticulations with other patterns like ground-glass opacities 4
• Failing to recognize that basilar reticulations may represent early disease requiring follow-up 1

Basilar reticulations should prompt consideration of underlying interstitial lung disease, particularly IPF, and should not be dismissed as normal findings, especially in patients over 60 years of age.