TCV Definition: Lung Architectural Distortion

Etymology

• The term “architectural distortion” originates from the Latin word architectura, meaning “construction,” and reflects the disruption of normal lung structure.

AKA

• None.

Definition

What is it?

• Architectural distortion refers to the abnormal displacement or distortion of normal lung structures, including bronchi, vessels, fissures, or pleura, typically caused by scarring or external pressure.

Caused by:

• Fibrosis: Interstitial lung diseases such as usual interstitial pneumonia (UIP) or non-specific interstitial pneumonia (NSIP).
• Trauma: Lung contusion, surgery, or radiation therapy.
• Infections: Chronic or unresolved infections, such as tuberculosis or fungal infections.
• Neoplasms: Tumors causing distortion through mass effect or fibrosis (e.g., post-treatment scarring).
• Inflammatory Conditions: Sarcoidosis, organizing pneumonia.

Resulting in:

• Abnormal alignment or retraction of anatomical landmarks, such as fissures, vessels, or the bronchi.
• Functional impairments, including ventilation and perfusion mismatches.

Structural Changes:

• Retraction of pleural surfaces.
• Displacement of bronchi and vessels.
• Thickened interlobular septa and irregular fissures.

Pathophysiology:

• The distortion results from a combination of parenchymal injury, repair mechanisms (fibrosis or scarring), and mechanical traction exerted by the surrounding tissue.
• Chronic inflammation or fibroproliferative processes can stiffen and contract the lung parenchyma, leading to abnormal positioning of nearby structures.

Pathology:

• Dense collagen deposition in the interstitial spaces.
• Inflammatory cell infiltration or chronic granulomatous inflammation.
• Thickened alveolar septa and remodeled lung tissue.

Diagnosis

Clinical:

• Symptoms depend on the underlying cause and severity:
  • Progressive dyspnea in fibrotic lung diseases.
  • Chronic cough or chest discomfort.

Radiology:

• CXR:
  • Abnormal displacement of fissures, bronchi, or vessels.
  • Retraction or deformity of the lung contour.
• CT:
  • Precise evaluation of distorted anatomy with associated findings such as honeycombing, traction bronchiectasis, or fibrotic bands.

Labs:

• Supportive tests may include autoimmune markers for fibrotic diseases or microbiological studies for infections.

Treatment

• Directed at the underlying cause:
  • Antifibrotic therapies for UIP or NSIP (e.g., pirfenidone, nintedanib).
  • Corticosteroids for inflammatory diseases.
  • Antibiotics or antifungals for infections.
  • Surgical resection for localized neoplasms.

Radiology in Detail

CXR

Findings:

• Displacement or distortion of fissures, bronchi, or vessels.
• Volume loss in fibrotic regions.

Associated Findings:

• Reticulonodular patterns, opacities, or pleural thickening.

CT

Parts:

• Bronchi, blood vessels, interlobular septa, pleura, and fissures.

Size:

• Varies with the extent of distortion and underlying pathology.

Shape:

• Irregular or retracted lung margins and fissures.

Position:

• Abnormal positioning of lung structures, including displacement of hila or retraction toward fibrotic areas.

Character:

• Associated with traction bronchiectasis, pleural thickening, or honeycombing.

Time:

• Develops progressively in chronic fibrotic conditions.
• May stabilize or worsen depending on the disease course or treatment efficacy.

Associated Findings:

• Honeycombing in UIP, subpleural sparing in NSIP, or necrotic cavities in infections.

Other Imaging Modalities

MRI/PET CT/NM/US/Angio:

• MRI: Limited role but useful for assessing soft tissue and vascular involvement.
• PET-CT: Evaluates metabolic activity to differentiate active inflammation or infection from fibrosis.
• Ultrasound: May detect pleural involvement or associated effusions.

Key Points and Pearls

• Architectural distortion is a hallmark feature of fibrotic lung diseases and chronic structural lung damage.
• CT is the gold standard for identifying and characterizing architectural distortion and its associated findings.
• The recognition of distortion patterns, combined with clinical and laboratory findings, is essential for diagnosing underlying conditions such as UIP, NSIP, or chronic infections.
• Tracking the progression or stabilization of architectural distortion can guide treatment decisions and prognosis.