000 Subpleural Band Parenchymal Bands (Lungs)

Subpleural Band

Etymology

  • “Subpleural” originates from Latin: “sub-” meaning “beneath” and “pleura,” the membrane lining the lungs.

AKA

  • Subpleural Line, Parenchymal Band

What is it?

  • Subpleural bands are thin, linear opacities located adjacent to the pleural surface. These bands are typically associated with fibrosis and reflect structural changes in the subpleural regions of the lungs.

Characterized by

  • Thin, continuous lines parallel to the pleural surface.
  • Persistent and irreversible in fibrotic lung conditions.
  • Located within the intralobular interstitial tissue.

Anatomically affecting

  • Subpleural regions of the lung.
  • Intralobular interstitium, often interconnected with the visceral pleura and adjacent interlobular septa.

Causes include

  • Idiopathic: Idiopathic Pulmonary Fibrosis (IPF)
  • Inflammatory: Chronic Hypersensitivity Pneumonitis, Non-Specific Interstitial Pneumonia (NSIP)
  • Autoimmune: Systemic sclerosis, Rheumatoid lung disease
  • Occupational: Asbestosis, Silicosis
  • Iatrogenic: Post-radiation fibrosis

Histopathology

  • Dense collagen deposition within the intralobular interstitial tissue.
  • Chronic inflammatory cell infiltration.
  • Disrupted alveolar architecture leading to fibrosis.

Imaging Radiology

  • Applied Anatomy to CT
    • Parts: Intralobular interstitium and subpleural regions.
    • Size: Thin linear bands, typically 1-3 mm in width.
    • Shape: Continuous and parallel to the pleura, reflecting mechanical alignment with stress lines.
    • Position: Subpleural and lower lobes, often extending along the pleural surface.
    • Character: Persistent, non-resolving fibrosis associated with adjacent structural distortion.
    • Time: Chronic and stable, reflecting irreversible changes over time.
  • CXR: May appear as subtle peripheral linear opacities, difficult to distinguish without CT.
  • MRI: Rarely used but may show fibrotic regions as low signal intensity on T2-weighted images.
  • PET-CT: Typically no significant metabolic activity unless associated with inflammation or neoplasia.
  • Other: Ultrasound may reveal pleural thickening if present.

Differential Diagnosis

Differential Diagnosis

  • Subpleural Band:
    • Linear atelectasis
    • Pleural plaques
    • Peripheral interstitial fibrosis
  • Arcade-like Sign:
    • NSIP
    • Chronic Hypersensitivity Pneumonitis
    • Sarcoidosis
  • Linear Atelectasis:
    • Subpleural bands
    • Dependent pulmonary edema
Feature Subpleural Band Arcade-like Sign Linear Atelectasis
Definition Linear opacity parallel to the pleura Curvilinear opacity outlining lobules Thin linear opacity, gravity-dependent
Cause Chronic fibrosis Organizing pneumonia Dependent lung collapse
Histopathology Dense fibrosis in intralobular interstitium Fibroblast proliferation in perilobular tissue Compressed but reversible alveoli
HRCT Persistent thin lines; honeycombing may occur Perilobular curvilinear opacities; reversible Thin lines resolving with position change
CXR Subtle linear opacity in peripheral lung Patchy consolidation or curvilinear lines Faint linear opacity in dependent lung regions
Reversibility Irreversible Partially reversible with treatment Reversible with positional changes

 

Recommendations

  • Perform HRCT to characterize the extent and nature of subpleural bands.
  • Correlate imaging findings with clinical history and pulmonary function tests.
  • Consider biopsy if the underlying etiology is uncertain.
  • Prone imaging may help differentiate subpleural bands from linear atelectasis.

Key Points and Pearls

  • Subpleural bands are persistent features of fibrosis and are irreversible.
  • They align along anatomical planes and pleural surfaces due to mechanical forces.
  • Differentiation from other linear opacities, such as arcade-like signs or linear atelectasis, requires detailed imaging and clinical correlation.

Parallels with Human Endeavors

  • Examples in:
    • Social and Societal Equivalents: Subpleural bands represent the lasting scars of adversity, akin to enduring resilience in human experiences.
    • Art: The linear persistence of subpleural bands resembles minimalist art, with simple lines representing complexity beneath.
    • Sculpture: Structural reinforcements in sculptures mirror the stabilizing yet permanent effects of subpleural fibrosis.
    • Music: Linear patterns in fibrosis can be compared to recurring motifs in music, suggesting permanence and inevitability.
    • Dance: The flow and alignment of subpleural bands evoke graceful yet constrained movements.
    • Literature: These bands metaphorically echo the lasting imprints of life’s struggles on the human condition.
    • Quotes by famous people:
      • An arch consists of two weaknesses which, leaning one against the other, make a strength. Leonardo da Vinci
    • Poetry: “Waves etched by time, enduring the winds of change and gravity’s pull.”
    • Architecture:
      • Arches in Architecture
        • Ajuntament de Barcelona, saló de Cent
          This room, which was to serve for the meetings of the members of the Consell de Cent, was entrusted to the Master of Works Pere Llobet in 1369. A tombstone located at the bottom of the building informs that King Pere III celebrated the his first Consell dels Cent Jurats, on August 17, 1373. Initially, a rectangular room is designed, covered by a floor with two beams, divided by two stone arches. Courtesy Enric

          Ruins of the Burgondo chapel Treviño Country Spain
          Courtesy Basotxerri

Arches in Nature

      • Landscape Arch in the Devils Garden, the longest in the park and the fifth-longest in the world
        Work of Thomas Wolf
      • Subpleural bands reflect the physical stability influenced by forces such as gravity and lung motion, akin to the shaping of sea waves or the reinforcement of curved structures.