• ARDS is a clinical syndrome with specific diagnostic criteria based on symptoms, imaging, and oxygen levels.
• DAD is a histological pattern of lung injury, most commonly seen in ARDS but not exclusively limited to it.
• ARDS is characterized by an
  • acute and diffuse inflammatory damage
  • into the alveolar-capillary barrier
    • increased vascular permeability
  • Caused by
    • • direct (pulmonary ARDS) or
      • indirect (nonpulmonary ARDS),
      • Most Common
  • Resulting in
    • early changes
      • diffuse bilateral coalescent opacities
      • caused by proteinaceous interstitial edema
      • (not reversible by treatment with diuretics)
    • after about a week
      • developing into alveolar edema due to pneumocyte type 1  damage and
      • resulting in hyaline membrane disease
• CT
  • Two basic forms
    • Direct pulmonary disease caused by pulmonary factors
      • more heterogeneous asymmetrical distribution
    • Indirect caused by a systemic ailment
    • results in a more diffuse homogeneous process with symmetrical distribution
  • Acute Phase
    

    Early phase

Anteroposterior density gradient

Ground Glass Opacities
Dense  consolidation in the most dependent regions, merging  Subpleural Sparing
Normal or hyperexpanded lung in the non-dependent regions

Memory Image

• • Exudative (acute) phase: 1 – 7 days
    • 

      

      

      

      Radiology and Pathology

Neutrophil mediated inflammation

• • • neutrophils predominate in the first 6 to 24 hours
      • (monocytes predominate in 24-48 hours)
    • Neutrophils destroys the alveolar capillary barrier (alveolar epithelium and endothelium),
    • increases its permeability
    • results in intra-alveolar hemorrhage and
    • edema
    •  interacts with alveolar surfactants,
    • resulting in decreased pulmonary compliance
    • hyaline membranes develop in the alveolar wall
• Proliferative / organizing (subacute) phase: 8-14 days
  • restoration of type II pneumocytes a
  • differentiation into type I pneumocytes
  • proliferation of myofibroblasts

  • Exudate

Exudate and Hyaline Membranes

Mucus Like Exudate creating a Shiny Surface

Myofibroblast Proliferation

53 F ARDS Acute Exudative Phase
Ground Glass Pattern Basilar Consolidation (A-P gradient) and Subpleural Sparing

 Chronic Fibrotic Phase

• Fibrotic (chronic) phase: after 3 weeks
  • Collagenous fibrosis in
    • alveolar spaces and
    • interstitium
  • rigidity of alveoli due to architectural remodeling

• • 

    

8 Months Later – Diffuse Ground Glass Pattern with Mild Traction Bronchiectasis

 

Post MVA 58M Acute Exudative Phase

Post MVA 12 Days Later – Improving  Non Cardiogenic Edema and Third Spacing 

 

ARDS – Dominant Central Distribution with Relative Lower Lobe Subpleural Sparing

79 Year Old Male 2 Weeks Earlier in CHF

Patient Developed Sepsis and 2 Weeks Later Radiological Features of ARDS 

Diffuse Ground Glass Changes Subpleural Sparing

 

54 Year Old Female with sepsis,  ARDS and
A-P Density Gradient

Ground Glass Pattern with Patchy Infiltrates and A-P Gradient

MVA ARDS Bibasilar Consolidation and A-P Density Gradient

 

 

 

 

AIP ARDS Immunotherapy Toxicity

 

Diffuse Ground Glass ARDS vs Atypical Pneumonia

 

 

70F Aspiration and Pneumonia with Crazy paving

 

62F-ARDS-post-abdominal-surgery-and-abdominal -abscess-shock

 

Ground-glass Opacification Consolidation and Subpleural Sparing
Secondary to Trauma

Sickle Cell Crisis, Acute Chest Syndrome , ARDS

Patient with HIV Fournier Gangrene ARDS with GGO and focal Consolidations Symmetrical Involvement

• While ARDS is a clinical syndrome with specific diagnostic criteria based on symptoms, imaging, and oxygen levels.
• DAD is a histological pattern of lung injury, most commonly seen in ARDS but not exclusively limited to it.
  • Diffuse alveolar damage (DAD) is manifested by
    • injury to alveolar lining and
    • endothelial cells,
    • pulmonary edema,
    • hyaline membrane formation and
      • later by proliferative changes involving
        • alveolar and
        • bronchiolar lining cells and
        • interstitial cells
• DAD is the stereotypical morphology of ARDS,
• Clinical syndrome of ARDS is not synonymous with the pathologic diagnosis of DAD
• DAD pattern is often characterized by hyaline membranes in acute phase but shows a wide variety of findings that makes the diagnosis challenging
• Buzz in a Nutshell
  • Acute
  • Diffuse
  • Extensive
  • bilateral
  • without upper or lower lobe predominance
  • Can be regional,
    • depending on the degree and cause of the inflammation
• Alveoli
• Causes either
• pulmonary or
• severe systemic disease

References and Links

Radiopaedia

• Akira Yoshikawa, M.D., Andrey Bychkov, M.D., Ph.D. Pathology Outlines  ARDS / DAD
• Sheard S et al Imaging of Acute Respiratory Distress Syndrome Respiratory Care April 2012, 57 (4) 607-612

 

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