Diseases characterised by Parenchymal opacification

Shivaprakash B HiremathDNB Resident

Normal lung density

•Slightly higher than air

Air in airspaces and small airways

Interstitial lung tissues

Wall of the alveoli

Small airways

Capillaries, blood in these

Vs

Increased lung opacity< in the amount of air

> size / volume of soft tissues

• Reduction in the volume (expansion) of the airspaces

• Partial or total replacement of the air in the airspaces by fluid or cells

• Increase in blood flow and blood volume in vessels

• Thickening of the interstitial tissues and of the alveolar wall

Degree of Opacification

•“Ground-glass opacity” - hazy increase in lung opacity that does not obscure the underlying vessels and bronchi

•“Lung consolidation” or “consolidation” - vessels and bronchial walls are obscured

•“Increased lung attenuation that have a density that is greater than soft tissue density”▫Development of calcifications within

existing lesions ▫Deposition of calcium within the lung

parenchyma ▫Diffuse or multifocal pulmonary ossification

Ground Glass Opacity

• Patchy distribution of ground-glass opacity Pneumocystis jiroveci pneumonia

Focal Vs Diffuse

Focal Vs Diffuse

Ground Glass Opacity

Diffuse ground-glass opacity Hypersensitivitypneumonitis

• Pulmonary haemorrhage in the right middle lobe

• Ill-defined GGO

• Sharply defined area of GGO in RUL• Pulmonary haemorrhage

GGO located near centre of the secondary pulmonarylobules and then look like ill-defined nodules

Reduction of Air in the Airspaces

•Volume Loss of the Alveoli▫Physiological phenomenon – development

of ground-glass opacity▫Increase in density in dependent lung

regions Lower lung > Middle and upper zones

Greater diaphragmatic movement Gravitational effectProne scans

Dependent density is no longer visible against the posterior chest wall and may appear against the anterior chest wall

•Volume Loss of the Alveoli▫Pathological changes in the lung and pleura

Fibrotic scarring in the lung Pleural thickening

Restrict lung expansion Ground-glass opacity

Decreased expansion right lung due to Right-sided malignant mesothelioma

•Replacement of Alveolar Air▫Partial filling of the alveolar spaces by fluid or

cells Alveolar proteinosis Respiratory bronchiolitis, bronchiolitis Interstitial lung disease Alveolar haemorrhage Bronchioloalveolar cell carcinoma

•Partial filling of the alveolar spaces + Thickening of the interstitium, alveolar walls = Crazy paving

Alveolar proteinosis• Areas of ground-glass opacity with intralobular reticular

pattern superimposed creating the crazy-paving pattern

• Increase in Parenchymal Perfusion▫> in capillary blood volume = > in lung

density▫Mosaic perfusion = Areas with >

attenuation (GGO) + < attenuation

Mosaic perfusionDecreased attenuation Increased lung attenuation

• Narrowing or obstruction of the blood vessels

• Small airways narrowing▫ Reflex vasoconstriction

• Redistribution of blood flow

GGO Vs Mosaic perfusionCalibre of the blood vesselsDelineation of the ground-glass opacityDensity changes after deep expiration

• Mosaic perfusion secondary to recurrent pulmonary embolism

Thickening of Parenchymal Interstitium / Alveolar Wall

•Minimal thickening of the alveolar wall, parenchymal interstitium = groundglass opacity

•Inflammation or infiltration•Intraalveolar cellular infiltrate, filling the

airspaces•Acute inflammation i.e indicating active

disease or reactivation of disease

•GGO ▫Fibrosis and result from fibrotic thickening

of the alveolar wall and interstitium•Be careful to diagnose GGO as an active

process▫Traction bronchiectasis or honeycombing

• Usual interstitial pneumonia in Systemic sclerosis• GGO in the dorsal and basal subpleural region of both

lungs, i.e active lung disease

•When a lung biopsy is performed, areas of ground-glass opacity are the best locations to be targeted, especially when no signs of fibrosis are present

• Diffuse ground-glass opacity in chronic hypersensitivity pneumonitis

• Bronchial deformation indicates pulmonary fibrosis

Acute Versus Subacute or Chronic Disease

Crazy-Paving Pattern

•Superposition of a linear pattern on ground-glass opacity = Crazy paving

•Pulmonary alveolar proteinosis

• Acute radiation pneumonitis in a patient treated for left-sided breast cancer

• Ground-glass opacity and consolidation

• Faint intralobular reticular pattern

• Crazy-paving pattern

Lung Consolidation

•Increase in lung density with obscuration of the underlying vessels & bronchial walls

•Bronchi can be recognised as an air bronchogram, i.e. low-density branching tubular structures

•Lung consolidation are similar to the lung changes that are responsible for ground-glass opacity

•Most frequent cause is a decrease in the amount of air in the airspaces

•Replacement of this air by fluid, cells, tissue or other substances

•Interstitial pneumonia (UIP)•Sarcoidosis

• Subpleural areas of lung consolidation• Eosinophilic pneumonia

Consolidation margins

•Consolidation has one or more sharply defined borders because the pathology reaches an anatomic structure such as a fissure

•Borders of consolidation that are not adjacent to the fissure may be,▫Sharply defined ▫Irregular and blurred▫Possibly surrounded with ground-glass

opacity

Sharp delineation by major fissure

• Lung consolidation and ground-glass opacity in a patient with overwhelming pneumonia

• Pulmonary infection with lung consolidation and GGO

•Airspace filling is the most frequent cause of consolidation, this pattern is often associated with,▫presence of centrilobular airspace nodules -

early airspace filling, ▫i.e bronchial distribution

Diseases producing ID-GGO:

•Diffuse pneumonias•Primarily opportunistic infections•Chronic interstitial diseases•Acute alveolar diseases•Unusual miscellaneous disorders

Increased Lung Attenuation more than Soft Tissue Density•Multifocal lung calcification•Granulomatous diseases

▫Tuberculosis▫Silicosis Associated with lung

nodules▫Sarcoidosis▫Amyloidosis

Metastatic calcification

•Deposition of calcium typically within the parenchymal, peribronchovascular interstitium▫Hypercalcaemia – abnormal calcium and

phosphate metabolism▫Chronic renal failure▫Secondary hyperparathyroidism

•Areas of GGO with calcification that may be inconspicuous or very dense or present as patchy areas of consolidation

•Consolidated lung parenchyma appears abnormally dense

• Metastatic calcification• Dense centrilobular ground-glass

opacities

• Metastatic calcification in consolidated lung in chronic renal failure and secondary hyperparathyroidism

Disseminated pulmonary ossification

•Small deposits of mature bone form within the lung parenchyma▫Chronic heart disease (mitral stenosis)▫Idiopathic pulmonary fibrosis (IPF)▫Asbestosis

Amiodarone lung toxicity

•Pulmonary toxic reaction with interstitial pneumonia and fibrosis

•Consolidated lung parenchyma may appear abnormally dense

•Liver and spleen appear abnormally dense as drug accumulates in the organs