Radiology of pulmonary infections

taken from the book by dr sumer k sethi review of radiology

PULMONARY INFECTIONS

Radiology of Pulmonary Tuberculosis:
Primary TB:
• Ghon’s lesion: Subpleural consolidation + lymphatic + enlarged lymph nodes
• Lymphadenopathy is characteristic of primary infection ( also in Tuberculosis with AIDS)
• Consolidation can occur anywhere in the lung. (More common subpleural sites in lower lobe)
Secondary TB
• Cavitation
• Fibrosis
• Involves Apical segments of upper and lower lobes
• V. UN COMMON IN ANTERIOR SEGMENT OF UPPER LOBE**
Hematogenous spread of TB leads to miliary shadowing
Endobronchial spread : Tree in bud appearance**
Rasmussen aneurysm: Pulmonary artery in cavity TB may cause hemoptysis**
—In hemoptysis—First vessel to be studied-Bronchial artery.

PNEUMONIA
Pneumococcal- more commonly basal, klebsiella more common right upper lobe, bulging fissure, mycoplasma earliest CXR change is fine reticulo-nodular shadows followed by consolidation. Viral pneumonias may show-peribronchial shadowing, reticulonodular shadows and consolidation
Bulging Fissure
• Klebsiella pneumonia (Freidlander’s bacillus)
• Lung abscess
• Ca bronchus
Hydatid Lung
• No or rare calcification in lung
• ‘Water lily’ sign OR CAMALOTE SIGN**
Hydatid cyst forms three layers:
Pericyst due to fibrous host reaction, ectocyst and the endocyst containing brood capsules.

ASPERGILLOSIS IN LUNG

1) ASPERGILLOMA
CXR show density surrounded by air in the cavity (air crescent sign)
Also seen in –
AIR Crescent sign
• Aspergilloma or fungal ball
• Inspissated pus in a cavity
• Tumour or clot within the cavity
• Hydatid cyst.

2) Invasive aspergillosis
In immunocompromised persons
CT Halo appearance due to surrounding haemorrhagic inflammation.

3) Allergic bronchopulmonary aspergillosis type III immune reaction, central bronchiectasis, ‘gloved finger appearance’

Pneumocystitis Carnii
CXR normal in 10% may show perihilar and mid/lower zone ground glass infiltrates, lymphadenopathy pleural effusion less common. Pneumothorax is well recognized complication.

Bronciectasis
Morphological Types(increasing severity)
1. Cylindrical
2. Varicose
3. Cystic
Radiological Signs **
· ‘Signet-ring’ sign- bronchus is larger than the accompanying vessel
· Tram track sign- Lack of peripheral tapering (cylindrical bronchiectasis)
· String of beads appearance alternate dilatation and constriction (varicoid bronchiectasis)
· Cluster of grapes appearance (cystic bronchiectasis)
Ø Investigation of choice: HRCT**
Ø Central Bronchiectasis is a Sign of Allergic Bronchopulmonary Aspergillosis (ABPA) **
Ø Idiopathic disease showing tracheobronchomegaly is mounier-kuhn syndrome.