Thoracic Infection Flashcards
Broad pathologies of the lung
In broad terms pathologies of the lung can be divided into two main categories:
Airspace
Interstitial
Locational features which may aid the diagnosis of lung infections
Community acquired infections tend to cause diffuse filling of airspaces and as such result in lobar consolidation. Nodular pattern is more commonly seen in TB. Peri-hilar distribution is seen in opportunistic infection.
Features of Opacification vs Consolidation
Consolidation: Can see Air Bronchograms
Opacifications: Cannot
Features of PCP on CXR
PCP
PCP is a disease which involves the interstitium and airspace and is often complicated by lung cysts. As a consequence, PCP has many patterns of abnormality on the CXR which reflects these changes.
In this case there are various patterns of abnormality. Rings are likely to be due to lung cysts, lines indicate involvement of the interstitium and diffuse opacification(*) in the middle lobe indicates airspace disease.
Features of a loculated empyema
PA CXR demonstrates opacification in the mid right hemithorax. The hilum and vascular marking are clearly seen though this abnormality. This indicates that the abnormality lies outside the lung, probably within the pleura.
Features of Viral Pneumonia
There is reticular-nodular opacification in the peripheries of
both mid and lower zones, and a confluent area of opacification in the right mid zone.
The reticular-nodular pattern of abnormality is more typical of an interstitial rather than air space process. Viral pneumonia is one of the infections which can cause both an interstitial and air space disease pattern of abnormality.
Teaching Point
Distribution and cavitation
Upper lobe changes - think TB
Cavitation - think TB, staph aureus and gram negative infections
Cavitation and immunosuppressed - think aspergillus
Bilateral and perihilar - think PCP
Nodular - think TB
Features of aspergilloma on CXR and CT
In the left lung there is an ill defined mass containing a concentric lucency. Appearance is typical of an aspergilloma.
CT demonstrates multiple nodules with ill defined margins, air crescent formation
and a ground glass halo (*). The appearances are typical of an invasive aspergillosis infection.
Features of Bronchopneumonia
The pre-employment chest radiograph demonstrates
assymmetry at the apices, nodules throughout the left upper lobe and lingula and loss of clarity of left heart border. These appearances are consistent with a bronchopneumonia while the upper lobe distribution is typical of TB.
The follow-up demonstrates progression in the changes and cavitation at the apex, confirming bronchopneumonic TB.
Causes of air-space disease
Fluid - cardiogenic and non-cardiogenic pulmonary oedema, protein
Pus - pneumonia
Blood - vasculitis, infarction
Cells - malignant (lymphoma, alveolar cell carcinoma) and inflammatory (sarcoid, EAA, eosinophilia, radiation, BOOP)
Protein - alveolar proteinosis
Features of Miliary TB
This was a 50 year old male, UK born, Asian patient with a 6 month history of malaise and occasional cough. The patient was otherwise well.
The radiograph demonstrates subtle nodules scattered throughout the lungs particularly in the right mid zone. Similar changes were present on a chest radiograph 4 months previously.
The HRCT demonstrates widespread nodules with a random distribution throughout the lung. There is involvement of both the septae/fissures, pleura, bronchovascular bundles and centrilobular structures.
The diagnosis was milary tuberculosis, HIV positive.
The radiograph appearances are non specific. TB was initially considered, however this seemed unlikely in view of the static nature of the nodules. ‘Random distribution’ of nodules seen on the HRCT is typical of haematogenous spread of tuberculosis.
Milary tuberculosis can occasionally present with an indolent course, as in this case, and is a recognised feature of TB in patients who are HIV positive.
