Pneumonia

What's in the alveoli?

• Consolidation = Many bacteria + scattered polymorphs + oedema fluid.
  
  
• Red hepatisation = Packed with polymorphs + red cells + fibrin + fibrinous pleurisy.
  
  
• Grey hepatisation = Red cells lyse + fibrinous exudate persists.
  
  
• Resolution = Exudate resorbed/digested/expectorated + intact structure + pleura resolves or organises with adhesions.

This happens in both lobar and broncho pneumonia, but is more 'dramatic' in bronchopneumonia.

Pleural involvement is more common in lobar pneumonia, and complications are more common in lobar pneumonia.

Uncommon complications of pneumonia

1. Lung abscess (a localised suppurative area, characterised by necrosis).
2. Empyema.
3. Alveolar fibrosis in organisation.
4. Bacteraemia with metastatic abscesses --> endocarditis, meningitis, arthritis.
5. Pleural adhesions.
6. Bronchiectasis (caused by necrotising pneumonias, commonly due to anaerobes +/- aerobes and uncommonly due to S. aureus, Klebsiella, or S. pyogenes type 3 pneumococcus).
   

Lymphangitis carcinomatosis

What is lymphangitis carcinomatosis (LC)? Answer from emedicine.

The lungs are one of the most common targets for metastatic disease. Most pulmonary metastases are nodular, but a significant minority is interstitial. LC refers to the diffuse infiltration and obstruction of pulmonary parenchymal lymphatic channels by tumour.

Various neoplasms can cause lymphangitic carcinomatosis, but 80% are adenocarcinomas. The most common primary sites are the breasts, lungs, colon, and stomach. Other sources include the pancreas, thyroid, cervix, prostate, and larynx. LC can also arise from choriocarcinoma, melanoma, or metastatic adenocarcinoma from an unknown primary cancer.