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Necrotizing Pneumonia (NP)

Necrotizing Pneumonia (NP)

  • Necrotizing pneumonia – rare and severe complication of bacterial CAP
    • Lies on a spectrum between lung abscess and pulmonary gangrene
    • Characterized by pulmonary inflammation with consolidation, peripheral necrosis + multiple small cavities
    • Compromise of bronchial and pulmonary Vascular supply
  • Pulmonary gangrene is the final stage if the necrotising pneumonia progresses uncontrollably
    • Characterised by sloughing of a pulmonary segment/lobe

Etiology

  • Staphylococcus aureus – particularly in young immunocompetent patients
  • Pneumococcus
  • Klebsiella pneumoniae
  • Pseudomonas
  • Haemophilus influenzae

Clinical features

  • Initially, typical symptoms of pneumonia
  • Systemic signs as disease progresses
    • Night sweats, weight loss, anaemia
  • Patient presents in hospital severely ill ± sepsis, with rapid clinical deterioration
    • Can show signs of septic shock
    • May need ventilator support

Pathogenesis

  • Simple lung abscess should drain spontaneously via the closest bronchus
  • NP has micro-abscesses, patchy inflammation with lack of perfusion
  • As the tissue undergoes liquifactive necrosis – the multiple small abscesses can coalesce to form larger cavities
    • Can progress to pulmonary gangrene

Diagnosis

  • Sputum + blood cultures – to identify causative pathogen(s)
  • CXR
    • Pts have more significant parenchymal disease, involving multiple lobes
    • Bulging fissures due to inflammatory exudation
    • CT thorax
    • Multiple small cavities <1cm
    • Normal architecture of lung is lost

Treatment

  • Early empirical antibiotics
  • Supportive measures – oxygen, fluids
  • Similar antibiotics to CAP – clarithromycin, co-amoxiclav, amoxicillin
  • Pneumococcal vaccination

Pulmonary Gangrene (can be difficult to distinguish from NP)

  • NP progresses to more severe parenchymal destruction, and eventually pulmonary gangrene (PG)
  • In contrast to simple lung abscess or necrotising pneumonia, PG has
    • Greater extent of necrosis
    • Obliteration or thrombosis of bronchial arteries (end arteritis obliterans)
    • Bronchial obstruction
    • In contrast to simple lung abscess, cavities in PG can lack the fibrous capsule
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