necrotizing pneumonia

School ager
with feverCXR shows near complete opacification of the left hemithorax. Axial and coronal CT with contrast of the chest shows dense collapsed left upper lobe lobe and less dense collapsed left lower lobe with an even lower density cavity forming within it and a large left pleural effusion without definite pleural enhancement.The diagnosis was bacterial necrotizing pneumonia.
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Necrotizing pneumonia refers to pneumonia characterized by the development of the necrosis within infected lung tissue.

Terminology

While the term has sometimes been used synonymously with cavitating pneumonia in some publications , not all necrotizing pulmonary infections may be complicated by cavitation.

Epidemiology

Necrotizing changes may be seen in ~7% of those with bacterial pneumonia . It can affect patients of any age and is increasingly being reported in the pediatric population.

Pathology

Progression to necrotizing pneumonia can occur from either virulences factor of the microorganism, predisposing factors of the host or both.

It can result from a large number of pathogens, which include:

  • Staphylococcus aureus
    • ​particularly in young immunocompetent patients
    • this ability to cause lung necrosis appears to be intimately related to the secretion of the Panton-Valentine Leukocidin (PVL), a pore-forming cytotoxin present in the majority of community-associated Methicillin-resistant Staphylococcus aureus (CA-MRSA) isolates, which assembles as a ring pore in the membrane of the host leukocytes, leading to leakage of cell contents and ultimately leukocyte necrosis and a superantigen effect
  • Klebsiella pneumoniae (Klebsiella pneumonia)
  • Enterobacter spp.
  • Nocardia spp. (pulmonary Nocardia infection)
  • Actinomyces spp. (thoracic actinomyces infection)
  • Pseudomonas spp. (Pseudomonas aeruginosa pneumonia)
  • Pneumococcus spp.: especially type III Pneumococcal sp. 
  • Haemophilus influenzae (pulmonary Haemophilus influenzae infection)

Radiographic features

CT

If a necrotizing infection is suspected and CT evaluation is required, it may be better to give contrast as it allows appreciation of low attenuation and non-enhancement within the necrosed portions.

CT imaging may show distinct areas of low attenuation with decreased parenchymal enhancement (representing liquefaction ) in all or parts of the affected area of infection (consolidation).

Normal pulmonary parenchymal architecture within the necrosed segment is often lost .

Treatment and prognosis

Treatment depends on the underlying agent while prognosis depends on the severity of the pathogen as well as the susceptibility of the host. In general, complete recovery can be anticipated in children with bacteremic necrotizing pneumococcal pneumonia contrary to what is seen in adults .

As opposed to a formed lung abscess, interventional procedures (e.g. drainage) may be counterproductive in cases of necrotizing pneumonia . In some centers, pulmonary resection has been carried out as a surgical option .

Differential diagnosis

For a lesion with large areas of low intrinsic low attenuation, consider:

  • lung abscess: more well-defined with little surrounding consolidation
  • necrotizing pulmonary malignancy

See also

Siehe auch:
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