Necrotizing pneumonia refers to pneumonia characterized by the development of the necrosis within infected lung tissue.
While the term has sometimes been used synonymously with cavitating pneumonia in some publications 2, not all necrotizing pulmonary infections may be complicated by cavitation.
Necrotizing changes may be seen in up to around 7% of those with bacterial pneumonia 3. It can affect patients of any age and is increasingly being reported in the pediatric population.
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:
- 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 ref
- Klebsiella pneumoniae (Klebsiella pneumonia) 6
- Enterobacter spp.
- Nocardia spp. (pulmonary Nocardia infection)
- Actinomyces spp. (thoracic actinomyces infection)
- Pseudomonas spp. (Pseudomonas aeruginosa pneumonia)
- Pneumococcus spp.: especially type III Pneumococcal sp. 3
- Haemophilus influenzae (pulmonary Haemophilus influenzae infection) 8
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 4) in all or parts of the affected area of infection (consolidation).
Normal pulmonary parenchymal architecture within the necrosed segment is often lost 2.
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 4.
As opposed to a formed lung abscess, interventional procedures (e.g. drainage) may be counterproductive in cases of necrotizing pneumonia 10. In some centers, pulmonary resection has been carried out as a surgical option 12-13.
For a lesion with large areas of low intrinsic low attenuation, consider:
- lung abscess: more well-defined with little surrounding consolidation
- necrotizing pulmonary malignancy 7
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