Necrotising pneumonia (NP) refers to a pneumonia characterised by the development of the necrosis within infected lung tissue. While the term has sometimes been used synonymously with a cavitating pneumonia in some publications 2, not all necrotising pulmonary infections may be complicated by cavitation.
Necrotising 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 paediatric population.
Progression to a necrotising 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.
- Klebsiella pneumoniae 6 - see - klebsiella pneumonia
- Enterobacter sp
- Nocardai sp - see - pulmonary nocardia infection
- Actinomyces spp - see - thoracic actinomyces infection
- Pseudomonas spp - see - pseudomonas aeruginosa pneumonia
- Pneumococcus spp - especially type III pneumococcal sp 3.
- Haemophilus influenzae - pulmonary haemophilus influenzae infection 8
If a necrotising 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 liquifaction 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 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 necrotising pneumonia 10. In some centres, 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
- necrotising pulmonary malignancy 7
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