Focal necrotizing pneumonia is a distinct entity from lung abscess

Background and objective: 'Focal necrotizing pneumonia' was defined as a localized type of necrotizing pneumonia characterized by a single or few cavities of low density without rim enhancement on computed tomography (CT) scan. The purpose of this study was to investigate the clinical features and course of patients with focal necrotizing pneumonia, thereby elucidating its clinical relevance. Methods: The present study was conducted retrospectively in patients who had been interpreted as having lung abscess or necrotizing pneumonia on CT scan. Clinical and radiological characteristics were compared between the focal necrotizing pneumonia and lung abscess groups. Results: Overall, 68 patients with focal necrotizing pneumonia (n = 35) or lung abscess (n = 33) were included in the present study. The frequency of risk factors for aspiration was significantly lower in the focal necrotizing group, compared with the lung abscess group (14.3% vs 45.5%, P = 0.005). Compared with lung abscess, focal necrotizing pneumonia was observed more commonly in non-gravity-dependent segments (66% vs 36%, P < 0.001). In addition, a trend towards more common isolation of aerobes as potential pathogens was observed in the focal necrotizing pneumonia group, compared with the lung abscess group (31% vs 12%, P = 0.08). However, in terms of treatment outcomes, a similar high rate of success was observed in both groups: 97%, respectively. Conclusions: Compared to lung abscess, focal necrotizing pneumonia occurs more commonly in non-gravity-dependent segments with lower incidence of risk factors for aspiration. Similar to lung abscess, the rate of success for treatment of focal necrotizing pneumonia was high.