Aspiration of oro-pharyngeal secretions and gastric content is the most frequent cause of formation of primary
lung abscess. A compromised mental status (e.g.
alcoholism,
sedatives,
stroke) and esophageal dysfunction (e.g. herniation,
vomiting) are important risk factors.
Aspiration pneumonia presents as a subacute disease and is usually not distinguishable from other causes of
pneumonia, until typical radiological signs of cavitation and putrid sputum appear 8 to 14 days after the initial event of aspiration. Anaerobic bacteria play a pivotal role in an almost exclusively mixed spectrum of causative organisms. Aerobic pathogens are also frequently isolated, but whether they are an active part of
infection or merely represent colonizers remains unclear in many instances. Differential diagnosis includes
bronchial neoplasms, either as necrotizing
carcinoma or as the cause of poststenotic cavernous
pneumonia, other
infectious diseases like
tuberculosis,
Pneumocystis carinii pneumonia or
endocarditis with septic
metastases, and lung artery
embolism or
vasculitis (M. Wegener). Fiberoptic bronchoscopy is extremely helpful in determining cause and etiology of the disease and should be carried out in all patients presenting with cavernous lung lesions. Bacteriological sampling should be performed using protected specimen brushing (PSB) technique. Broncho-alveolar lavage might serve as a less expensive but also less sensitive alternative measure. Since anaerobic bacteria resemble ubiquitous commensals of the oral cavity, sputum is of no use in anaerobic culture. Principal therapeutic strategy is
antibiotic therapy for an extended period, usually four weeks to four months, unless radiologic changes and as well laboratory as clinical indicators of
infection are completely resolved.
Clindamycin, optionally supplemented with a second or
third generation cephalosporin and
Ampicillin/Sulbactam proved equally effective in treating
aspiration pneumonia and primary
lung abscess. The role of
Moxifloxacin and other new flouroquinolones with their favorable pharmacodynamics is currently evaluated. Provided that
antibiotics are prescribed for a sufficient period of time and patients' compliance is ensured,
surgical procedures are limited to a negligible number of complications, e.g. recurrent severe
hemoptysis,
empyema or broncho-pleural
fistula.