Diagnosis and therapy of abscess forming pneumonia

Abstract

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.