Case 3
History
The patient is a 37-year-old alcoholic with fever and pleuritic chest pain.
PA chest radiograph shows cavitating masses with
fluid levels in both lungs of intermediate wall thickness.
Follow up PA chest film one week later demonstrates
right lower lobe thick walled cavity measuring 7 mm
with an irregular inner lining.
Findings
The term “abscess” is usually used for cavities that result from pyogenic infection. Staphylococcal pneumonia in adults will cavitate in 25 – 30 percent of cases. Gram negative organisms will cavitate with greater frequency, especially Pseudomonas and Klebsiella. Aspiration is usually the source of mixed gram negative and anaerobic organisms. The major sources of anaerobic infections are the oropharynx and paranasal sinuses. A lung abscess may develop as a result of any bacterial pneumonia, but abscesses are particularly common after aspiration.
The terms “cavity” and “abscess” are not synonymous. An abscess will appear solid until there is communication with the bronchial tree, which allows drainage of the necrotic debris. The radiologic result is a lucent cavity with an air fluid level. Cavitation that is seen in infectious disease is likely secondary to bacterial toxins and enzymes released by leukocytes, which then leads to tissue necorsis. The radiologic features of the cavity wall cannot be reliably used to distinguish abscess from carcinoma since there is a great deal of overlap with regard to cavity thickness and character of the inner lining. The typical radiographic pattern is usually segmental homogenous consolidation and subsequent cavitation indicating an acute necrotizing pneumonia. The cavities are usually thick walled and may be multiple if the pneumonia is multilobar. Differential diagnosis includes neoplasm, post infarction, fungal disease, or tuberculosis.
