The clinical presentation of the patient with a lung abscess depends on the type of abscess. Patients with abscesses resulting from necrotizing staphylococcal or gram-negative bacillary pneumonias are usually acutely ill and exhibit clinical features of the underlying pneumonia. Although patients with primary lung abscess may also present acutely with aspiration pneumonia, they more often experience insidiously progressive symptoms for weeks or even months before diagnosis. Hemoptysis is present in approximately one third of cases and may occasionally reach life-threatening proportions. Chest pain consisting of either a dull ache or a true pleurisy is common.
Most patients have fever, but frank rigors are unusual.
In patients with a chronic course lasting many weeks, anorexia, weight loss, and debility are often seen. These findings are not diagnostic, however, and chest x-rays or CT scans are required to establish the presence of an abscess. Chest CT scans can define the extent of the abscess and, on occasion, may reveal an abscess not apparent on chest x-ray. Abscesses occur more often in the right lung than in the left lung. Although any lung segment may be involved, abscesses are most common in the posterior segments of the upper lobes and the apical segments of the lower lobes because these areas are dependent when the patient is recumbent.