Post-pneumonic pulmonary pneumatoceles.

Abstract

Pulmonary pneumatoceles are areas of regional obstructive emphysema usually developing as a complication of staphylococcal pneumonia. They are thin-walled, air-containing, cyst-like structures which may occur at any age but are most frequently seen in infancy (Fig. 1). The majority of the recorded cases have been in infants and young children (1–4). Snider and Radner cite a few reports describing pneumatoceles in adults (5). The purpose of this paper is to report 20 cases in which pulmonary pneumatoceles developed as a complication of pneumonia; 8 of the patients were children and 12 were adults. The etiologic factor in most cases in both age groups was staphylococcal pneumonia. In view of the increase in the occurrence of this disease in the past several years we believe that it is important to understand the mechanism of development, roentgenographic appearance, and ultimate prognosis of pulmonary pneumatoceles. Mechanism of Development Pneumatoceles are believed to be the result of localized obstructive emphysema secondary to inflammatory narrowing of a bronchus. Potts and Riker (6) believe that their frequent occurrence in staphylococcal pneumonia is explained by the nature of the inflammatory process. It is their belief that a small area of necrotic lung is evacuated into a bronchus which is already narrowed by the inflammatory reaction and edema accompanying the pneumonia. The combination of a cavity communicating with a bronchus, narrowing of the bronchus by edema, and the normal expiratory bronchial constriction present an ideal combination of factors for the production of an area of obstructive emphysema. This small necrotic space then enlarges until a fully developed pneumatocele is formed. Clinical Features The most significant feature in patients with pulmonary pneumatoceles is the paucity or absence of symptoms after the pneumonitis resolves and the pneumatocele remains. All of our patients initially had clinical evidence of pneumonia and during this phase were symptomatic. As the pneumatocele developed, however, the pneumonitis usually resolved and the symptoms disappeared. At the time that the pneumatocele was fully developed, none of the patients had symptoms relative to its presence, and 18 of the 20 were completely asymptomatic. In the 2 exceptions the pneumonia was complicated by a pyopneumothorax. There is such a close relationship between staphylococcal pneumonia and pneumatocele formation that the development of an air space within an area of pneumonia should be suggestive evidence that a staphylococcal pneumonia is present. Wherever possible the etiologic organism was identified in our cases. Fourteen of the entire group, 5 infants and 9 adults, had proved staphylococcal pneumonia. Four had been treated prior to our observation and the causative organism was not recovered and in 2 cases the organism could not be definitely identified.