EXERCISE 4-9. CAVITARY DISEASE
4-14. The chest radiographic findings (Figure 4-43 A, B) in Case 4-14 could be best explained as
A. multiple lung abscesses due to Staphylococcus aureus.
B. pneumatoceles due to Pneumocystis jiroveci pneu-monia.
C. Wegener’s granulomatosis.
D. multiple cavities due to Mycobacterium avium-intracellulare.
E. metastases from Kaposi’s sarcoma.
4-14. PA and lateral chest radiographs (Figures 4-43 A,B) and CT images (Figure 4-43 C,D) show at least two thick-walled cavitary lesions in the right lung (C is the correct answer to Question 4-14). There is no hilar or mediastinal lymph node enlargement. The heart and skeleton are normal.
Inflammatory lesions are the most common cause of lung cavities (Table 4-9). The number of cavities may range from one to many. A wide variety of infecting organisms may re-sult in cavitation, and the radiograph is nonspecific as to eti-ology. There is considerable overlap in appearances from the various organisms, so that culture or histologic evaluation is the only satisfactory means of identifying the etiology. If the lesion is single, a cavitating pneumonia should be the first consideration, especially if the patient is febrile. If multiple cavities are present (Figure 4-44), the infection is likely due to hematogenous dissemination, and a source for this dissemi-nation should be sought. The source could be right-sided en-docarditis or infected venous thrombi. Staphylococcus aureus pneumonias are frequently seen in intravenous drug users and usually appear as multiple cavities. These usually have thin walls (2 to 4 mm) that are slightly indistinct on their outer borders.
As the acquired immunodeficiency syndrome (AIDS) epi-demic has progressed, it has been recognized that patients with Pneumocystis jiroveci may develop cavitary lesions in the lungs (Figure 4-45). These cavities may be reversible and re-sult from pneumatoceles, or they may be due to a slowly pro-gressive granulomatous reaction. The cavities are usually in the upper lobes and are thin walled. Pneumothorax can result when a peripheral cavity ruptures through the visceral pleura, into the pleural space.
Neoplasia, either primary or secondarily involving the lung, may also cavitate (see Figure 4-39 C). Cavities may re- sult from pulmonary vasculitis, of which Wegener’s granulo-matosis is the prototype. Demonstrating the importance of clinical history, the supplied history of renal disease points toward Wegener’s granulomatosis.