Pulmonary gangrene

Histologic changes: There is a sharp transition from normal lung to the blackened area, which shows consolidated air spaces with preserved outlines (coagulative necrosis). Alveoli are filled with necrotic exudate. The blackening was caused by oxidative changes that occurred during life in the infarcted, infected tissue. There was no evidence of organization within or around the gangrenous tissue.

Liquefactive necrosis, noted as small cavities radiographically and grossly, was present only focally. Inflammatory cells were sparse even at the margin.

The bronchus and artery to the segment were both occluded. A Gomori methenamine silver (GMS) stain showed this organism. What is it? Answer

Several large arteries showed an arteritis and thrombosis even when fungi were not visible. This artery (between arrows) has a necrotizing, destructive angiitis and luminal thrombosis.

Pulmonary Gangrene (syn: Spontaneous amputation or lobectomy, massive sequestration or necrosis)

Introduction: Pulmonary gangrene is caused by a combination of infection and infarction. It differs from necrotizing pneumonia or abscess in its extent--usually a whole segment or lobe. It is usually caused by bacteria (mostly gram negative), but fungi, tuberculosis, and radiation can also cause it. Anerobic infection may be superimposed on the initial infection. A review of 25 cases indicated that most cases (76%) occurred in men. The mean age was 47 y (range 21-83). Predisposing factors included chronic lung disease, alcoholism, diabetes mellitus, and nutritional deficiency. The upper lobes were involved in 80% of cases. The architecture of the necrotic lung is usually preserved, at least in part, suggesting that enzymes causing liquefaction are absent. If the patient can muster enough PMNs, peripheral liquefactive necrosis can isolate a portion of lung--a so-called "sequestrum" [1]. A case similar to the one reported here had a 3-month course and was diagnosed as chronic necrotizing pulmonary aspergillosis [2].

Radiographic findings: Initially, a consolidated area becomes cavitated. Sometimes an air crescent sign or large cavity develops [1,3]. CT can show whether the associated bronchus is patent or collapsed. If patent, the necrotic lung can be expectorated, and surgical drainage may not be necessary [1].

Diagnosis: If a parapneumonic empyema, which usually occurs, persists and the patient appears toxic despite antibiotics and drainage, pleuroscopy showing a blackened lung that does not expand with respiration is diagnostic [3].

Histologic changes: Gangrenous lung is characterized by thrombosis of a large artery and coagulative, as well as variable liquefactive, parenchymal necrosis in the setting of pneumonia [1]. Tissue oxygenation via both blood and airways is abolished.

Treatment: Unless the necrotic tissue is expectorated, drainage is mandatory. A two-stage procedure has been recommended. Antibiotics and drainage of empyema are continued until infection abates. Then the gangrenous lung can be excised, if necessary. Survival rates with these procedures can be excellent [3,4].

References

1. Penner C, Maycher B, Long R. Pulmonary gangrene. A complication of bacterial pneumonia. Chest 1994; 105:567-573.

2. Yamaguchi M, Nishiya H, Mano K, Kunii O, Miyashita H. Chronic necrotising pulmonary aspergillosis caused by Aspergillus niger in a mildly immunocompromised host. Thorax 1992; 47:570-571.

3. Refaely Y, Weissberg D. Gangrene of the lung: treatment in two stages. Ann Thorac Surg 1997; 64:970-974.

4. Odell J. Invited commentary. Ann Thorac Surg 1997; 64:973-974.

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Answer: The organisms are septate hyphae that branch dichotomously at an acute angle. The most likely diagnosis is aspergillus, but because Pseudallescheria boydii and some other fungi have a similar appearance, culture is necessary to confirm the diagnosis. Cultures yielded A. fumigatus.