Causes and prognosis of diffuse alveolar damage diagnosed on surgical lung biopsy

Background: Diffuse alveolar damage (DAD) is a relatively common histopathologic finding at autopsy, particularly in patients dying with ARDS, and can result from a variety of causes. The spectrum of causes and associated prognostic implications for DAD diagnosed by surgical lung biopsy are unclear. Methods: We identified 58 consecutive patients with DAD diagnosed by surgical lung biopsy over a 7-year period, January 1996 through December 2002. The presenting clinicoradiologic features, causes, and clinical course of these patients were studied. Results: The median age was 61 years, 48% were women, and 60% were immunocompromised. Ninety percent of patients fulfilled the criteria for ARDS at the time of surgical lung biopsy. Chest radiography demonstrated bilateral parenchymal infiltrates, while CT revealed predominantly ground-glass and consolidative opacities. Infections were the most common cause of DAD (22%). Other causes were noninfectious pulmonary complications of hematopoietic stem-cell or solid-organ transplantation (17%), connective tissue diseases (16%), acute exacerbation of idiopathic pulmonary fibrosis (12%), drugs (10%), and radiation therapy (2%). Twelve patients (21%) had acute interstitial pneumonia (ie, no identifiable cause or predisposing condition for DAD). Overall hospital mortality was 53%, with the highest mortality (86%) occurring among patients for whom DAD represented acute exacerbation of idiopathic pulmonary fibrosis. Conclusion: Our study showed that infections and acute interstitial pneumonia are the most common causes of DAD diagnosed by surgical lung biopsy. Hospital mortality rate associated with DAD may vary depending on the underlying cause.