Diffuse alveolar hemorrhage.

Diffuse alveolar hemorrhage represents a medical emergency, and clinicians must have an expedient approach to its identification. There are many causes of diffuse alveolar hemorrhage, including vasculitides, immunologic conditions such as Goodpasture's syndrome, collagen vascular disease, and idiopathic conditions. Careful attention to the medical history, physical examination, and targeted laboratory evaluation often suggests the underlying cause. Patients in whom the diagnosis of diffuse alveolar hemorrhage remains uncertain should undergo diagnostic bronchoscopy. In patients with evidence of diffuse alveolar hemorrhage and renal involvement, kidney biopsy should be considered to identify the underlying cause and help direct therapy.