What is diffuse alveolar hemorrhage (DAH), and what is its imaging appearance?
DAH is a potentially life-threatening condition that occurs when blood products fill the alveolar spaces. Clinically, patients will often present with hemoptysis, although this will not be present in up to one third of patients. In the absence of hemoptysis, bronchoscopy or biopsy may be required to establish the diagnosis. Nonspecific laboratory markers include anemia and thrombocytopenia.
Major causes of DAH include vasculitis (such as granulomatosis with polyangiitis), systemic lupus erythematosus, Goodpasture’s syndrome, and bleeding diatheses (such as with hematologic malignancies [leukemia, lymphoma], coagulopathy, or disseminated intravascular coagulation).
DAH typically manifests as widespread ground glass opacities with or without areas of consolidation that tend to spare the lung apices and periphery. Sometimes, the ground glass opacities can appear nodular and centrilobular in distribution. Intermixed areas of septal thickening, or a crazy paving pattern, may also be present. Despite the name, DAH can be localized or multifocal rather than diffuse in distribution. When diffuse, DAH is often radiographically indistinguishable from pulmonary edema or ARDS.