Abstract Multifocal ill-defined opacities most often result from multiple consolidations but must be distinguished from invasive or hemorrhagic tumors. This is not a common appearance for community-acquired pneumonia, but when it occurs this appearance indicates a serious infection that is likely caused by a virulent organism. Patients with a documented viral infection such as influenza who develop this pattern have most likely developed a superimposed bacterial pneumonia. Multifocal air space opacities are a common appearance for hospital-acquired pneumonias, especially for patients in the intensive care setting. Fungal pneumonias should be considered when the chest x-ray is suggestive of pneumonia and cultures for bacterial infection are negative. Immune compromised patients are at high risk for aggressive fungal infections. Multifocal air space opacities are not a common appearance for tuberculosis, but it must be excluded in patients who either present with associated cavities or develop cavities. Invasive mucinous adenocarcinoma is the most likely tumor to have this appearance and must be considered in an afebrile patient with a chest x-ray that looks like a multifocal pneumonia. This is a rare appearance for chronic lung diseases, but it may result from sarcoidosis, cryptogenic organizing pneumonia, hypersensitivity pneumonitis, and silicosis or coal worker’s pneumoconiosis.
16 Multifocal Ill-Defined Opacities