If the organizing pneumonia is secondary to a connective tissue disorder, then the associated laboratory values such as the anti-nuclear antibody, rheumatoid factor, anti-citrullinated protein antibodies, anti-dsDNA antibodies and other similar connective tissue associated antibodies are elevated.Pulmonary function testing in people with organizing pneumonia, either cryptogenic or due to secondary causes, shows a restrictive defect with a decrease in the gas absorptive capacity of the lungs (seen as a decrease in the diffusion capacity of carbon monoxide). Airflow obstruction is usually not seen on pulmonary function testing.Bronchoscopy with bronchoalveolar lavage is recommended in possible cases of organizing pneumonia to rule out infection and other causes of alveolar infiltrates. The bronchoalveolar lavage in organizing pneumonia shows a lymphocytic predominant inflammation of the alveoli with increases in neutrophils and eosinophils. Resolution of inflammatory cells in the bronchoalveolar lavage is usually delayed in organizing pneumonia, lagging behind clinical and radiographic improvement.Biopsy findings in patients with organizing pneumonia consist of loose connective tissue plugs involving the alveoli, alveolar ducts and bronchioles. The loose connective tissue plugs occupying the alveolar spaces often connect to other connective tissue plugs in nearby alveoli via the pores of Kohn creating a characteristic butterfly pattern on histology. There is usually minimal to no interstitial inflammatory changes in biopsies of organizing pneumonia. Imaging
The chest x-ray is distinctive with features that appear similar to an extensive pneumonia, with both lungs showing widespread white patches. The white patches may seem to migrate from one area of the lung to another as the disease persists or progresses.
In 1983, Robert E. Marx, a prominent oral and maxillofacial surgeon, refuted the notion that trauma and infection were requirements in the development of ORN. Marx proposed that ORN was the result of cumulative tissue damage caused by radiation, creating disturbances in cell metabolism and homeostasis that resulted in cell death and hypocellular tissues. In addition, radiation causes injury to the endothelial cells of local vasculature, creating a hypovascular environment which leads to decreased oxygen delivery resulting in hypoxic tissues. The decrease of vasculature helps explain why the mandible is more commonly affected than maxilla, as the mandible is served primarily by the inferior alveolar artery, whereas the maxilla is served by various arteries and has a more robust blood supply. In sum, Marx believed that ORN was essentially hypocellular-hypovascular-hypoxic tissues behaved much like chronic non-healing wounds. Initial reports by Marx and others showing that treatment with hyperbaric oxygen (HBO) prevented ORN helped support this theory. However, later studies began to raise doubts about the effectiveness of HBO therapy and question whether Marxs theory was comprehensive enough to guide treatment.Current understanding is guided primarily by the work of Delanian and Lefaix, who proposed the radiation-induced fibroatrophic (RIF) process. Advances in lab techniques allowed scientists to perform more detailed studies of ORN specimens. Analysis of samples showed that tissues undergoing ORN underwent three phases of disease: 1) prefibrotic, 2) constitutive organized and 3) late fibroatrophic phases.