Rapid progression from initial symptoms to respiratory failure is a key feature. An x-ray that shows ARDS is necessary for diagnosis (fluid in the small air sacs (alveoli) in both lungs). In addition, a biopsy of the lung that shows organizing diffuse alveolar damage is required for diagnosis. This type of alveolar damage can be attributed to nonconcentrated and nonlocalized alveoli damage, marked alveolar septal edema with inflammatory cell infiltration, fibroblast proliferation, occasional hyaline membranes, and thickening of the alveolar walls. The septa are lined with atypical, hyperplastic type II pneumocytes, thus leading to the collapse of airspaces. Other diagnostic tests are useful in excluding other similar conditions, but history, x-ray, and biopsy are essential. These other tests may include basic blood work, blood cultures, and bronchoalveolar lavage. The clinical picture is similar to ARDS, but AIP differs from ARDS in that the cause for AIP is not known. File:CRIM.PULMONOLOGY2012-678249.001.Acute<unk>  pneumonia showing a marked reduction in lung capacity File:Acute<unk>  pneumonia (AIP) Idiopathic DAD 3.jpg File:Acute<unk>  pneumonia (AIP) Idiopathic DAD 2.jpg File:Acute<unk>  pneumonia (AIP) Idiopathic DAD.jpg
Acute interstitial pneumonitis
Acute eosinophilic pneumonia
Swimming-induced pulmonary edema
Cryptogenic organizing pneumonia
Chemical pneumonitis
Atypical pneumonia
Idiopathic interstitial pneumonia
Malignant pleural effusion