The ICU chest film: cardiac versus pulmonary disease.

We have discussed several diseases that diffusely affect the pulmonary parenchyma. The diagnostic problem is to separate cardiac pulmonary edema from noncardiac pulmonary edema, diffuse interstitial fibrosis, and lymphangitic spread of carcinoma. Frequently, this may not be possible by radiographic means alone, and additional historic and physiologic information must be obtained. It is also important to know that cardiac pulmonary edema may present in a focal or regional distribution in patients with chronic obstructive pulmonary disease. Several additional radiographic tests may be used to evaluate abnormal pulmonary parenchymal densities seen on the portable chest radiograph, when the differential diagnosis includes increased extravascular water, pneumonia, and pulmonary fibrosis. The easiest of these tests to perform is the gravitational shift test.