5-4-Air space filling disease

1-Replacement of alveolar air by fluid, cells, or other materials.

2-Represent an ongoing potentially treatable lesion.

3-Ground glass density is a geographic distribution due to morphologic changes below resolution of CT.

4-The end result of ground glass pattern is either interstitial or alveolar lung disease.

5-Chest clinicians have opinion that patients with ground glass pattern on CT chest, they will suffer from interstitial pulmonary fibrosis later on. So if they know that the patient has a ground glass pattern in his CT, they can start course of cortico-steroid to stop the process of fibrosis.

6-Air bronchogram sign:

-Air filled bronchi passing through opaque lung parenchyma(consolidation).

7-Types of air space filling diseases:

-Replacing the air by transudate---Pulmonary edema (clinical diagnosis).

-Pus         ---Pneumonia(clinical diagnosis).

-Blood      ---Hemorrhagic disorders(clinical diagnosis).

-Tumor cells---Alveolar cell carcinoma(diagnosed only by biopsy).

-Proteins    ---Alveolar protenosis(Imaging diagnosis).

8-Alveolar edema:

-Usually but not always, you can find in the chest film,ECG leeds of intensive care.

-You will find enlarged heart with air space filling disease of the lung.

-Lung disease is characterized by bat wing appearance which is central more than peripheral(there is a gap between the lesion and the pleura), and usually both wings of the bat are not equal if compared to each other as the lymphatic drainage on the left side is more rapid due to presence of thorasic duct than that on the right side, so the wing on the right side will be larger than that on the left side.

9-Diffuse pulmonary hemorrhage:

-Hemoptysis(not all the patient), anemia and air space filling disease.

-Appear rapidly and disappear after few days.

-Spare the lung apices and peripheral zones but not reaching central zone.

-Bilateral, may be asymmetric with air bronchogram.

-Repeated attacks cause pulmonary fibrosis.

10-Alveolar cell carcinoma:

-Radiographic patterns

*Single or multiple pulmonary nodules with air bronchogram.

*Segmental or lobar consolidation with air bronchogram.

*Diffuse air space disease.

*Nodule or mass with air bronchogram.

*CT angiographic sign(nonspecific).
*The most diagnostic sign of alveolar cell carcinoma is presence of bilateral lung nodules, some of them coalesce together to form patches, this appearance cannot be radiologically distinguished from pneumonia, we can differentiate both by giving treatment of pneumonia which does not response, so we can do biopsy to diagnose if it is alveolar cell carcinoma or not. 
 Presence of nodules on one side and patch on the other side can give an idea that this patch is due to alveolar cell carcinoma and not pneumonia.

Differential diagnosis of a pulmonary nodule or mass with air bronchogram.

-Round pneumonia.

-Alveolar cell carcinoma.

-Pulmonary lymphoma.

11-Alveolar protenosis:

-Alveolar filling by protenaceous material.
-Geographic distribution of areas of ground glass infiltration with thickened interlobular septae within its substance giving appearance of crazy paving sign.
-Air bronchogram is uncommon.
-In chest X-ray, it appears as a Bat Wing sign as that seen in alveolar edema, to differentiate between them just do CT chest to see characteristic crazy paving sign.