Quik Case 2:

1- Interstitial opacity could be in the form of reticular; nodular or reticulo-nodular pattern.

2- It could be isolated or accompanied with alveolar opacity; perilymphatic nodular distribution or both.

3-If it is isolated or with peri-lymphatic nodular distribution look for its type if it is smooth or coarse.

4-If it is coarse think about fibrosis as first possibility and look if it is more prominent in the upper or lower lung.

5-D.D. upper lobe interstitial lung disease:
-T.B.
-Histoplasmosis.                        2 H& 2S
-Silicosis.
-Sarcoidosis.
-Hyper sensitivity pneumonitis.
-Radiation pneumonitis.
-Ankylosing spondylitis.
-Lung rejection.

6- Perilymphatic nodular distribution:

The distribution of the nodules will be in the following pattern:

-Peri broncho-vascular distribution.
-Fissural dist.
-Septal dist.
-Sub pleural dist.

Finally coarse reticulo-nodular diffuse lung disease with prominent upper lung, fibrosis; perilymphatic nodular distribution is equal to Sarcoidosis.

If it is formed of reticulo-nodular diffuse lung disease with prominent upper lung, fibrosis; perilymphatic nodular distribution  in addition to air space opacities (consolidation) and cavities some of them with fluid level and bronchiectatic changes with thickened wall is picture equal to T.B.