Interstitial Disease (Part 1)

00:01 So now let's discuss interstitial disease.

00:03 Interstitial disease is filling of interstitial spaces which are different than consolidation which is filling of the alveolar spaces.

00:12 Interstitial disease can be either focal or diffuse.

00:16 It's not confluent so you don't see patches of consolidation.

00:20 You see specific linear areas within the lungs which don't coalesce and you won't see air bronchograms in interstitial disease.

00:29 Let's take a look at the three major patterns of interstitial disease.

00:34 You could have a reticular pattern and we'll look at each of these in a little bit more detail.

00:39 You can have a primarily nodular pattern or you can have a reticulonodular pattern, so a mix of the two.

00:46 So let's take a look first at the reticular pattern.

00:50 Reticular patterns can be divided into two different types.

00:53 You could have a coarse reticular pattern or you could have a fine reticular pattern and this shows you the difference between the two.

00:59 So the left image shows you what a coarse reticular pattern looks like and it's just a little bit more dense, it's a little bit more irregular than a fine reticular pattern is.

01:08 Fine reticular patterns can be caused by a multiple different reasons, primarily interstitial edema and that's the most commonly seen and that is caused by fluid in the interstitial spaces.

01:18 Infection can also cause a fine reticular pattern and that's usually a result of an atypical infection such as a viral infection, mycoplasma, or PCP.

01:28 It can be caused by lymphangitic spread of tumor.

01:31 The most common tumors to cause this pattern are breast, pancreatic, lung, or stomach, or it can be idiopathic such as an interstitial pneumonia and usually in these cases the end stage is pulmonary fibrosis.

01:43 So this is an example of interstitial edema or fluid in the interstitial spaces.

01:47 You can see that there is a very fine reticular pattern, so you can see these very linear opacities that are present within the lungs.

01:54 You don't see any area of focal consolidation just these very fine prominence of the interstitial spaces.

02:01 Infection is another example as we said usually caused by an atypical infection and so this is again a very similar finding with prominence of the hilum bilaterally and again the very fine reticular pattern that we saw similar to that interstitial edema. Often it's difficult to distinguish between the different types of fine reticular patterns and normally what we say is that there's interstitial disease and then clinically the referring physician can decide whether or not this is infection or edema or any other possibility that may be present in this patient.

02:32 So this is an example of lymphangitic spread of tumor.

02:35 Again, we said the most common tumors that can cause this pattern are breast, pancreatic, lung, or stomach and this results usually in a more of a mixed reticulonodular pattern.

02:44 So this is an axial CT scan of the chest and lung windows demonstrating prominence of the interstitial spaces.

02:50 You can see the difference between the right lung which has this prominence and the left lung which is actually clear.

02:57 So you can see this diffused haziness and again linear markings branching throughout that lung and then you also see small areas of nodularity which is typical of this mixed reticulonodular pattern.

03:08 This is an example of an idiopathic pneumonia.

03:12 So chronic interstitial pneumonia, the most common is the usual interstitial pneumonia but there are actually many different types of idiopathic pneumonias and as we mentioned end stage is usually pulmonary fibrosis.

03:21 So you can see here predominantly in the periphery, you have these areas of prominence of the interstitium and you have a little bit of thickening of the pleura which is commonly seen in these pneumonias.

03:34 On the radiograph it's actually a little bit less visible because it is somewhat focal to the periphery.

03:40 So here we see a sharp margin at the costophrenic angle and it's really the CT that tells us what's going on.