So a coarse reticular pattern is usually caused by pulmonary fibrosis.
This is also referred to as honeycomb lung
because of the presence of coarse reticular opacities
with intervening cystic spaces so it produces the appearance of a honeycomb.
Usually this result in progressive volume loss,
we have what's called traction bronchiectasis so widening of the bronchi
because of pulling from the fibrosis that's surrounding it
and this often results in end stage lung disease.
So the most common causes include as we mentioned idiopathic interstitial pneumonia
but other causes could also include sarcoid, collagen vascular disease,
different types of drug reations, or it maybe idiopathic.
Let's take a look at the different findings of pulmonary fibrosis.
So on the left we have an example of a radiograph that's coned down to the right lower lung
and you can see coarse reticular markings.
You can see them outlined here by the arrow,
so again, very coarse reticular markings you can see them appear as well,
just prominence of the interstitial spaces.
On the right two images we have honeycombing and traction bronchiectasis.
So let's take a good look at each of these.
So here we have a better example of what honeycombing could look like on a radiograph.
So you can see prominence of this interstitial with an intervening cystic space right here.
You also see prominence of the interstitial markings up here outlined by the circle.
On this we have an example of honeycombing,
again with prominence of the interstitial markings
and intervening cystic spaces causing the appearance of a honeycomb.
And this last image shows a dilated bronchus.
Again, this is an example of traction bronchiectasis
so we have surrounding scarring and fibrosis which pulls on the bronchi
and causes them to enlarge.
So the remaining two types of pattern seen with interstitial disease
are nodular and reticulonodular.
So we've seen in the example of reticulonodular with metastatic disease.
Let's take another look at some examples.
So other things that can cause a reticulonodular pattern
or a nodular pattern are hematogenous metastases
which can spread through the bloodstream and again the common causes are renal cell,
testicular, breast, colon, melanoma, sarcoma, and ovarian.
These usually produce more of a nodular pattern and somewhat less of a reticular pattern.
So this is an example of varying nodules of different sizes.
You can see them throughout both lungs and this is an example of hematogenous metastases.
So you can see the interstitium actually looks somewhat normal here.
It's really just the multiple nodules that we see.
So on a chest x-ray, whenever we see multiple nodules
like this one of the things that should come to mind is metastasis.
Bronchogenic carcinoma can also produce this pattern.
This is an example that I'm about to show you of an adenocarcinoma of the right upper lobe.
So although lung cancer can produce multiple different nodules,
usually the initial presenting sign is the single large nodule like we see here.
You can see that it's pretty well circumscribed
and this can be confused with the consolidation
so usually to differentiate what we would do is we would treat the patient
if there's any thought that this might be a pneumonia.
You would treat the patient with antibiotics
and then do a follow up chest x-ray to make sure that the finding has resolved.
So tuberculosis can also cause multiple nodules.
This is an example of primary tuberculosis.
You can see that there is multifocal consolidation,
rarely you may see a cavitation and usually if it is in, it's at the right upper lobe
and you can also see ipsilateral hilar lymphadenopathy.
Primary TB can also produce pleural effusions which we don't see on this radiograph.
So reactivation TB can produce a different pattern upon presentation.
This is usually caused by reactivation of a primary focus that's acquired during childhood.
Usually, this presents with consolidation, often cavitary that are localized to the upper lobes
and the superior segments of the lower lobes.
Here you can see the bilateral upper lobe consolidation.
Healing usually results in fibrosis so you can see another area of consolidation here
involving the lingula and the left upper lobe.
Sarcoid can also present with multiple interstitial nodules.
So sarcoid initially present with bilateral hilar and right paratracheal lymphadenopathy
and it often has a mixed reticular and nodular interstitial pattern.
You can see the adenopathy here on this radiograph.
So sarcoid initially presents again with adenopathy,
later on it then moves on to adenopathy and interstitial disease
and usually it ends with primarily interstitial disease.
Lymphoma is another factor that can cause interstitial nodules.
Fungal infections also appear very similar
and again when you take a look at all of these nodules
it's often difficult to differentiate between one versus the other.
Clinical picture really has to be taken into account
and the only thing you can really say sometimes looking at a chest radiograph
or a CT is that there are multiple nodules
and then we use the clinical information to better differentiate among them.