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Good afternoon everyone. Thank you so much for joining me.

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Today I want to talk to you about just a common dilemma we're

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often faced with every day at the workstation when we're looking at a

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chest CT, sometimes in the acute setting, sometimes in a lung cancer screening

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setting if you report those, or just in an outpatient setting, incidental

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finding. And that is an unexpected finding where you're thinking to yourself

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could this be a malignancy that needs to be worked up?

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Could this just simply be infection that we can follow?

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Or even is this just simply atelectasis? And

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these are quite basic questions but I think we face this every day

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and some of these questions can be very challenging on a case by

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case basis. So I hope by sharing some of these cases and going

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over how I think about these cases and the details I look for

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to help me decide it will help you have confidence in making

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these decisions during your practice. Okay, so I'll share our first case.

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So this is a relatively young man in his 40s who presents with

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right sided back pain and this was a CTPA, query pulmonary embolism,

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which he did not have. And there is this additional finding that we

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can see here. As you can see, this is not a normal CT

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of the lungs. I'll just scroll through and let you

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have a look at it and see what you think. And then we'll

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have our first question. So coming through, and I'll put on long windows.

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All right, so can we have our first question?

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So the question is, what is the most likely diagnosis? Is this pneumonia?

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Is this atelectasis? Or is this cancer? Okay, so we're pretty divided here

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40% saying pneumonia, 33% saying atelectasis, and 22% saying cancer. So

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let's go through and I'll show you what I'll look at and then

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I'll give you a little bit additional information

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after going into the EMR. You find this additional information and then

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we'll ask the same question again. So as I look at this,

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let me go back to soft tissue windows.

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Well, refresh on the long windows, one of the things I notice is

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that, well, there's an effusion, right? It looks a little bit loculated.

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It's not completely layering. And there's quite a lot of ground glass opacity,

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right? And I think when we say ground glass opacity, a lot of

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us can feel like we're a deer in headlights and we immediately think,

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is this COVID? But when I see ground glass opacity that's fuzzy and

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ill defined and hard to draw a line around, one of the first

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things I think of is inflammation. So this looks to me like there's

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an inflammatory process going on in the lungs. And that's a similar finding

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to what we might see in the abdomen. I sort of started off

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as an abdominal imager actually, so I think I bring a lot of

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that perspective to my chest reading when we see fat stranding,

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we often think inflammation. And I think you can look at some of

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this sort of ill defined ground glass opacity similarly.

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The second thing I'll do is look at the way the lung is

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enhancing. So if we go back to soft tissue windows, we can see

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that there is some enhanced lung. And atelectatic lung will typically enhance

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brightly, right? So we know that the lung is very vascularized.

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This is where oxygen exchange happens. And if we take all the air

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out, what we're left with is just very little lung tissue and a lot of

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vascular spaces. So normally, atelectatic lung will enhance very brightly.

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And so as I go through, I see some lung that's enhancing really

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brightly, but other areas of lung are not enhancing very well.

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And so that to me indicates that there are either cells, fluid,

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pus, or blood in there. And in this case, I'm thinking,

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well most likely cells and fluid as an infection.

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The effusion here, we can see it a little bit better on soft

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tissue windows. There's not really any plural thickening

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or enhancement to suggest there's an empyema. However, there is a little

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bit of loculation. And if we're thinking that, which I'm at this point,

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thinking this is probably an pneumonia because of hypoenhancing lung inflammation

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and fluid, then if we understand the process of developing an empyema, going

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from a simple reactive effusion adjacent to an pneumonia to a developing

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complex effusion with some loculations to a frank empyema with

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enhancing pleura, this seems to be in the intermediate phase. So this is

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a complex effusion, which isn't maybe yet an empyema, but would eventually

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become one likely. So this is an pneumonia

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by my reading of the CT scan. Another thing that I think goes

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for pneumonia is the fact that it's multifocal. So

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it's involving both lower lobes and the right middle lobe and the right

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lower lobe. So multifocality is often a finding favoring infection inflammation

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rather than neoplasm. The last thing I like to look at,

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and this is not a perfect case for this, is to look at

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the airways. So typically pneumonia and atelectasis will not occlude airways,

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whereas... Airways. Similar to the way cancer will occlude vessels

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and structures elsewhere in the body. If you have a carcinoma, it will obstruct

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the biliary tree. If you have a pancreatic cancer, it will often obstruct

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the portal vein. So cancers in the lung will also obstruct vessels and airways.

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And here we can see that this right lower lobe bronchus is coming

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down, and there's a little bit of bubbly stuff within the bronchus. That's

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mucus, and they do disappear and that's a finding I don't love for...

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That's not a finding I love for infection. However, overall, the rest of

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the findings look like pneumonia to me. So I decided, okay,

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I'm going to go ahead and look in the chart, and I find

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out that the white blood cell counts 21 with neutrophils 84%.

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So let's have question 1b. So we've looked at a few specific findings

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on the CT, and we've also taken advantage of the chart,

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which is right there. And very quickly, we didn't spend time reading all

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the notes, but we did see that the white cell count is up

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in the left shift. Right, so I mean, I pretty much told you that

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it was pneumonia. But yeah, but I think you get the point.

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That there are some really specific findings that we can see on the

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CT, and then if we marry that with some of the clinical information,

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we can make a much more confident diagnosis. And so in this case,

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appropriate for this patient would not be to get a full,

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say a CT scan of the abdomen and pelvis looking for metastatic disease

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or to get a biopsy, but rather to

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be treated with antibiotics and get a follow up CT and a follow up with

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this patient completely cleared.