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Interstitial Lung Abnormalities: When Are They Inc ...
Interstitial Lung Abnormalities: When Are They Incidental? When Are They Interstitial Lung Disease?
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So thank you guys for staying around for the last day. Thank you for joining us for interstitial lung abnormalities. So these are our learning objectives. We'll define what an ILA is, characterize why they're clinically relevant, identify features posing greater risk of evolution into interstitial lung disease, and then Lydia and Matt are going to take the wheel and discuss a lot of these imaging patterns in more detail to help you with your clinical practice. So faculty, I'm Sean Callahan, I'm at the University of Utah, Lydia Chalala, did I pronounce that correct? Perfect, is at University of Chicago, and Matt Koslow is at National Jewish. Not present today are Juliana Bueno and Jonathan Chung at UVA and UCSD, respectively, who helped with some of these slides in prior years. So this is me. These are my disclosures. They're not relevant to this talk. All right. And just as a reminder, we're going to have some audience response questions in here. So get your phones ready for answering some questions soon. All right. Let's jump right in. What is an ILA? This is the definition. It's a bit dry, but subclinical, high-density interstitial abnormalities, and importantly, they are subclinical. So they're kind of caught randomly as part of like a coronary angiogram CT or CT looking for PEs, lung cancer screening CT, but the patient doesn't have clinically relevant symptoms that are present. The patterns that you may see, things that count, are going to be cysts, honeycombing, reticulation, ground glass. They cannot be attributable to atelectasis, and they need to occupy 5% or more of a lung zone. For those of you who don't remember this, that's okay. This is pretty new. This is from a Fleischner white paper that came out three years ago, which really tried to help define this and help people when they see patients with ILAs. So this nomenclature of ILAs is pretty new, but know that this is not a new entity. We've known about this for decades, right? Like we get a CT scan, there's some incidental crap on there, we don't know what to do with it. People will call it like early ILD, preclinical ILD. That's what this is. It's just being called ILAs at this point. This is something to really keep an eye on. It's going to be a big research field in the next several years. This is a snapshot from PubMed from just a couple weeks ago, but you can just see like it's an exponential increase in the number of studies. I don't know why this tickled me so much, but I love the first quote here, best editorial title ever. Pinocchio, interstitial lung abnormalities and becoming a real disease. Just to decide. It's incredible. I want to meet Dr. Putnam and shake her hand. So for you guys to know, this can mean a lot of things. This is a spectrum. So I think when we think of ILA, what comes to mind are going to be these minor things that like they're there, what do we do with it, radiologists may or may not call it. That's what a lot of these are going to be. It's going to be some sort of mild, subtle finding. But what really distinguishes an ILA is it's subclinical. So it could be that a patient has a horrible looking CT scan like you see here on the right and they have no symptoms. That would still qualify as an ILA. So I work at the VA. I'm sure a lot of people in the audience work at the VA. I think half my patients could come in exsanguinating and they wouldn't have any symptoms. Like a lot of my patients with ILD in clinics say I'm doing great doc and their CTs look crappy like this. So I think it's incumbent on the practitioners in the room to look at the CT scan and try to decide is this an ILA that's just subtle or is this truly like an ILD I need to pay attention to. All right. I'm actually going to skip this for a second. Okay. All right. Which of the following statements is true regarding the epidemiology of ILAs? So it's not popping up on my screen, but you guys can read it. So advanced age have low rates of ILAs. Patients of advanced age who develop ILAs have low rates of progression. ILAs are present in 5-10 patients with a smoking history. Or ILAs may be present in 5-10 patients, 5-10% of patients without a smoking history. Okay, that's pretty good. Okay, ILAs may be present in 5 to 10% of patients without a smoking history. The correct answer is actually number three, or it's option three. So ILAs may be present in 5 to 10% of patients with a smoking history. We think that it's really pretty common, but your risk goes up, particularly with age and with smoking. So this is a really nice study from about seven years ago that looked at numerous large cohorts of patients, including from Framingham, Reykjavik study, COPD gene, and Eclipse, and found that in smokers, it's about 7 to 10% of patients will have ILAs. Really, I think it's important for you to look at the study in front of you and what that population's pre-test probability is. So people who are of advanced age, like the Reykjavik study, or patients who were in Eclipse, for example, they're all COPD patients, they're gonna have much higher rates of ILAs. Okay, so why does this matter? Like, we're defining this, we're adding more alphabet soup letters. Why do we care about this? Big picture, the reason we care so much is that these progress. You can look at lots of studies, they show high rates of progression. So this is, again, the Reykjavik study, so looking at a large population in Iceland, and in about 10% of patients, they found patients had ILAs, and about 3 quarters showed progression when they repeated a CT scan a few years down the line. Importantly, and this is true of nearly every study I'll bring up, when you have a patient with an ILA, it's a higher risk of death over whatever time horizon they're looking at. So a study from, I forget which country in Europe, but in Thorax, published last year, found actually a fairly low rate of what they would consider ILAs, compared to other studies, but of the people who had ILAs, it was pretty bad. Like, you can see the symptoms people had. A lot of people's had chest symptoms, crackles, cough, dyspnea. Their DLCO was clearly abnormal, and nearly half were diagnosed with progressive fibrotic lung disease. So when you, like, step back, look at it, these are pretty severe. About a quarter of patients were started on antifibrotics or immune suppression, so, like, real deal disease. It's a newer study from just this year in the Blue Journal, but they re-imaged patients with ILAs, and for years afterwards. So this is, like, over a decade afterward as a median follow-up, but over 3 quarters of patients had progressed. So they saw it, they followed it, nearly everybody got worse. What's particularly disheartening is about a fifth of patients ended up having a UIP pattern when they followed them long enough. So not only did it progress, it progressed to something that's bad. Like, we know this is bad, having UIP. What are the risk factors that associated with developing bad UIP patterns, or developing a UIP pattern? Honeycombing, and then larger areas of the lung that are involved. Oh, wow, look at how squiggly those red lines came out. Something didn't translate here. I think one thing to keep in mind is this, this is not just ILD progression. Like, keep in mind that this correlates with worse mortality. It does correlate with worse ILD progression, but it also is a marker of just, this patient isn't gonna do great, period. Like, when I was searching through the literature, preparing for this talk, there's stuff all over the literature. Like, they have worse COVID pneumonia, they don't tolerate their chemo as well, they don't get radiation as well, they develop more cancer. It's just a marker of badness. These patients are not gonna do as well. I've said this a few times now, but if you have an ILA, it's an independent predictor of higher mortality, and it seems to be somewhere around the range of a hazard ratio of, like, high ones or two. So, like, it's pretty legit. One particularly high-risk group to think about are patients who are prior smokers. So, a lot of your ILAs are gonna come from patients who are getting lung cancer screening CTs. If you're finding ILAs in somebody who's getting a lung cancer screening CT, respect it. Like, across all studies, we're finding that these are higher-risk patients if you find ILAs in them. Okay, let's identify some features that pose greater risk of evolution, and then after that, I'm gonna hand it over to Dr. Koslow. But first, another audience response question. All right, which of the following is a radiographic feature not associated with imaging progression? So, non-emphysematous cysts, abnormalities predominantly in the lower lobes, traction bronchiectasis, central lobular nodules, or subplural reticulation? Thank you. All right, pretty good. All right, you guys nailed it. So, central lobular nodules is the correct answer. So, big takeaway is, if somebody has features that look like pure scar, like definite fibrotic features, that's probably not gonna get better. So, you guys know what this is. So, traction bronchiectasis, honeycombing, if that's within something you're gonna call an ILA, that's not getting better, that may get worse. The best finding for an ILA you can find would be central lobular nodules, and the reason is, you know, a lot of these patients are smokers. It might be a fair amount of respiratory bronchiolitis. They also may be signs of infection. One thing that I discuss with our fellows when we see ILAs is, don't just have the one CT scan and look away. Like, you should really repeat these images and see what's gonna happen. That helps you with understanding the tempo of disease. It helps with risk prognostication. So, if you're repeating a CT, and this ILA is getting worse, that's not just helpful to say, okay, it's still there. If it's getting worse, that usually denotes a worse disease pattern in these patients. So, correlates with higher mortality, more symptoms, faster PFT decline. What are some clinical predictors? We've discussed several of these already, but older age and smoking. Couple others include male sex and elevated BMI. We're learning more and more that certain genetic risks, the MUC5 promoter polymorphism, seems to increase the risk. And then, being from Utah, where air quality is abysmal and the lake is drying up, higher levels of air pollution is of concern, too. All right, so how do we put it all together? I think big, big pictures look at this. So, look at the imaging. Risk stratify them. Are there more fibrotic features, or is there more inflammatory changes? Is it worse in the lower lobes? Is there more area involved? Clinical factors. I didn't discuss this at all, but if they have a family history, they're probably gonna behave like the family member. Are they older, are they smoke? Repeat a CT scan. Try to understand the slope. Try to understand the trajectory of their disease. That helps. If it's stable over time, it's gonna tend to behave the way it has, but if it's gradually getting worse, it's gonna keep getting worse. And then, check your pulse and think about the patient in front of you. Is this minor? Does the patient actually have an ILD that I'm just not appreciating, or they're not complaining of symptoms of? Sometimes you need to just take the wheel and be like, this is an ILD. We need to treat this. Just because you're not having symptoms yet, it may be that we need to start some treatment. All right. This is very helpful. These are the guidelines from the Fleischner Society white paper from a few years ago. Please use this. You know, it's based on expert opinion, but it makes sense. So, trying to risk stratify patients, repeat imaging, and doing clinical evaluations. And one thing for those of you who wanna learn more about this, this is a very active research field. Something that we may be seeing coming down the line, some investigators are looking at automated versions of looking at these. You know, it's hard for a radiologist to look and be like, eh, I guess that's 5% of a lung field. If we have automated imaging, we could probably get better at this. Combining this with clinical factors like do they have a hiatal hernia? You know, there's a great paper from Dr. Kim earlier this year looking at younger patients with ILAs. If they have hiatal hernias, it's gonna get worse. That makes sense. They're probably aspirating a bunch. But combining some other clinical factors that we don't even recognize yet may be helpful for risk prognostication. And then really, I think something that's gonna be key coming down the line is how do we combine this with genetic testing? We're getting better and better and better at the genetics of ILDs. So how do we incorporate that into our algorithms of thinking through CT scans? All right. All right, that's the end of my talk. Don't forget to evaluate the session in the app. Feel free to email me or ping me on Twitter. And I'm gonna hand it over to Dr. Kozlo. Thank you. Thanks, Sean. Okay, my name is Matt Kozlo. I have one major disclosure. I am not a radiologist, and this is a radiologist lecture. So Dr. Chalal is gonna correct things that I get wrong and maybe poke some holes where she needs to. Let's see. Oh, yeah. Okay. Many of these slides are courtesy of Dr. David Lynch and also Dr. Juliana Bueno who couldn't be with us today. So the focus of my part of this talk is to, there might be some overlap, but dig into that definition, what is an ILA, what's not an ILA, and give you some pictures. So what are we talking about? This is an example, just to set the setting. This is a 65-year-old woman, former smoker, quit over 30 years ago, 25 years ago, but she ended up for lung cancer screening. And you see, if you look really, really, really close, that there are fine, mild, reticular abnormalities in the subplural region. If Sean came up to me and said, Matt, I have this patient, what do you think, before I prepped for this lecture or before I knew about this subject, I'd be like, whatever, just forget about it. Probably long ago, but the issue is that we can't and this might be really important and we're gonna look at how this particular patient did over her course. So there might be some overlap here, but just to make sure we hone in our points. So another question, do I? There are a lot of people here for Wednesday afternoon. 48 votes, okay, 50, okay. All right, I'm going to go forward here. Great, and so you're picking up on that really important term, dependent. That's why we get prone imaging and we'll see an example on that. I think that's probably one of the most important take home messages. These other features are one of the high yield features that are associated with progression. So what is the definition of ILA? Sean went over this, but just to review, any area of increased lung density. So it's not just reticulation, also ground glass. Ground glass, reticulation, traction, honeycombing, and non-emphysematous cysts involves at least 5% of the lung zone. I have no idea what that means. I'll turn to Dr. Chalela to kind of explain that to me. And among patients who we don't suspect CTD, so not the scleroderma patient, not the occupational lung patient. The patient coming in for lung cancer screening or abdominal pain, something like that. So non-emphysematous cysts, we know the difference between a cyst and emphysema is that perceptible wall, not always easy to see. So you really have to ask your radiologist if you see paraceptal, what looks like paraceptal emphysema, is there a wall or is it not a wall? That's not always easy to see. Definitely not for me in the clinic on my little tiny screen. But here you can see that there are some airspace opacities here. You see this kind of outline. So giving that impression that there is a wall here, that this is not paraceptal emphysema. And then you see the progression over time in this particular patient. What is not an ILA? Dependent lung atelectasis, that's why we get prone imaging. Focal paraspinal fibrosis, very close to where the thoracic spine osteophytes sit. As Sean mentioned, smoking related central lobular nodularity in the absence of these other features. So if you have these other features, that's not going to qualify. But as a sole finding, yes, that is not a feature that's associated with progression. And then alternative diagnosis, whether that be heart failure or aspiration. And then as we just said, findings that are associated in high risk screening patients. So this is just a great example. We see this a lot. This is, you see very clear evidence of reticular markings, basilar subplural. But when we do the prone imaging, completely disappears. This patient does not have ILA, does not have radiologic disease, and does not have ILA. So that's more of a technical issue with dependent atelectasis. So that brings me to the, one of the main points in that Fleischner guideline is the imaging requirements to define an ILA. You should have thin sections. You should have prone imaging. And if you're doing this CAT scan, for the first diagnostic CT, you should have expiratory imaging, because that might further define characteristic features like air trapping. Background, Sean talked about this. I won't spend too much time, except for point two. It's really easy when you're in clinic and the patient says, I'm okay, doctor. And that's why we're clinicians. And you tie into that in every field, asthma, COPD, are they really okay? And there are certain clinical surveys that help ask that question a little bit better, like CAT for asthma. So I think we really have to make sure that they're not unrecognized symptoms. There is a higher relevance or association with impaired physiology with these patients, too. We know that this is a risk factor for mortality. Half the patients progress, and we're gonna talk about which patients are more likely to progress. So let's talk about this particular patient. 65-year-old woman, comes for lung cancer screening. This is her image in 2003. This was not reported in the radiologic impression. She came back to the ER. Five years later, totally unrelated issue, gets a lung window. You start to see evidence of traction. She does not have symptoms. Here she has symptoms. She comes back, gets a dedicated CT. She has symptoms. You see progression. You see more progression. And this is right around we're starting to get treatment for pulmonary fibrosis, but she passed in 2018. So just very illustrative of the main issue is of the Fleischner guidelines is to have a common terminology and to document these findings. So which patients are at risk for progression? So as Sean mentioned, this comes from the Iceland study and the main, we have on the top, the clinical features. Smoking didn't make it in there, which is interesting. The radiologic features associated with progression were what we would think in the UIP, probable UIP category. They're subplural. They are lower lung predominance. Lower lung predominance, traction. Honeycombing is not included because all, they couldn't calculate an odds progression because all patients with honeycombing progressed. And ground glass is not included here because all of these samples had ground glass. So it's not that it's not important. It is considered an ILA, but it wasn't one of the features that independently associated with progression. So just to make this more simple, when you see this CAT scan, we would think about this, whether they are nonplural versus subplural, and then the subplural dividing that into fibrotic features or nonfibrotic features. So this is an example of a non-subplural ILA, very indistinct ground glass. They're very, very fine nodularity. This was a smoker, and this was done incidentally. But this is an example of a non-subplural ILA versus the reticular and subplural findings, but we don't have features of, indirect features of fibrosis, no traction, no honeycombing. And then the subplural fibrotic ILA with the clear reticulation traction bronchiectasis here. So this, the purpose of the Fleischner was to have some common terminology because it can be very varied as Sean mentioned. So I think Dr. Shalala will talk a little bit more about this, but some complications, Sean also touched on this. In screening populations, ILA is associated with an increased risk of lung cancer. In patients with lung cancer, it's associated with worse outcome. And that might be worse outcome from treatment that they might receive. That might be worse outcome from the surgical resection that might happen. Drug toxicity, here's an example of an adenocarcinoma non-small cell on the right base. You see that post-resection. You have an increased of this, what looks like pulmonary fibrosis on the contralateral side in the setting of post-resection and chemotherapy. This is a patient diagnosed with COVID, and this is a CAT scan six months after her initial index diagnosis with COVID right here. We see signs of pulmonary fibrosis and ground glass abnormalities. However, she happened to have a CAT scan in 2014. Now, you can't see this because it is incredibly mild, but we analyzed that 2014, and this is what Sean was mentioning, of quantitative assessment or data textural analysis. It's an AI feature, and what it does is it tracks the extent of reticulation. We think that this AI feature is more sensitive and more specific to detection and rate of change, up to 4% range of variability, meaning that if you have, let's say, 5% and the next CT is more than 4 to 5%, that's probably reliably associated with progression. So just to touch on this concept of 5%, I am not confident of how you assess 5% when you do a visual assessment, and that's not a hard and fast rule at all, as you see in this case. And you can see, this is courtesy of Steve Humphreys, the marking here is the extent and distribution of that pulmonary fibrosis, up to 10%, and this is six months after that COVID diagnosis. So another question. So when you do diagnose an ILA, so in a patient with subplural non-pharbotic ILA, what would be management strategies? What include the following except? So what would be acceptable and which one would not be acceptable? Okay. Still impressed with the number of people here. Okay. Yeah, I would agree with choice D. I hope I didn't tie you up with the terminology here, but A, I think that would be acceptable and that's included in the FLY chart guidelines, repeating your clinical and physiologic assessment. Where we want to do that, that's somewhat variable, but getting them back to the clinic. When to repeat an imaging, that's certainly would be, I think, up to the clinician and the patient, but probably you don't want to let two years pass. So no clear recommendation, but the recommendation is something around 12 to 24 months. Screening for other features that may lead or contribute to disease progression, whether that be smoking, whether that be occupational risk exposure. Certainly aspiration can be a risk factor for disease progression. D, reassess if symptoms or other evidence of progression. I think that's the key feature here is the patient might not come back. So you want to bring the patient back. You want to try to see if there are any unrecognized symptoms, do physiology, but you don't want to let this go. So getting to the end of my talk, we want to use appropriate language for reporting ILA. We want to be consistent. We want to document this so we can track these features. The findings are non-subplural, subplural, and then fibrotic and non-fibrotic. What we want to do if we have a CT abdomen or a non-high resolution CT, at that point we want to make a diagnostic CT. The imaging requirements are thin cuts, prone imaging, and I think usually we're going to do expiratory imaging. But the main issue is getting that prone imaging, physiologic assessment, and looking for any potential underlying causes that might make this not an ILA. So does that patient have scleroderma? Does that patient have a family history of pulmonary fibrosis? That would put you now in a high-risk category. So take-home points, I think we're looking for a critical approach to how to assess these incidental findings. That ILA, as Sean mentioned, is a risk factor for certain complications from disease treatment, whether that be thoracic surgery or any kind of cardiothoracic surgery. And then we want sequential long-term follow-up, especially for these radiologic features that correlate with disease progression. Okay, I'm going to turn it over now to Dr. Shalala. Hi, everyone. Thank you for having me. I'm going to talk a little bit more about the radiologic features of ILA. There will be some overlap with Sean and Matt, but we'll look at a few cases, and hopefully this will illustrate a little bit more the points that were already discussed. Jonathan Chung was instrumental in putting this talk together, so I wanted to acknowledge him and acknowledge one of the pulmonary fellows at University of Chicago, who has been a very key person in looking at these patients and managing them. These are my disclosures. So first of all, why are ILAs relevant? We already talked about this, but in a proportion of patients, these are reflective of undiagnosed early ILD or subclinical ILD that would eventually progress to overt ILD. We also know that they are associated with increased all-cause mortality, as well as increased morbidity in certain patients, including patients with COPD and patients with lung cancer on treatment. Despite being important, they are oftentimes under-recognized and under-reported, and so it is really important for us to increase our familiarity with these findings. Even more so when they are recognized, they don't necessarily lead to a pulmonary referral in most of the patients. So in our diagnostic approach, when we're assessing findings on chest CT, our first step is to determine whether findings are actually reflective of ILA or not. If ILA is present, a detailed description is ideally provided. Key terminology, adequate terminology is actually very important because it will allow us to find features that would predict prediction, progression, sorry, and it will impact management and the need for active monitoring. So briefly in this talk, I will go over the definition again. I will discuss some of the high-risk features, and I will briefly talk about adjunct tools for the qualitative assessment on chest CT. Matt and Sean already talked about this, what are ILAs? ILAs are incidental. They're non-dependent abnormalities that we see on chest CT in patients who did not have suspected ILD, and they supposedly involve more than 5% of any lung zones. This 5% threshold, Matt, is arbitrary. It's really a subjective assessment when we're looking at these chest CTs, and it's used to exclude patients with minimal abnormality. Lung zones, what are lung zones? They're basically just arbitrarily defined as three lung zones in each lung. They're defined by the inferior level of the aortic arch and the superior level of the inferior right pulmonary vein. When we are describing ILA on imaging, we are using specific terms, descriptors that you're probably familiar with. Of these descriptors, honeycombing, traction bronchiectasis, and architectural distortion are considered to indicate fibrotic ILAs, and this is particularly relevant for subplural ILAs. So beyond these very simple descriptors that you just saw, we define ILA by describing its relationship to the pleura as either subplural when it's hogging the pleural linings, or non-subplural when the immediate subplural lung is spared. We also define it on imaging as limited when two lung zones or less are involved, or as extensive when there's involvement of three lung zones or more. If subplural fibrotic ILA is present, we need to classify the pattern based on the Fleischner and ATS guidelines as either typical UIP, probable for UIP, or indeterminate for UIP. The typical and probable UIP patterns are similar in that they're subplural lower low predominant patterns with some fibrotic features. The distinguishing feature between typical and probable UIP is the presence of honeycombing in the typical pattern. An indeterminate pattern is basically a non-UIP pattern that's not suggestive of a specific etiology. So I thought we could look at a few cases and determine whether we think the patients have ILA or not. This first patient is a female patient who presented for weight loss. The team was trying to figure out whether there was an underlying malignancy. And you can see on the CT images, lower low predominant subplural honeycombing shown by these blue circles. The abnormality is superimposed on a reticular pattern. The reticular pattern extends beyond two lung zones. And so this was considered to be a typical UIP pattern of interstitial lung abnormality. And this young patient who presented with a history of sarcoma, we were trying to assess for anematostatic disease. The initial chest CT showed some dependent ground loss opacity, so if you look at these images, you can actually see these areas of increased density in the more dependent lungs. And it seemed like they persisted on the follow-up CT, at least in part. In general, I think Matt touched on this, but dependent abnormalities are considered equivocal for ILA unless they persist on prone imaging. So what we usually do when we're assessing these patients is we acquire prone and expiratory sequences ideally. And so on the prone sequence in this patient, you can see total resolution of the ground loss opacities in the dependent lower lobes. And so this was compatible with analectosis rather than ILA. This was a patient with rheumatoid arthritis presenting with chronic cough. So just looking at the history, we are already skeptical of the findings that we're seeing. You can see a substantial honeycombing in the upper lobes and the lower lobes. Looking at the multi-planar reconstruction is really helpful in any case of ILA or interstitial lung disease as well. And these multi-planar reconstructions show very nicely the anterior upper and posterior lower lobe predominance of the findings. This is what we would usually call a typical UIP pattern. And because of the history of this patient, this patient was considered to have rheumatoid arthritis associated ILD. Generally speaking, in patients with a high risk, including patients with connective tissue disease, patients with familial fibrosis, patients with occupational exposures, if similar findings are found on chest CT, they're typically considered to be ILD rather than ILA. This is another patient who was asymptomatic from a pulmonary standpoint, had a history of colon cancer, was being followed up to exclude metastatic disease. I'm not really sure if you can see this very nicely, but the patient has these very faint but fairly diffused centrilobular ground glass nodules that you can see across the axial and the coronal images. The patient was actually a smoker, and so this was considered to be respiratory bronchiolitis. So this particular nodularity is not considered to be an imaging feature of interstitial lung abnormality. This is another female patient who presented with chronic cough, and so the patient had an initial chest CT done in 2011. The follow-up CT 12 years later shows sort of a progression of a focal abnormality that we're seeing in the paramediastinal right lower lobe. So initially you see this subplural density on the follow-up imaging. This focal honeycombing in this area, the coronal projections also show these findings very nicely. The location of the findings, the appearance both on the initial and subsequent CT and the presence of adjacent osteophytes that you can see here in the spine are all very typical of what we call osteophyte-related fibrosis. Again, this is not a case of interstitial lung abnormality. This is a female patient who was complaining of some vague chest discomfort. In her history, she had a gastroesophageal reflux disease, and looking at these images here we see some patchy groin glass opacity asymmetrically involving the left lower lobe. There's some mild associated bronchiectasis, so you can see the airway is slightly bigger than the adjacent vessel. On the subsequent chest CT, there's some improvement of those groin glass opacities. Generally previous studies have shown that some of the equivocal and non-fibrotic ILAs could potentially improve, but not the fibrotic types of ILA. We proned the patient and we saw persistence of the findings. This was considered equivocal for ILA. The reason why is because any mild unilateral or focal abnormalities are usually considered equivocal. We thought that this could be related to aspiration given the patient's clinical history. This is another patient with progressive shortness of breath. PFTs were pseudonormal. I'm sure you guys can tell me more about that. On the imaging, you can see these very dense subplural opacities of the lung apices. On the left, there's more substantial bronchiectasis associated with the findings. There's a little bit of uplifting of the major fissures that suggests that there is some upper lobe volume loss associated with these findings. This is very typical of what pleuroparenchymal fibroelastosis looks like on CT. This is, again, a pattern that's not compatible with interstitial lung abnormality. I just wanted to go over these cases to show some patterns that would be equivocal or not compatible with ILA. ILAs are also known to be very common. I think Sean mentioned that they can be present in about 10% of patients that are being screened for lung cancer. They're fairly more prevalent than your IP-IPF, which makes us think that not all of them are actually clinically meaningful. When are they meaningful? When do we need to worry about them more? Imaging can help us assess the risk of progression. Findings on imaging that have been associated with a greater likelihood of progression are the presence of reticulation and the subplural fibrotic ILAs, particularly the probable and the typical UIP pattern more than the indeterminate pattern. I wanted to go over a few cases to see if we could actually predict the progression on imaging. This was a patient with intermittent cough, had an initial chest CT that showed these very fine reticular densities in the lower lobes. No overt fibrotic features, no traction bronchiectasis, no honeycombing. The patient comes back about six years later, and you can see that there's a little bit of increased extent of the subplural reticulation, and there's also some very mild traction bronchiolectasis in the azigoesophageal recess being shown by this arrow here. We pruned the patient because this was done as an ILG protocol, and you can see persistent of the findings. You would expect that the presence of reticulation would lead to a greater risk of progression, and this is what happened in this patient. Now in this other patient, in contrast, similarly we see some subplural reticulation in the lower lobes. You also see them on the sagittal projection, and they seem to be involving three long zones. There were no fibrotic features, so this was considered to be a nonfibrotic subplural ILA. Reticulation again infers theoretically a greater risk of progression, but in this patient we actually did not see progression on a chest CT that was done about three years later. In this patient, a female patient who had a low-dose CT that showed ILA, we got a repeat study to assess for any changes, and the findings are suggestive of a typical UIP pattern. You can see some mild honeycombing in the right lower lobe. There's also a reticular background that's predominantly involving the lower lobes, but there's no significant change on the one-year follow-up CT. These coronal images also show the stability of the reticulation in the lower lobes, but when we went back and looked at a prior abdominal CT that was done in 2020, we saw that there was actually a little bit of progression compared to the earlier CT. So this was a typical UIP pattern of ILA that had progressed, and this is compatible with what we know and read in the literature. In contrast, this is another patient that was initially being evaluated for peripheral artery disease. The patient had an initial chest CT done in 2013 that showed lower lobe predominant reticulation. You can see some traction bronchiectasis. The areas are too prominent at the periphery of the lungs. There's also some volume loss in the lower lobes that's suggested by these displaced fissures bilaterally, but there was no substantial change about a decade later, so in 2023, no real progression of this pattern that we would have called probable UIP in the beginning. I added this prone image just to show you that there was no substantial honeycombing in the lower lobes in this patient. Yet another patient, a history of prostate cancer. Initial CT was an abdominal CT done in 2013 that we looked at retrospectively that showed really very minimal subplural reticulation and the costophrenic angle laterally in the right lower lobe. There was some mild dependent ground loss that we thought was just allelectasis. So really minimal equivocal ILA. Fast forward about nine years later, you start to see some honeycombing in the right lower lobe, more reticulation, more traction bronchiectasis. It's shown nicely on the coronal image by this blue arrow. And so this minimal equivocal ILA actually progressed to a typical UIP pattern of ILA a few years later. In contrast in this patient who had mild but more extensive subplural reticulation and very mild traction bronchielectasis, we obtained on a follow-up CT an expiratory phase that showed air trapping. So this is on your right-hand side a minimum intensity projection that's showing these lobular areas of hypodensity. This is what is usually called air trapping. The pattern was considered to be indeterminate for UIP. This was a subplural ILA that was considered to have mildly fibrotic features, but it did not progress on the subsequent CT. And so the sagittal images here also are showing stability of the findings. This is the last case that I'll be showing today, but I think it's a fairly interesting one. This is a female patient who initially presented with pleuritic chest pain. A PE study was obtained because the team thought she could have an acute pulmonary embolism. And back in 2021, we saw these ground glass opacities that were lower lobe predominant. If you look at the immediate subplural lung, you can see that there is some subplural sparing and very mild bronchiolectasis at the edge of the lungs, particularly in this right middle lobe and the right lower lobe. Initially the patient was thought to maybe have COVID-19 pneumonia, but the test came back as negative. And a couple of years later, actually, we see these findings on the repeat chest CT, a more reticular pattern, again, lower lobe predominant. We're now seeing overtraction bronchiolectasis, so an overt fibrotic pattern. In the interim, the patient had been diagnosed with scleroderma. You can see this prominent esophagus. So this was actually an early scleroderma ALG case. So these cases or these examples show you that we're still finding a lot of challenges in stratifying ILA on imaging. It's not reliable all the time. And we know from our experience in ILD that our qualitative assessments are limited. They're limited in the sense that we have substantial intra- and intra-observer variability in the assessment of these cases, even when experienced chest radiologists are involved. Matt also talked about this earlier, but we're also not very sensitive in finding subtle changes on follow-up CTs. So if it's really subtle, it's very difficult to see it on our visual assessment. And these limitations of qualitative methods have pushed the advances that we've been seeing in quantitative tools. These quantitative tools, their applications have been expanded not only for the diagnosis, but also for the quantification, the prognostication, and the monitoring of ILAs and ILDs. But there is still a lot of work to be done to validate many of these algorithms and to implement them more consistently in the clinical workflow. In conclusion, imaging is a very valuable asset in assessing these ILAs. And hopefully in the future, a greater role of quantitation will allow us to become more reliable and more reproducible in assessing these findings. Once ILA is identified, it should ideally trigger a more extensive clinical workup to determine which patients will actually benefit from active monitoring and more aggressive management. And I think that this is all for me. This is my email if you would want to ask any questions. Thank you.
Video Summary
Interstitial lung abnormalities (ILAs) are incidental, non-dependent abnormalities seen on chest CT scans that involve more than 5% of any lung zone. They can be characterized by various imaging patterns, including cysts, honeycombing, reticulation, and ground glass opacities. ILAs are often clinically relevant as they can be a subclinical indication of early interstitial lung disease (ILD) and are associated with increased risk of progression and higher mortality.<br /><br />The assessment of ILAs involves a detailed description of the imaging findings, including the location (subplural or non-subplural) and extent (limited or extensive) of the abnormalities. Subplural fibrotic ILAs can be further classified into typical UIP, probable UIP, or indeterminate patterns based on the presence of honeycombing. High-risk features such as reticulation and fibrotic ILAs are associated with a greater likelihood of progression. Repeat imaging, clinical evaluation, and assessment of symptoms are crucial for monitoring ILAs and identifying patients who may require active management.<br /><br />Quantitative assessment tools and algorithms are being developed to improve the reliability and reproducibility of ILA assessment. These tools can aid in diagnosis, quantification, prognostication, and monitoring of ILAs and ILDs. Validation and implementation of these algorithms in clinical practice are ongoing.<br /><br />Overall, recognizing and accurately characterizing ILAs on chest CT scans is important for identifying patients at risk for ILD progression and mortality, and for guiding appropriate management and monitoring strategies.
Meta Tag
Category
Diffuse Lung Disease
Session ID
1029
Speaker
Juliana Bueno
Speaker
Sean Callahan
Speaker
Lydia Chelala
Track
Diffuse Lung Disease
Keywords
Interstitial lung abnormalities
ILAs
chest CT scans
imaging patterns
subclinical indication
interstitial lung disease
mortality
quantitative assessment tools
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