Interstitial Lung Disease (ILD) in a Nutshell

[Music] hello everyone it's Eric strong from Stanford University and strong medicine and today I'll be giving an overview to interstitial lung disease also known as diffuse parenchymal lung diseases after the video you'll be able to describe the classification ideologies presentation and diagnostic evaluation of interstitial lung disease first though what is interstitial lung disease ILD is not one specific condition but rather refers to any disease affecting the pulmonary interstitial in common usage however the term typically excludes infectious and neoplastic diseases pathologically most ALDS are characterized by a combination of interstitial inflammation and fibrosis as well as alterations of alveolar and airway architecture if you've tried to study and understand il DS before and have been frustrated by them you are not alone this is a frustrating topic partially due to lots of acronyms and constantly evolving terminology the lack of a universal and logical classification system doesn't help different systems place different weights on historical precedence clinical presentation radiographic and histological appearances biological mechanisms and treatment what I'm going to show is my preferred way to classify these diseases which may not be the most common way that pulmonologist and pathologist classify them but which makes more sense to me as a more general clinician I think about there being four main categories of disease the first are those directly caused by exposures of some kind in this category are hypersensitivity pneumonitis also known as extrinsic allergic alveoli tiss this condition is caused by an immune mediated response to inhaled organic dust there are many subtypes of hypersensitivity pneumonitis based upon the inhaled substance and which is generally named not after the associated microbe but rather the occupation or hobby of the individuals who tend to get it so for example so-called farmers lung caused by proximity to moldy hay and bird fanciers lung caused by proximity to bird feathers or excrement there are many many others next under the general category of exposure related ILD are the pneumoconiosis these are il DS caused by inhalation of inorganic substances the main substances implicated here are coal dust scene and miners asbestos seen in construction workers shipbuilders and auto mechanics particularly those who work on auto breaks silica seen in miners quarry workers and stone carvers and beryllium seen in a variety of industrial jobs radiation pneumonitis occurs as a consequence of radiation treatment for intrathoracic cancers and the number of medications have been implicated as a potential cause of ILD in particular the anti rhythmic amiodarone the antibiotic natural fear and toen and the amino suppressive drug methotrexate in the next broad category of IL DS are those secondary to connective tissue diseases which are systemic autoimmune conditions these include systemic sclerosis rheumatoid arthritis mixed connective tissue disease polymyositis and dermatomyositis and lupus of these systemic sclerosis is the most likely to cause Ald and lupus is the least likely next are the so called idiopathic interstitial pneumonias this is the category that learners and clinicians both find to be the most difficult to keep straight because they have very similar presentations differing only in time course they have a poorly understood pathogenesis and they have kind of ridiculous names which are often abbreviated into acronyms they are idiopathic pulmonary fibrosis nonspecific interstitial pneumonia cryptogenic organizing pneumonia respiratory bronchiolitis interstitial lung disease d-square motive interstitial pneumonia and acute interstitial and the last category is the miscellaneous one here we have sarcoidosis vasculitis - in particular granulomatosis with polyangiitis and the various similarly named eosinophils granulomatosis with polyangiitis also known as jerk strauss syndrome there is a significant ammonia which has both acute and chronic forms some classification systems actually leave this one out and last pulmonary Langerhans cell histiocytosis so you can probably appreciate how some of the terminology feels a bit impenetrable making this more complicated is the fact that with idiopathic pulmonary fibrosis the term refers to the clinical entity while the histologic pattern seen in IP F is called usual interstitial pneumonia or uip so you might have a pathologist saying this patients lung biopsy shows you IP consistent with IP F and then on top of all this the radiographic and histologic appearances of the idiopathic interstitial pneumonias can be seen with other diseases but when this happens the names are only used to describe the pathology so for example rheumatoid arthritis related Ald is most commonly associated with a usual interstitial pneumonia histology and radiographic appearance but you would not call it IP f if it's associated with RA likewise systemic sclerosis is most commonly associated with an NS IP pathologic and radiographic appearance finally while we have all the ideologies up on the screen at once let me label those which are observed almost solely in current or past smokers which includes RBI LD d IP and pulmonary Langerhans cell histiocytosis so all of that terminology that was the hard part of the video now let's talk presentation ILD should be considered in any patient presenting with symptoms of sub acute or chronic progressive dyspnea and/or a non-productive cough particularly if they have a history of occupational irrelevant animal exposure which does not include dogs and cats connective tissue disease just irradiation or the use of medications such as amiodarone nitro phenytoin or methotrexate due to their diverse nature il DS also have a diverse presentation regarding age sex and racial predominance relationship to smoking history family history acuity of onset and radiographic appearance however there are some commonalities as mentioned the symptoms common to all il DS are dyspnea and a non-productive cough common exam findings include hypoxemia which might only be present during exertion and find crackles sometimes described as dry or velcro-like in contrast to the wet coarse crackles of bronchiectasis and bacterial pneumonia fever is common in hypersensitivity pneumonitis and sarcoidosis but is otherwise uncommon clubbing is generally only seen in advanced idiopathic pulmonary fibrosis and if observed in a patient was relatively mild ILD it should prompt an investigation for a possible lung malignancy the presence of extra pulmonary symptoms or exam findings is suggestive of a connective tissue disease vasculitis or sarcoidosis hemoptysis chest pain and wheezing are all relatively uncommon symptoms though they certainly can occur for example hemoptysis is a well described presentation of granulomatosis with polyangiitis now let's talk time course over how long do these diseases typically progress before the patient seeks medical attention and the diagnosis is hopefully made I'm going to focus on five of the more common diagnoses first hypersensitivity pneumonitis has an enormous range from an acute illness developing just hours after a single heavy exposure to a chronic insidious form developing over years the ILD is seen in sarcoidosis typically develops over weeks to many months radiation causes to clinically distinct il DS acute radiation pneumonitis occurs about one to three months after radiation exposure while a chronic form of radiation pneumonitis sometimes called radiation induced pulmonary fibrosis occurs about 6 to 12 months after radiation idiopathic pulmonary fibrosis develops over many months to several years and last are the pneumoconiosis which typically take many years to develop and become clinically apparent so once a clinician has identified a patient as possibly having an ILD what type of diagnostic evaluations should occur first a very detailed exposure history needs to be taken this includes the patient's current and prior occupations and their hobbies asking about any potential chemical inhalations if there may have been also asked about the use of a respirator or if they have noticed their symptoms improve on the weekends or while on vacation when the exposures would not have occurred for several days ask about exposure to animals particularly Birds ask about medications illicit drugs as well such as smoking marijuana and feta beans or crack cocaine and last of course prior radiation treatments the four key diagnostic tests to consider include a high resolution chest CT the high resolution part of it refers to the thickness of the cuts the thinner of the cuts the better the ability to diagnose Ald pulmonary function tests should be ordered including not just Barama tree but also lung volumes and in most cases a test called the diffusing capacity of lungs for carbon monoxide abbreviated dlco bronchoalveolar lavage and lung biopsy are performed in some but not all patients and is often considered when an ILD is rapidly progressing and the need to confirm a suspected diagnosis is urgent let's talk about the possible findings on lung imaging although I did not mention plain chest x-rays as a key diagnostic test almost all patients with suspected Ald will for one reason or another get a chest x-ray prior to CT so when discussing ILD it's helpful to have a basic handle on the relevant radiographic terminology as a very general rule the appearance of interstitial opacities can be further described based on their pattern a chest x-ray may demonstrate a reticular pattern meaning there are too many liens within the lung fields it's sometimes described as net-like it may demonstrate a nodular pattern consisting of too many dots or if there are too many lines and too many dots to a roughly equal extent it's described as reticular not here on the left is a patient with a predominantly reticular pattern from early pulmonary fibrosis and for comparison on the right is a predominantly nodular pattern from silicosis as my inclusion of the word predominantly may imply most chest x-rays in ILD have some degree of both particular and nodular patterns and the descriptive term chosen is based upon the subjective impression of whether one of the two patterns is more prominent than the other when it comes to the high-resolution CT there are a large number of potential findings some more specific than others they include grand class capacities which refers to regions of increased attenuation within the lung meaning it looks whiter while not totally obscuring the airways and vessels so for example on this axial cross-section through the thorax here is normal lung tissue and here are the ground glass opacities there can also be consolidations which are regions of more significant attenuation in which the Airways and vessels are obscured there is a less common but related finding called crazy paving named after the stone tile pattern in this finding there are ground glass opacities as well as superimposed inter lobular and intra lobular septal thickening resulting in patchy and well demarcated regions of grayness within the lung tissue the CT can show nodules of a wide diversity of size and appearance a finding that is more specific for interstitial lung disease is honey coming in honey coming there are clusters of cystic air spaces typically basal and posterior and distribution this is most commonly associated with idiopathic pulmonary fibrosis this particular C team also shows traction bronchiectasis which is irreversible dilation of bronchi and bronchioles generally thought to be due to mechanical traction on the airway walls as a consequence of the surrounding fibrosis I'll move from radiographic tests to pulmonary function tests all ALDS have similar findings on PFT s there is a restrictive pattern on spirometry meaning that the patient has a normal or slightly low fev1 which is the volume exhaled in the first second of the patients most rapid expiration there is a low fvc or forced vital capacity which is the difference in the patient's lung volume between the maximal inspiration and maximal expiration and a normal or elevated fe b12 fvc ratio this last finding helps to distinguish ILD from obstructive lung diseases like COPD in which the fe b12 FBC ratio is abnormally low on a flow volume loop which typically accompanied spirometry the loop is much smaller than normal though the peak expiratory flow is normal or only mildly reduced and unlike in COPD there is no inward coving of the expert ory limb of the loop when measuring lung volumes I already mentioned that the FBC or vital capacity is low but also all of the lung volumes are typically low including the inspiratory reserve volume tidal volume expert ory reserve volume and residual volume with the net consequence of reduction in the total lung capacity and if diffusion capacity is measured it will show a load dlco which means that gasses have difficulty diffusing across the alveolar at capillary membrane the general mechanism of the observed hypoxemia so now using all that information what is the general approach to making a specific ILD diagnosis a differential diagnosis can be generated by combining the clinical history that is the time course smoking history and other exposures in the extra pulmonary physical findings that might be suggestive of a connective tissue disease vasculitis or sarcoidosis the presence of specific CT features keeping in mind that some CT findings occur more commonly in some diseases than others and the distribution of disease as determined by CT such as a precedes versus paces diffuse versus sub plural and central lobular versus Perry lymphatic versus random occasionally a B Al and or lung biopsy may be necessary to confirm a diagnosis and the P of T's will helpful in establishing the presence and severity of an interstitial lung disease do not help distinguish il DS from one another that's it for this video on ILD please remember to like and share it if you found it helpful and if you have not already seen them you may find my similar videos on COPD and the interpretation of P of TS to be helpful as well [Music]

Channel: Strong Medicine

Views: 99,913

Rating: 4.8624935 out of 5

Keywords: ild, dpld, pulmonary fibrosis, ipf, hypersensitivity pneumonitis, radiation pneumonitis, idiopathic interstitial pneumonia, medical education, medical school, restrictive lung disease, sarcoidosis, langerhans cell histiocytosis, silicosis, black lung, coal miner's lung

Id: EqGT7IgUHU8

Length: 16min 49sec (1009 seconds)

Published: Tue May 07 2019