Survey
* Your assessment is very important for improving the workof artificial intelligence, which forms the content of this project
* Your assessment is very important for improving the workof artificial intelligence, which forms the content of this project
3 LOBAR COLLAPSES Lobar collapses occur due to occlusion of major bronchi. This occurs secondary to sputum plugs/ inhaled foreign bodies or tumours. Understanding the appearance of collapsed lung is simply a case of under standing the anatomy involved. Important anatomy of the bronchi. The right main bronchus is more vertically orientated than the left main bronchus which is almost horizontal in orientation. The angle between them averages out at about 65 degrees. This means inhaled foreign bodies are ore likely to go down the right main bronchus. The right main bronchus divides into and gives off the upper lobe bronchus, it then continues downwards as the bronchus intermedius. The bronchus intermedius then divides into middle and lower lobe bronchi. A blockage of the bronchus intermedius therefore causes simultaneous lower and middle lobe collapse. The left main bronchus divides andgives off the upper lobe bronchus and then continues downwards as the lower lobe bronchus. It is the upper lobe bronchus that gives off the bronchi to the lingula (the tongue shaped middle lobe equivalent abutting onto the left heart border). This means a left upper lobe collapse would look very different to a right upper lobe collapse as effectively a middle lobe is collapsing (lingula). Some general features of a collapse The collapsed lobe becomes denser (more radio-opaque) and smaller. The remaining lung becomes darker (more radio-lucent) as it expands to fill the space lost due to the collapse. If the lobe is big enough (the largest lobes being the lower lobes), you may see crowding of the ribs, a raised hemi-diaphragm and sometimes mediastinal shift to the side of collapse. Left upper lobe collapse The appearance of left upper lobe collapse is often misinterpreted even by fairly senior clinicians. I think this is because it is assumed that it should look like an area of increased density defined by a straight line. 1 As the left upper lobe collapses, it collapses forwards, this results in a lobe that gradually thins out as you move peripherally from the mediastinum (a veil type appearance). There is no sharp line of a horizontal fissure to define it. The delineation of the oblique fissure that defines the area of collapse is only seen on the lateral radiograph. The outline of the left heart is lost as this corresponds to lingula. Usually most of the superior mediastinal outline is also lost as it corresponds to the anterior and apico-posterior segments of the upper lobe. Delineation of the major fissure on the lateral This is called a juxta-phrenic peak it is caused by pleura attached to the diaphragm pulling it upwards due volume loss Occasionally the appearance is further confused by aeration of much of the left superior chest with lung outlining the left superior mediatinum. This is caused by the right upper lobe crossing the midline and filling the space previously occupied by the left upper lobe. 2 Left upper lobe collapse with aeration caused by the Right upper lobe expanding across the midline. Right upper collapse(RUL) RUL collapse is usually much easier to recognize and understand. It is well delineated by the horizontal fissure. The horizontal fissure has been pulled upward due to volume loss and the outline of the right superior mediastinum is lost as it is in contact with the anterior aspect of the upper lobe. RUL collapse less obvious on this AP lordotic view Classic RUL collapse the relative expansion and convexity near the hilum is indicative of tumour (Golden’s S sign) Middle lobe collapse/Consolidation The middle lobe is quite small and you seldom see evidence of volume loss. 3 In this radiograph there is clearly consolidation in the middle lobe although it is not delineated by the horizontal fissure superiorly. Note the loss of the right heart border can also occur with pectus excavatum. The sternal compression means that the heart is rotated to the left. The anterior ribs are sharply angled downwards in a 7 configuration. Left lower lobe collapse This is easy to spot when it is big. It is much more difficult when the lobe has collapsed down into a very small volume. As the lower lobe is a big lobe, evidence of loss of volume may be very useful. Clearly we should be looking for loss of the outline of the descending aorta and loss of the left hemi-diaphragm. The lower lobe collapses essentially cause a 4 triangle behind the heart with its apex at the appropriate hilum as seen on this radiograph. The triangle is formed by the major fissure abutting onto descending aorta (normally in contact with the posterior aspect of the lower lobe) and henidiaphragm (normally in contact with anterobasal segement of lower lobe). The right shoulder is rotated back and hence if the radiograph was normal more mediastinum would be seen on the right. There is crowding of the ribs on the left. There is loss of the outline of the descending aorta and left hemidiapragm. The is a double heart border. The more medial is the outline of the solid lower lobe. This is as classic a left lower lobe collapse. The endotracheal tube is in a satisfactory position and the cardiac monitoring is noted. Subtle LLL collapse. The right shoulder is back and so on the PA radiograph the right side of the chest should be darker,it isn’t. There is very slight crowding of ribs on the left. There is loss of outline of the lower descending aorta and medial aspect of the left hemidiaphragm. Right lower lobe and bronchus intermedius collapse Many causes of collapse are due to tumour and I think that I see as many middle and lower lobe collapses (due to bronchus intermedius obstruction) as I do pure lower lobe collapses (due to lower lobe bronchus obstruction). Apart from the signs of volume loss, we expect to see a sharp boundary superiorly caused by major fissure in lower lobe collapse, and a horizontal and major fissure in middle and lower lobe collapse. If the middle lobe is involved we should lose the outline if the right atrium as well. 5 A B In casebe A, very theredifficult was a tumour bronchus caused It can to tell. of Inthe A there was intermedius a tumour ofthat thehad bronchus middle and lower intermedius that lobe had collapse. resulted in middle and lower lobe collapse. Case B turned to bewas a lower lobe tumour thisno emphysematous patient. In case out B, there a lower lobe tumourin and evidence of middle lobe collapse. It can be very difficult to tell. 6 4 INFECTIONS Lobar pneumonia A lobar pneumonia is what one thinks of as a typical chest infection. It is a process originating in the airspaces and spreads via the pores of Khon. (These are openings in the alveolar wall allowing gas and fluid transfer). This process often produces large areas of consolidation, often lobar in distribution typically with air bronchograms. It is frequently caused by a Strep Pneumonaie infection in a young patient. Lobar pneumonias should not occur in patients beyond their 40s but If they do complete resolution must occur. Some clinicians see it as an indication for a bronchoscopy in this subgroup of patients, as a lobar pneumonia in these patients suggests a bronchial lesion. Apart from strep.pneumoniae , the other organism that classically causes a lobar pneumonia is Klebsiella. This classically causes bulging fissures and is commonly associated with cavitation and commonly occurs in alcoholics. Before discussing broncho pneumonias, we need to revise a liitle anatomy. The secondary pulmonary lobule Each lobe can be divided into broncho-pulmonary segments. These are then divided into secondary pulmonary lobules. These are separated by thin septations which are hardly visible even on high resolution CT. The lymphatics and pulmonary veins travel in these septa. Each lobule has about 10 terminal bronchioles, which leads to smaller units of the lung called acini. 7 acinus Terminal bronchiole and accompanying artery Pulmonary vein and lymphatics in the septa Secondary pulmonary lobule Bronchopneumonia This is caused by consolidation in multiple overlapping secondary pulmonary lobules. The process is thought to be centered on the airways and therefore air bronchograms are much less common. After considering the anatomy of the secondary pulmonary lobules you will understand why some people think of it as a patchwork quilt pattern of shadowing. Probably the archetypal bronchopneumonia occurs with Staphylococcus Aureus which is often bilateral and commonly secondary to influenza. Staphylococcus Aureus is also associated with cavitation. This pattern of disease is usually bacterial. 8 Staph pneumonia p Arrows point to multiple small cavities.P indicates a pneumatocoele Some pneumonias present with a more diffuse pattern of disease and cause either interstitial shadowing and associated ground glass shadowing (alveolar oedema).These tend to be viral pneumonias, pneumocystis or bacterial pneumonias in a immunosuppressed patient (e.g. legionella or pseudomonas). Cavities and Pneumatocoeles Pneumatocoeles occur secondary to bronchiole obstruction (they are much more common in paediatrics). This causes air trapping .Both alveolar and mass effect are also rarely seen. Cavitation on the other hand is a hole secondary to central necrosis. Both however are secondary to infection (mnemonic SHITES). Staphylococcus Haemophilus influenzae Tuberculosis Enteric bacteria Streptocooccus pneumatocoeles and abscesses) (pneumatocoeles) (cavitation) (cavitation) (pneumatocoeles) Other conditions associated with holes in the lungs. 1. Bronchogenic Carcinoma-usually large upper lobe squamous cell tumour caused by central necrosis. 9 2. Infarction (rare due to dual blood supply)-secondary to a large area of infarction, often secondarily infected and in the lower lobes. 3. Metastases-squamous, colonic and sarcomas (cavitating metastases are associated with pneumothoraces) 4. Bronchogenic cysts (rare) 5. Sequestrated lung- (rare) Left lower lobe preponderance. 6. Rheumatoid nodules. These may rarely cavitate. 7. Wegeners Granulomatosis (rare).Multiple lesions associated with patches of haemorrhage and inflammatory change. 8. Sarcoid- Cavitating nodules are rare in sarcoidosis. 9. Bullous disease Lung abscess This abscess was located in the apical segment of the right lower lobe Radiologists by and large are hopeless at guessing the organism. We can usually locate the site of the pathology. We are able to say if the picture is essentially one of a bronchopneumonia, a lobar pneumonia or if it is mainly in the interstitium. Some organisms that are worth knowing about and why Streptococcus Pnemonaie. It is the most prevalent and a cause of broncho and lobar pneumonias in all patients (immunosuppressed or otherwise). Staphylococcus Aureus. It usually presents as a bilateral bronchopneumonia with cavitation and pneumatocoeles (most commonly in children).Commonly post influenza (together with strep pneumonaie and Haemophilus Influenzae). It is 10 importantAlso in drug addicts, the immunosuppressed, those with indwelling catheters and in patients with bacterial endocarditis. It is a relatively common cause of empyemas (walled off pleurally based infection). Haemophilus Influenzae. It causes a bilateral patchy bronchopneumonia and is seen particularly inpatients with COPD. Mycoplasma. It causes A lower lobe patchy/peribronchial consolidation. Frequently, it starts as a lower lobe process associated with ground glass or interstitial shadowing with small irregular nodules. Bilateral involvement is not uncommon and can cause lymphadenopathy in paediatric patients. Pseudomonas. Often seen in a debilitated patient who require mechanical ventilation. It causes a patchy often bilateral bronchopneumonia with nodular infiltrates Legionella. Usually occurs in elderly, male patients and accounts for 3% of pneumonias in the UK. It has a sub lobar, lower lobe distribution and a 30% association with effusions. It often rapidly spreads to other sites within the chest. Cavitation tends only to be a feature in the immunosuppressed patient. Moxarella Cattarrhalis. It usually causes tracheo-bronchitis or a mild pneumonia. Particularly in patients with carcinoma or COPD. It causes lobar or segmental consolidation and in some patients it causes a bi-basal interstitial pattern.. Streptococcus Pyogenes. It is an uncommon infection that looks like a staphylococcal bronchopneumonia. It usually follows viral infections but tends not to cause pneumatocoeles. Brucella. Acquired from farm animals, it can rarely present with consolidation and effusion. Less than 1% of cases. Pneumocystis Carinii(PCP). This commonly occurs in patients with AIDs (usually the CD4 count is less than 200).Classically bilateral ground glass or interstitial shadowing is present (cysts do occur but this is a CT rather than a plain film finding). It also occurs in other immunosuppressed patients. . 11 Bilateral ground glass/airspace shadowing. In itself consistent with any number of diseases processes of alveolar oedema /consolidation.Consistant with mycoplasma,alveolitis etc . This was pneumocystis Chlamydia Pneumonaie. Person to person spread. Often asymptomatic and makes up about 10% of community acquired pneumonia. Usually patchy, and unifocal consolidation. About half have effusions. Chlamydia Psittaci. It occurs in patients exposed to birds (especially parrots). It is Indistinguishable from a bacterial pneumonia. The appearances vary, from patchy consolidation to lobar pneumonia and sometimes bi-basal interstitial infiltrates. It can be associated with lymphadenopathy and radiological features are often slow to clear Coxiella Burnetti. There is a history of contact with farm animals. Causes a rounded or segmental/lobar consolidation in the lower lobes. Varicella. A serious pneumonia in young adults with a 10-20% mortality. Usually presents with bilateral ill defined nodules measuring 5-10mm in diameter. It may leave calcified nodules in the lower zones (chronic venous hypertension in heart failure is another cause). AIDS AND CHEST INFECTIONS They have a higher incidence of bacterial and TB infections. Pneumocystis Carinii pneumonia occurs when the CD4 count drops below 200 or so. The incidence of fungal infections is also higher. TB only presents typically in less than ½ of patients with PCP infection. Anaerobic infections These almost invariably occurs secondary to aspiration. They are spread by the airways to dependant areas and therefore. The right side of the chest is more commonly affected. 12 We usually think of the basal segments of the lower lobes being involved, but these patients are often supine and so we need to think about which regions are supine in a supine position. These are often anaerobic infections and can be associated with cavitation. Posterior (RUL) Apico-posterior (LUL) Apical (RLL) Apical (LLL) Posterior (RLL) Posterior (LLL) Dependant segments in the supine position TUBERCULOSIS This is a relatively common infection with increasing prevalence. Primary TB Primary TB in adults can present with a large pleural effusion. It may however appear as an infective focus anywhere in the lungs with 30% of cases appearing as increased localized nodular shadowing . The classic appearance in a child is that of the primary complex. This consists of a small focus of consolidation (often difficult to see) in the mid or lower zones of the lungs. This focus is associated with lymphadenopathy in the paratracheal or hilar region to give you the primary complex. It is this focus that often heals and forms a calcified granuloma. 90% of cases these become quiescent and10% reactivate. Child with primary TB. There is right paratracheal lymphadenopathy. The primary focus is not seen. The chronic cough which this child developed has resulted in a pneumomediastinum. Secondary (reactivation) TB 13 By far the most common presentation of TB in adults is secondary or reactivation TB. This affects predominantly the upper lobes and apical segments of the lower lobes. What is seen is a combination of cavitation and consolidation in these areas. The normal evolution of these cavities is to start off thick walled. They may expand as they become quiescent but then become thin walled. Lymphadenopathy is also often evident and compression of the bronchi can arise secondary to lymph node enlargement. Endobronchial spread of TB is common. TB may also result in empyemas (infected pleural effusions) which often calcify on healing. Healing in TB is associated with scarring and fibrosis and this is obviously seen primarily in the upper zones. TB is therefore one of the few causes of upper lobe fibrosis. We might as well deal with this differential diagnosis of upper lobe fibrosis now. Secondary TB in the Right upper lobe and apical segment of left lower lobe. Upper lobe fibrosis differential (mnemonic TRASH) 1. TB (common) 2. Radiation (bilateral radiation changes are uncommon) 3. Ankylosing spodylitis (rare) associated with marked kyphosis) 4. Alveolitis, extrinsic allergic (uncommon) associated with mid zone fibrosis rather than upper lobe fibrosis in reality 5. Aspergillous. Broncho-pulmonary (uncommon) 6. Sarcoidosis (relatively common) 7. Histiocytosis X (rare) Classic bilateral upper lobe fibrosis 14 All the other causes of fibrosis cause predominantly increased mid and lower zone fibrosis and hence shadowing. Miliary TB Another form of primary TB that needs discussion is miliary TB. This looks has the appearance of nodular shadowing. The nodules are typically small (3-5mm) and can be ill or well defined and may take up to a month to develop. The nodulation is secondary to blood borne spread of infection to the interstitium of the lungs; these nodules are also present in the meninges, adrenals, kidneys etc. Urgent treatment is required and there is a differential diagnosis to this appearance. A patient with Miliary TB Not obvious until you look hard at the lung parenchyma Miliary shadowing in a patient with COAD 15 Miliary shadowing differentials 1. Other infections-Mycoplasma, Histoplasmosis, candida and atypical infections 2. Sarcoidosis (patient not as unwell as the chest radiograph suggests) 3. Lymphoma 4. Metastatic disease. renal, thyroid, bone sarcomas, prostate, chorioncarcinoma, pancreas and bronchus. 5. Extrinsic allergic alveolitis-fluffy small nodules which represent centri-acinar (centri-lobular) consolidation. 6. Silicosis- evidence of fibrosis and usually there is a clear history of exposure. Atypical Mycobacterium They are usually of low pathogenicity and ubiquitous. M Kansasii is the only atypical mycobacterium that when cultured on its own is likely to be pathogenic. Usually looks like TB. There is a subgroup of elderly females that tend to present with mid and lower zone nodulation associated with bronchiectasis. ASPERGILLOUS INFECTIONS This is as good a place to cover it. It presents in one of three ways:Aspergilloma These are cavities in the lung which are occupied by fungal balls of aspergillous. Any cause of cavity formation can be responsible (all the causes of upper lobe fibrosis and also cavitation within malignancy). The most common cause overall will be old TB. They are often asymptomatic but may present with massive haemoptysis. Bilateral upper lobe fibrosis with bilateral aspergilloma Invasive Aspergillosis 16 This occurs in immunosuppressed patients. They often have one or more rounded areas of consolidation in the lung. On CT these often have a halo of lower attenuation change around them. This is not pathognomonic, but is highly suggestive of the diagnosis. Bronchopulmonary Aspergillosis These patients present with cough and asthma. They have a eosinophilic picture on their blood film. Flitting areas of consolidation are often seen (these represent eosinophilic infiltrates). These areas tend to be segmental and recur over time. Central bronchi become distended (bronchiectasis) with mucous and spores. This occurs mainly in the mid zones and can cause associated fibrosis, collapse and bronchocoeles (occluded bronchi distend due to central occlusion and dilate into dilated cystic areas from collateral aeration. 17 5 HEART FAILURE This is the inability of the heart to maintain a normal output at normal filling pressures. The inability to maintain a sufficient output for the body’s needs is cardiogenic shock. With a PA radiograph and a good inspiratory effort we can make a reasonable attempt at assessing cardiac size. CARDIOTHORACIC RATIO GIVEN BY A+B/C B A C Remember that heart size can be larger in some populations. West Indian males may have a ratio of 0.6 and still be normal. In addition if there is hyperinflation of the lungs, the failing heart may not be enlarged. Also the measurements of A and B may be inaccurate, if there are significant pericardial fat pads being included in the measurements. Note that with an acute myocardial infarction or a dysrhythmia there may be no cardiac enlargement. Other features that may be helpful when looking at the cardiac silhouette are calcification of heart valves (usually mitral and aortic most commonly). Calcification of the left ventricle especially may represent an old area of infarction. A bulge in this area may represent a left ventricular aneurysm. Calcification of the left atrium tends to occur in old rheumatic heart disease. aortic mitral Position of aortic and mitral valves 18 Signs of raised left atrial pressure Upper lobe blood diversion For upper lobe blood diversion to be a useful sign, the film must be an erect film. Conditions that cause fibrosis or emphysema in the lower lobes cause upper lobe blood diversion. In these conditions it does not necessarily mean that there is raised left atrial pressure. In addition upper lobe emphysema (the normal pattern of smokers) emphysema can also prevent upper lobe blood diversion. What you do is eyeball the radiograph. Is the lung phlethoric anyway (Are you seeing lung markings out to the periphery?)? The vessels are also less well defined as their walls are oedematous. Do the upper lobe vessels generally look more prominent then the lower lobe vessels. Theoretically you should measure the diameter of upper and lower zone vessels which are equidistant from the hila point (The hila point is the point where the superior pulmonary artery crosses the main pulmonary artery and is often not well seen) and establish if the upper lobe vessel is of a larger diameter. Finding an inferiorly placed vessel equidistant from the hila point is often very difficult). Look at the blood vessels between the 1st and 2nd ribs anteriorly they should be less than 3mm in diameter. They should certainly be smaller than the accompanying bronchus. Ground glass shadowing and consolidation Look for alveolar oedema or consolidation which is usually symmetrical and dependant and pleural effusions (fluid in the pleural cavity). Note that bilateral consolidation or ground glass consolidation is a non specific sign of oedema and consolidation for whatever cause. 1. 2. 3. 4. 5. 6. 7. 8. 9. 10. Heart failure/fluid overload Inhaled toxins. Smoke and inhaled gases Near Drowning ARDS Cerebral oedema Aspiration and bilateral bronchopneumaonia.-usually unilateral Circulating toxins and drugs reactions. Prolonged dependence on one side Aspiration Rapid expansion of a collapsed lung 19 The meniscus sign of an effusion? A B C A B C The meniscus sign comes about due to the depth of fluid /soft tissue that absorbs x-rays. It has nothing to do with surface tension and does not distinguish fluid from pleural thickening. Clearly the meniscus would change if it was fluid and the patient lay supine or on their side Other general comments about effusions 1. The right hemi-diaphragm is more permeable Therefore ascites is often associated with right sided effusions 2. Liver abscesses cause right sided effusions 3. Sub-phrenic abscesses are often a cause right sided effusions 4. In general it is said that left sided effusions are more worrying and assoc with pericardial disease, thoracic aneurysm, oesophageal rupture, pulmonary embolism and pneumonia.I think this is over emphasized and I have seen several patients with mediastinal bleeds and right sided effusions. 5. Remember in the context of infection an effusion (particularly if bulging) may represent an empyema. Bilateral consolidation secondary to failure. The are of lucency is due to a bulla unmasked by the surrounding consolidation. 20 Lymphatic overload The lymphatics are often working flat out to clear the excess fluid. Look for evidence of lymphatic overload (swollen septa between pulmonary lobules (septal lines/ Kerley B lines). Subpleural fluid also sometimes accumulates. Septal lines/Kerley B lines. Engorged lymphatics which run in the septa. Although they do occur in other conditions (Lymphangitis Carcinomatosa), they usually indicate heart failure/overload. There is also a small subpleural fluid collection. Pericardial Fluid This can result in enlargement of the cardiac silhouette which can be massive. It is important to remember certain points. It is the speed of accumulation of the pericardial fluid rather than quantity that dictates how symptomatic the effusion is. Usually there is a relatively rapid increase in diameter of cardiac contour with no particular pattern of chamber enlargement. A Flask like appearance is typical, sometimes overlying the hila. A lack of pulmonary congestion is also a pointer (restriction of right and left sided cardiac output). There are many cause usually viral (cocsackie in particular), Dressslers syndrome (usually1-2 weeks after MI), uraemia, collagen vascular disease, hypothyroidism, CCF ,and rarely tumour (mesothelioma especially). Aortric dissections involving the arch (and in particular the ascending aorta) can also cause bleeding into the pericardium. 21 Some notes on cardiac enlargement Being able to tell which chamber of the heart is predominantly enlarged from the cardiac contour is less important than ever. This is because echocardiography and now MR have taken over this role. Rather than try and remember each outline associated with defects. Remember what enlargement of different chambers look like and then put it together. Apex turns up with right ventricular enlargement. A child with Tetralogy of Fallot –upturned apex in keeping with Right Ventricular Hyppertrophy The Apex goes down with left ventricular enlargement. Right atrial enlargement causes bulging on the right side. Left atrial enlargement causes enlargement of the atrium behind the heart. The carina is often splayed,a double heart border arises on the right and the left atrial appendage enlarges. In Mitral stenosis, you would expect left atrial enlargement and pulmonary congestion. Left ventricular hypertrophy would occur with mixed mitral valve disease. Left atrial appendage Double heart border Mixed mitral valve disease. Enlarged left atrial appendage and left atrium (splayed carina, Double right heart border). There is left ventricular hypertrophy (apex down secondary to mitral regurgitation. Thus in an ASD, you would expect right atrial and ventricular enlargement.The lungs would be phlethoric. Left ventricular enlargement would only occur with Eisenmengers syndrome(reversal of flow form right to left). In a VSD, you would expect right ventricular enlargement. The lungs would be phlethoric. 22 23