X-ray interpretation is an important part of clinical work for all doctors. Unfortunately it is often an overlooked subject in the medical school curriculum, which many medical students and junior doctors find difficult and daunting. From the same series as The Unofficial Guide to Passing OSCEs, The Unofficial Guide to Radiology aims to remedy this by providing a systematic approach to chest, abdominal and musculoskeletal X-ray interpretation. It is designed to be a useful learning resource for medical students, junior and hospital doctors, nurse practitioners and radiology trainees. The chest, abdominal and musculoskeletal X-ray chapters contain step-by-step approaches to interpreting and presenting X-rays. Each of these chapters then covers 20 common and important X-ray cases/diagnoses, which a junior doctor should be able to confidently identify. The content is in line with the Royal College of Radiologists' Undergraduate Radiology Curriculum 2012, making it up to date and relevant to today's students and junior doctors. The layout is designed to make the book as clinically relevant as possible; the X-rays are presented in the context of a clinical scenario. The reader is asked to "present their findings" before turning over the page to reveal a model X-ray report accompanied by a fully annotated version of the X-ray. This encourages the reader to look at the X-ray thoroughly, as if working on a ward, and come to their own conclusions before seeing the answers. To further enhance the clinical relevance, each case has 5 clinical and radiology-related multiple-choice questions with detailed answers. These are aimed to test core knowledge needed for exams and working life, and illustrate how the X-ray findings will influence patient management. One of the keys to X-ray interpretation is practice, practice and more practice. The bonus X-ray chapter provides over 50 further X - ray cases to help consolidate the reader's knowledge and provide an opportunity to practice the skills they have learnt. In addition to these four core chapters the introductory chapter covers the (very) basic science behind X-rays, the relevant legislation controlling X-rays and tips on how to request radiology examinations. Additionally a chapter is devoted to other important imaging investigations, such as computed tomography (CT), magnetic resonance imaging (MRI) and ultrasound, covering the details of what the examinations involve, their common indications and contraindications and key imaging findings. The Unofficial Guide to Radiology is written by both radiologists and clinicians, and reviewed by a panel of medical students to ensure its relevance.
About the Author
Zeshan Qureshi is a Paediatrician based at Great Ormond Street and the Institute of Child Health. He graduated with distinction from the university of Southampton, and has published and presented research work extensively and internationally in the fields of pharmacology and medical education. Whilst working in Edinburgh he was part of the leadership team developing a near peer teaching programme, where by junior doctors, throughout south east scotland, were both trained to teach, and delivered teaching across every hospital in the area. This book is an extension of this philosophy: that junior doctors and fresh graduates know how to express complex ideas in order for it to be easily understood from a students perspective. That junior doctors can teach, and write in a complimentary way to senior doctors: one that is friendly and fun, easy to read and relevant to both exams, and the day to day to life of junior doctors. Following the success of The Unofficial Guide to Passing OSCEs and the feedback from the students being taught, The Unofficial Guide to Radiology was developed. This book extensively expands on the radiology chapter in The Unofficial Guide to Passing OSCEs, providing a comprehensive learning resource for X-ray interpretation for medical students, junior and hospital doctors and nurse practitioners.
Read an Excerpt
This introduction to the chapter is aimed at providing a systematic framework for approaching chest X-rays. Further details and examples of the specific X-ray findings discussed below are covered more extensively in the example cases later in the chapter and in the bonus X-ray chapter.
In this book we look only at frontal chest X-rays (PA and AP X-rays), as these account for almost all chest X-rays performed. The lateral chest X-ray is not commonly performed and has been largely replaced by CT.
1. Projection (AP/ PA)
The projection of a chest X-ray can affect its appearance and interpretation. Therefore it is important to determine which projection has been used.
The two possible projections for a frontal chest X-ray are the anteroposterior (AP) and the posteroanterior (PA). Somewhere on the X-ray you should see something that indicates whether it is AP or PA.
The PA X-ray provides the best assessment of the thorax but requires the patient to be able to stand (or sit on a stool). This is the standard projection, so if there is no annotation stating otherwise, you can assume the X-ray is PA.
AP X-rays provide a less comprehensive assessment than PA X-rays due to the effects of magnification and the position of the scapulae (figure 1). They are usually only performed for haemodynamically compromised patients.
If you cannot remember which one is the standard view, remember, "AP is 'crAP', so PA is standard".
If you are asked to justify why an X-ray is PA, remember that in PA X-rays, the patient's arms are positioned in such a way that the scapulae are pulled almost fully out of the lung fields. In AP X-rays, this positioning is not possible, and the scapulae are projected further over the lungs.
2. Patient Details
It is important to ensure you are looking at the correct X-ray from the correct patient.
The patient's details will be on the X-ray (unless anonymised for the exam).
Say the name, age/date of birth, and when the X-ray was taken.
The age and gender of the patient are useful for helping to formulate your differential diagnosis.
3. Technical Quality
Check that the X-ray includes all of the thorax (both lung apices, the lateral sides of the ribcage, and both costophrenic angles). Important pathology can be missed if the entire thorax is not imaged.
It is unlikely that you will be given an X-ray in the exam that does not show the entire lungs, but some parts are occasionally missed in practice.
It is important to assess RIP – Rotation, Inspiration, Penetration.
The heads of the clavicles (medial ends) should be equidistant from the spinous processes of the vertebral bodies. If they are not, the patient is rotated.
Patient rotation can erroneously give the impression of mediastinal shift or lung pathology (figure 2).
PA and AP X-rays are taken in held deep inspiration. Count the ribs to assess inspiratory effort.
You should count down to the lowest rib crossing through the diaphragm. Six anterior ribs or 10 posterior ribs indicate adequate inspiratory effort.
Fewer ribs indicate an underinspired X-ray. This may be due to the timing of the X-ray, or, more frequently, because the patient is unable to take and hold a deep breath (due to pain, breathing problems, or confusion). Underinspired X-rays can cause crowding of the lung markings at the bases, incorrectly giving the impression of consolidation or other pathology. Additionally, the heart may appear falsely enlarged (figure 1).
More ribs, particularly with flattened diaphragms, indicate hyperinflation due to airway obstruction, such as chronic obstructive airway disease (COPD).
The X-ray is adequately penetrated if you can just see the vertebral bodies behind the heart.
"Underpenetrated" means that you cannot see behind the heart and "overpenetrated" means that you will be able to see the vertebral bodies very clearly.
Over and under penetration can obscure or obliterate significant findings, particularly in the lungs.
This is less of a problem with the advent of digital viewers which allow the X-ray "windows" to be manipulated. However, this function can only manipulate the image so far, so adequate penetration is still important.
4. Obvious Abnormalities
If you can see obvious abnormalities, say so and describe them:
Which lung is involved?
Which part of the lung?
If possible, say which lobe is/lobes are involved. Remember it is not always possible to determine this on an X-ray – in which case use upper, middle, or lower zone to describe the abnormality's location. CT can locate abnormalities more accurately.
Is it focal or diffuse, rounded or spiculated, well or poorly demarcated?
Describe the density of an abnormality in relation to the normal surrounding tissue, e.g. if the abnormality is in the lung, compare it to the normal lung; if in the bone, compare it with the other bones.
If the abnormality is denser (i.e. whiter) than the normal tissue, you can say that there is increased opacification or density; if less-dense (i.e. blacker), say there is increased lucency or reduced density.
You should assess whether the abnormality has a uniform or heterogenous appearance.
If there is anything else in the abnormality, such as air bronchograms or fluid levels, then mention these as well.
Are there other abnormalities, such as volume change, bony abnormalities, or surgical clips?
5. Systematic Review of the X-ray (Figure 3)
Initially assess from a distance to see differences in lung shadowing/obvious masses. Previously, when using hard-copy X-rays, you would be taught to look at the X-ray initially from four feet; however, now most X-rays are viewed on computer so make sure you zoom out as much as possible for your initial inspection.
After that, reassess from close-up to look for subtle abnormalities.
It does not matter what system you use for assessing the X-ray, as long as you do not miss any areas.
A useful system is ABCDD (Airway, Breathing, Circulation, Diaphragm/ Delicates).
Also comment on manmade abnormalities, e.g. lines, pacemakers, a nasogastric (NG) tube.
A – Airway
Is the trachea central?
If not, is it deviated due to patient rotation or pathology?
If the cause is pathological, is the trachea being pulled to one side (volume loss, such as lobar or lung collapse) or pushed away (increased volume such as a large pleural effusion or mediastinal mass)?
B – Breathing
Start in the apices and work down to the costophrenic angles, comparing both lungs to look for differences.
Ensure that you inspect the entire lung, including the apices, hila, and costophrenic angles.
The left hilum should never be lower than the right. If this is the case, you must look for volume loss either pulling the right hilum up or pulling the left hilum down.
Both hila should be the same density and have no lumps or convex margins.
Look around the edge of the lungs, assessing for pneumothoraces. These can be particularly subtle at the lung apex.
C – Cardiac and mediastinum
Assess the heart size. Cardiomegaly is defined by the maximal transverse cardiac diameter being greater than 50% of the maximal transverse internal thoracic diameter (cardiothoracic ratio). This can only be accurately assessed on a well-inspired PA X-ray due the effects of magnification on AP and underinspired X-rays (see figure 1). However, it is still important to assess cardiac size on an AP X-ray – if it's normal on the AP, then it will be normal on the PA; conversely, if it is grossly enlarged on the AP, it is likely to be enlarged on the PA X-ray.
The cardiac and mediastinal borders should be clearly visible. If this is not the case, you must consider whether there is pathology in the adjacent lung.
The mediastinum and heart should be positioned over the thoracic vertebra. If this is not the case, you must first check that the patient is not rotated. Then you must assess for volume change in the lungs (either volume loss pulling structures towards the abnormal side or increased volume pushing them away), accounting for the position of the mediastinum and heart. Marginal mediastinal shift can be observed if the margins of the thoracic vertebral bodies can be clearly seen beyond the cardiac and mediastinal contours on a well-centred X-ray.
Widening of the mediastinum may be due to technical factors (e.g. AP projection), vascular structures (e.g. unfolding of the thoracic aorta or aortic dissection), masses (mediastinal tumours or lymph node enlargement) or haemorrhage (e.g. ruptured aorta). The clinical findings in such cases are important, as the cause can be difficult to determine on X-ray. CT can be used if required for further assessment.
The right paratracheal stripe can be useful to assess, if visible. It is composed of the soft tissue between the medial wall of the right lung and the right wall of the trachea. It is visible in 50-60% of X-rays and should measure <5mm in diameter. If it is thickened, it is commonly due to lymph node enlargement.
The aortopulmonary window is another area to assess for lymph node enlargement. The aortopulmonary window is located between the aortic arch and the left pulmonary artery. Normally there should be no soft tissue visible in this region, thus giving the impression of a window. If this is not the case, you must consider lymph node enlargement.
You should assess the mediastinum for the presence of gas within it (pneumomediastinum). This appears as linear lucencies projected over the mediastinum. These often extend into the neck and may be associated with surgical emphysema (figure 4).
It is important to remember that the lung continues behind the heart (a large portion of the left lower lobe is behind the heart). The cardiac shadow should be of uniform density. If this is not the case, you must consider whether retrocardiac pathology, such as consolidation, lobar collapse, or a mass, is present. This can be difficult to assess due to the overlying cardiac shadow. Inverting the image often makes any abnormality more obvious (figure 5).
D – Diaphragm
Both hemidiaphragms should be visible and upwardly convex. Flattening of a hemidiaphragm suggests raised intrathoracic pressure either from lung hyperexpansion, as seen in air trapping with COPD, or tension pneumothoraces.
The right hemidiaphragm is normally slightly higher than the left due to the mass effect of the adjacent liver. If this is not the case, you must consider whether one of the hemidiaphragms is is being abnormally pulled up or pushed down.
Remember that the lungs extend behind the diaphragms, so you need to look for lung pathology through the hemidiaphragms. Again, inverting the image can make such pathology more obvious.
Look for free air under the diaphragm. This can be difficult, as the gastric bubble and bowel loops can have a similar appearance (figure 6).
The costophrenic angles should be sharp. If not, there is likely to be pleural fluid present.
D – Delicates
Assess the bones. Look at the ribs for fractures or bone destruction. Assess the rib spaces, which should be roughly equal. Narrowing can be seen with volume loss in the underlying lung. Review the rest of the imaged skeleton for fractures or destructive bone lesions.
Look at the soft tissues for evidence of surgical emphysema (gas [black areas] in the soft tissues) and previous surgery (surgical clips, mastectomy).
Lines(see Figure 7)
An endotracheal (ET) tube should have its tip proximal to the carina. Problems can arise if it is inserted too far and the tip enters one of the bronchi. This will result in collapse of the non-ventilated lobes.
The tip of a nasogastric (NG) tube should lie well below the left hemidiaphragm in the stomach. Problems to look out for include misplacement into the lungs, and the tip being within the distal oesophagus.
Central lines are most commonly inserted into the internal jugular veins. Their tips should be in mid or lower superior vena cava. Complications include misplacement and a pneumothorax.
6. Review Areas
Double-check the following areas, since pathology is easily overlooked at these sites on initial viewing (see figure 8):
Behind the heart
Under the diaphragm
Summarise your findings and give a differential list. Think about the history and clinical examination as well as the X-ray findings when making your differential diagnosis.
Say whether you would like to review previous imaging if you think this would help.
Suggest further investigations, including imaging, which may be useful.
Suggest a management plan for the patient.
SPECIFIC FINDINGS ON CHEST X-RAY
Dense or patchy consolidation, usually unilateral.
May contain air bronchograms (air containing bronchioles running through consolidated lung).
In the lower zones, pneumonia may be difficult to distinguish from effusions, so both should be on your differential list (remember there is often a parapneumonic effusion).
The silhouette sign is useful for locating in which lobe of the lung the pathology is located (figure 9). Normally, there is a sharp border between the aerated lung and the soft tissues of the heart and diaphragm. This is due to the large differences in the number of X-rays attenuated by the soft tissues (a relatively high proportion of X-rays) and the lung (relatively few X-rays).
If there is consolidation, the normally aerated lung is replaced by fluid or pus. This attenuates X-rays to a similar extent to the heart and diaphragms. The usually sharp border between the lung and these structures is thus lost if there is consolidation in the lobe abutting these soft tissues.
It is necessary to know which lobes contact the heart and diaphragmatic borders in order to be able to use the silhouette sign:
* Diaphragms: left and right lower lobes
* Right heart border: right middle lobe
* Left heart border: lingula (part of the left upper lobe)
Remember that pathology can affect more than one lobe.
It is not always possible to identify in which lobe pathology is located. In these cases, describe it as affecting the 'upper, middle, or lower zone'.
Look for blunting of the costophrenic angles, a homogenous opacification, and a fluid level manifesting as a meniscus (figure 10).
ABCDEF can be used as an aide-mémoir for the features of pulmonary oedema (figure 11). Usually only some of these X-ray signs are present, and the diagnosis is made in conjunction with the clinical picture:
A: Alveolar and interstitial shadowing
B: Kerley Blines (little white horizontal lines usually in the lateral lower edges)
C: Cardiomegaly (Cardiothoracic ratio of greater than 50% on a PA X-ray)
D: Upper lobe venous blood Diversion (prominent upper lobe vasculature relative to the lower zones)
F: Fluid in the horizontal fissure
Air within the pleural space (figure 12).
Loss of lung markings in the peripheral lung field. You may also identify a discrete lung edge.
With a simple pneumothorax, there is no mediastinal shift. In contrast, if there is a tension pneumothorax, there may be tracheal/mediastinal deviation away from the pneumothorax, and flattening of the ipsilateral dome of the diaphragm. A tension pneumothorax should never be diagnosed by a chest X-ray! It is a medical emergency, and is diagnosed clinically and treated immediately with needle thoracocentesis.
Lobar Collapse(Figure 13)
Look for loss of volume
* A raised hemidiaphragm ipsilaterally
* Tracheal and mediastinal shift towards the collapsed side
* Displacement of the hila
* Narrowing of the space between the ribs compared to the opposite side
Left Upper Lobe (LUL): Veil sign – the whole lung field looks like it's covered by a veil. This can be difficult to appreciate. Luftsichel sign is sometimes seen – radiolucency in the left upper zone, around the aortic arch, due to compensatory hyperinflation of the left lower lobe.
Left Lower Lobe (LLL): Sail sign – sharp line like the edge of a sail at the same angle as the left heart border – giving the impression of a double left heart border. The medial part of the left hemidiaphragm will be indistinct, but the left heart border clear.(Continues…)
Excerpted from "The Unofficial Guide to Radiology"
Copyright © 2014 Zeshan Oureshi.
Excerpted by permission of Zeshan Qureshi.
All rights reserved. No part of this excerpt may be reproduced or reprinted without permission in writing from the publisher.
Excerpts are provided by Dial-A-Book Inc. solely for the personal use of visitors to this web site.
Table of Contents
Chest X-Rays, 17,
Abdominal X-Rays, 181,
Orthopaedic X-Rays, 335,
CT Scans, 521,
MRI Scans, 543,
Ultrasound Scan, 557,
Nuclear Medicine Scans, 565,
Bonus Cases, 579,
Bonus Chest X-Rays, 579,
Advanced Chest X-Rays, 603,
Bonus Abdominal X-Rays, 613,
Advanced Abdominal X-Rays, 625,
Bonus Orthopaedic X-Rays, 637,
Advanced Orthopaedic X-Rays, 671,