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The aim of this five part series is to

give you a basic system for lookingat chestx ray films. They shouldenable you to say something sensible

when presented with a film in your finalsand be confident that you are not missingserious disease when you view a film onyour own as a house officer.

Looking at chest x ray filmsthe

system

By the time you do finals you will havelearnt a system for examining theabdomen; you also need to develop a sys-tem for looking atxray films. This will

reduce your chances of missing abnor-malities and it will provide a structuredpatter to come out with in exams whenyou are under pressure.

Lets start by looking at a normal chestxray film (fig 1). Use this film as a refer-ence point during the rest of the article.

Firstly, some technical details: Quicklylook at the film to get some useful infor-mation about the patient:

Male or female? Look for thepresence of breast shadows (this will

help you to notice a mastectomytoo). Old or young? Try to use the patients

age to your advantage by makingsensible suggestions. A 20 year old ismuch less likely to have malignancythan someone who is 70.

Good inspiration? Its easy to get tiedup in knots over thisand sometimesnot get any further. The diaphragmsshould lie at the level of the sixth ribsanteriorly. The right hemidiaphragmis usually higher than the left becausethe liver pushes it up.

Good penetration? You should justbe able to see the lower thoracicvertebral bodies through the heart.

Is the patient rotated? The spinousprocesses of the thoracic vertebraeshould be midway between themedial ends of the clavicles.

Most chestxray films are takenposterior anterior (PA)that is, thexrays shoot through from the backof the patient to the xray plate infront of the patient. If the patient istoo sick to stand up for this, an

anterior posterior (AP) film will bedonethat is, the xrays shootthrough from front to back. Ananterior posterior film will always

be labelled as AP, so if nothing is

written on the fi lm it is safe toassume it is PA. PA films are better,particularly because the heart is notas magnified as on an AP film,making it easier to comment on theheart size. Tip: You can avoid the

whole PA/AP debate by describingall chestxray films frontalthatis, you are looking at the patient

straight on. Finally, some examiners like you to

call xray films radiographs; strictlyspeaking you cant actually see thexrays themselves.

You can summarise all the above infor-mation in a simple opening phrase:This is a frontal chest radiograph of ayoung male patient. The patient has takena good inspiration and is not rotated; thefilm is well penetrated.

While you are saying this keep lookingat the film. First look at the mediastinal

contoursrun your eye down the leftside of the patient and then up theright.

The trachea should be central. Theaortic arch is the first structure on

Chest x rays made easyIn the first of a five part series, Elizabeth Dicktakes you through a normal chest x ray

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Fig 1 Normal chest x ray film

Superior vena cava

Right hilum andright main bronchus

Right atrium

Cardio-phrenic angle

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Trachea

Aortic arch

Left hilum

Pulmonary arterybranches fan out

Left atrium

Lung peripheries

Left ventricle

Costophrenic angle

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the left, followed by the leftpulmonary artery; notice how youcan trace the pulmonary artery

branches fanning out through thelung (see fig 1).

Two thirds of the heart lies on the left

side of the chest, with one third onthe right. The heart should take upno more than half of the thoraciccavity. The left border of the heart ismade up by the left atrium and left

ventricle. The right border is made up by the

right atrium alone (the right ventriclesits anteriorly and therefore does nothave a border on the PA chestxrayfilma question that examiners loveto ask. Above the right heart borderlies the edge of the superior venacava.

The pulmonary arteries and mainbronchi arise at the left and righthila. Enlarged lymph nodes canalso occur here, as can primarytumours. These make the hilumseem bulkynote the normal size ofthe hila on this film.

Now look at the lungs. Apart fromthe pulmonary vessels (arteries and

veins ), they should be black(because they are full of air). Scan

both lungs, starting at the apicesand working down, comparing left

with r ight at the same level , just asyou would when listening to thechest with your stethoscope. Thelungs extend behind the heart, solook here too. Force your eye tolook at the periphery of the lungsyou should not see many lungmarkings here; if you do then there

may be disease of the air spaces orinterstitium. Dont forget to lookfor a pneumothoraxin which caseyou would see the sharp line of the

edge of the lung. Make sure you can see the surface of

the hemidiaphragms curvingdownwards, and that thecostophrenic and cardiophrenicangles are not bluntedsuggesting aneffusion. Check there is no free airunder the hemidiaphragm.

Finally look at the soft tissues andbones . Are both breast shadowspresent? Is there a rib fracture? This

would make you look even harderfor a pneumothorax. Are the bonesdestroyed or sclerotic? (see fig 2)

You can summarise your findings as youare looking: The trachea is central, themediastinum is not displaced. The medi-astinal contours and hila seem normal.

The lungs seem clear, with no pneumo-thorax. There is no free air under thediaphragm. The bones and soft tissuesseem normal.

If you have not seen any abnormality bythis point, say soI have not yet identifiedan abnormality so I will now look throughmy review areasand then look at thereview areasplaces where you can

easily miss disease. These are:apices, periphery of the lungs, underand behind the hemidiaphragms(dont forget the lungs will extendhere), and behind the heart.

By the time you have gone throughthe above, showing that you are lookingat the film in a logical fashion, theexaminer should guide you towards the

abnormality.You may be shown a lateral chestx ray (see fig 3), usually to confirm adiagnosis you have made on the PAfilm. Therefore dont panic when thelateral goes up because it means youveprobably made the diagnosis. There areonly two spaces to look at on the later-al film.

The heart lies antero-inferiorly. Lookat the area anterior and superior to theheart. This should be black, because itcontains aerated lung. Similarly the areaposterior to the heart should be black

right down to the hemidiaphragms. Theblackness in these two areas should beequivalent; therefore you can compareone with the other. If the area anteriorand superior to the heart is opacified,suspect disease in the anterior medi-astinum or upper lobes. If the area pos-terior to the heart is opacified suspectcollapse or consolidation in the lowerlobes.

Elizabeth Dickspecialist registrar in radiology North

Thames Deanery

Acknowledgements: I would like to thank Dr Anju Sahdev,Dr Brian Holloway, and Dr Robert Dick for contributing

some of the films shown. Many thanks to Dr Diana

Fairclough, Dr Robert Dick, and Dr Alex Leff for their help-

ful comments reviewing these articles.

Fig 2 Scleroticwhite metastasis in the right seventh rib

Fig 3 Lateral chest x ray (normal)

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