ofemergency radiology chest radiographs-ii

ABC of Emergency Radiology

CHEST RADIOGRAPHS-II

D W Hodgkinson, B R O'Driscoll, P A Driscoll, D A Nicholson

The common conditions seen in the accident and emergency departmentthat require chest radiography can be divided into two types-those resultingfrom trauma and those from other causes.

TraumaInjuries associated with blunt thoracic trauma

Possible associatedMechanism Chest wall injury intrathoracic injury

Low energy transfer Unilateral rib fracture Pulmonary(direct blow) Anterior sternal fracture contusion

Cardiac contusionHigh energy transfer Chest wall may be intact Ruptured aorta

(deceleration) Cardiac contusionBilateral rib fracture Ruptured

diaphragmSternal fracture Ruptured bronchus

Crush injury Bilateral rib fractures with or Ruptured bronchuswithout flail chest Cardiac contusion

Ipsilateral rib fractures with or Pulmonarywithout flail chest contusion

Possible contralateralinternal rib fracture

There are three main mechanisms of chesttrauma: low energy transfer (low velocityimpact-for example, a kick), high energytransfer (high velocity impact-for example, aroad traffic accident), and crush injury.

Ribfractures are best diagnosed clinically andare more common in high energy transfer andcrush injuries. Remember the chest film isrequested to investigate the presence or absenceof associated intrathoracic injuries.

Flail segment-This occurs when two or moreribs are fractured in two or more places or whenthe clavicle and first rib are similarly affected. It isassociated with serious intrathoracic injury,especially pulmonary contusion, and mayprogress to respiratory failure.

FIG i-Anteroposterior radiograph showing rightintercostal drain, pneumomediastinum, and severesurgical emphysema (linear lucent lines in the rightpectoral sheath overlying the right hemithorax andin the softtissues). Rib fractures are seen in the enlargeddetail.

Aortic dissection-Ten per cent ofpatients with this condition survive toreach hospital. They must be identified as soon as possible since a successfuloutcome depends on immediate identification and treatment. The diagnosisrests on a strong clinical suspicion, plain radiographic features, andultimately arteriography.

Cardiac contusion is associated with crush and high energy transferinjuries. The chest radiograph may appear normal but there is usuallyevidence of disruption ofthe thoracic wall with or without pulmonarycontusion.

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Signs of dissecting thoracic aortaWidening of the superior mediastinum to>8cmDepression of the left main bronchus to anangle < 400 with the tracheaTracheal shift to the rightBlurring of the aortic outlineObliteration of the medial aspect to the leftupper lobe (pleural capping)Opacification of the angle between the aortaand the left pulmonary arteryLateral displacement of nasogastric tube inoesophagus

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Pulmonary contusion-Patchy consolidation is the early radiographicfeature of this condition but this may underestimate the severity of theinjury.

Ruptured major airway-This should be suspected in the presence of anyof the following: pneumomediastinum, surgical emphysema in the neck,haemoptysis, collapse of a lung or lobe, pneumothorax with major air leak.

Ruptured diaphragm-This is more common on the left and should besuspected when there is a history of high energy transfer or crush injurywith a bowel or stomach shadow in the thoracic cavity or an ill definedhemidiaphragm.

Penetrating chest trauma-The plain posteroanterior chest radiograph isthe most important investigation. Most penetrating wounds damage onlythe chest wall and underlying lung. Even the more serious injuries-forexample, cardiac tamponade, transected aorta, lacerated diaphragm, andmajor airway injury-can be diagnosed by the mechanism of injury, theclinical findings, and a posteroanterior or anteroposterior chest radiograph.Remember that penetrating injuries to the neck and abdomen can affect thecontents of the thoracic cavity. More specifically, globular enlargement ofthe cardiac silhouette may not be apparent in the plain film even in thepresence of life threatening cardiac tamponade.

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.... ...................... ......FIG 2-Small pneumoperitoneum caused by a stabwound to the left lower chest (arrow).

Non-trauma

When spontaneous thoracic aortic dissectionis clinically suspected the patient should befurther investigated by computedtomography or angiography

Chest painA chest radiograph is not usually indicated in the early management of

acute myocardial infarction and angina unless the diagnosis is in doubt. Apatient with spontaneous thoracic aortic dissection may present with chestpain suggestive of acute myocardial infarction-a chest film may help but itis important to be aware of the pitfalls of interpreting an anteroposteriorfilm. Occasionally the posteroanterior or the anteroposterior chest film, orboth, may show clinically silent pulmonary oedema in patients with acutemyocardial infarction.

olus Patients with severe acute central chest pain31 after vomiting who have a pneumomediastinum

or increasing left sided pleural effusion onradiography may have a ruptured oesophagus. Inacute pulmonary embolus the posteroanterior

,ed vessels distal to chest radiograph can show a variety ofabnormalities but more commonly it appearsnormal. The combination of a breathless patient

aryvessels with or without chest pain and a normal

posteroanterior chest radiograph does notexclude a pulmonary embolus. A common

on of lung finding in a chest film is a hiatus hernia; this is notusually the cause of the patient's pain.


Causes of pneumomediastinum orsurgical emphysemaAsthmaRuptured oesophagusPenetrating traumaRuptured bronchus

Radiological changes in pulmonary embiIn many cases the chest radiograph appears norma

Early features which are occasionally seen:Raised hemidiaphragmAbnormally increased radiolucency due to reducembolusAsymmetry of vessels compared with normal sicAbrupt cut off or "rat tail" appearance of pulmon

Late features (commoner than early features):Pleural effusionLinear or wedge shaped shadows due to infarcticOccasionally infarcts may cavitate

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FIG 3-Right middle lobe pneumonia with a silhouette signreducing the definition of the right heart border. There is slightvolume loss in the middle lobe.

FIG 4-Consolidation in the left upper and mid-zoneswith cavitation in a patient with pulmonarytuberculosis.

.. .. . _. ..fB:f

FIG 5--Left upper lobe collapse with the radiologicalsigns of volume loss (raised left hemidiaphragm andraised left hilum) and lossof definition ofthesuperiormediastinum on the left side.

Chest infectionsThe chest radiograph can confirm a clinical diagnosis of pneumonia or

pleural effusion. The film usually appears normal in patients with acuteasthma or exacerbated chronic obstructive pulmonary disease, but it isrequired to exclude conditions implicated in their aetiology orcomplications which will affect the patient's management-for example,pneumonic consolidation, pneumomediastinum, or pneumothorax. Achest radiograph is vital when an immunocompromised patient is thoughtto have an infection.

Unexplained breathlessnessLook for a pneumothorax, evidence of heart failure, or unsuspected

collapse oflobes or segments (figs 5 and 6). Ifthe radiograph appears normalremember the possibility of neuromuscular disorders, pulmonaryembolism, anaemia, central airway lesions (including radiolucent foreignbodies), and the hyperventilation syndrome.

Heart failureThe chest radiograph will usually confirm clinical suspicion of heart

failure or show its severity. Radiological signs of heart failure precedeclinical signs (fig 7).

HaemoptysisLook for evidence of lung cancer or tuberculosis (fig 4). A large tumour

of the trachea or main bronchus may produce no radiological change until a

lung suddenly collapses. Listen for stridor or monophonic wheeze. Don'tforget pulmonary embolism.


Radiological features of pulmonaryoedemaEarly (pulmonary capillary wedge pressureG 18-22 mm Hg)Upper lobe blood diversionPerihilar hazePeribronchial cuffingVague increased density over lower lungfields

Late (pulmonary capillary wedge pressure>25 mm Hg)Kerley's A and B linesExtensive perihilar "bat'swing" shadowingFluid passes into alveolar spacesproducing diffuse poorly defined bilateralbasal infiltrates

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FIG 6-Abnormality in the transradiancy of the left lungfield with a large irregular opacification in the left mid-zone. In this case it represented a pulmonary embolus.

FIG --Large pneumoperitoneum with air under bothdiaphragms.

FIG 7-Cardiomegaly with severe pulmonary oedema.Peribronchial cuffing, well defined Kerley's B lines in the rightlower zone, and bilateral alveolar shadowing are visible.Hyperinflation suggests pre-existing chronic obstructivepulmonary disease.

Abdominal painTry to get an erect posteroanterior or

anteroposterior chest film to look for free gas

below the diaphragm (fig 8). Remember thatcases of lower lobe pneumonia may present withabdominal pain.

Neurological presentations and coma

Remember that any patient with dysphagia or a

poor gag reflex is at risk of developing aspirationpneumonia. This is particularly relevant inunconscious patients. Initially there may be fewradiological signs because aspiration pneumoniatakes time to develop. This condition mostcommonly affects the right middle lobe.

Inhaled foreign bodyMetallic or bony foreign bodies may be seen in

the routine radiograph. The lateral radiographwill show whether a coin is in the oesophagus or

in the trachea. Inhaled organic material such as

food is usually radiolucent, but a lobe or segmentmay have collapsed if the inhalation occurredsome time previously. In acute aspiration air maybe trapped in the affected lobe or segment, whichmay show up as hyperinflation with mediastinalshift to the normal side on the expiration film.

Useful radiological rules and signs

The silhouette signInterfaces between lung and soft tissue structures will have clear margins

on a chest radiograph provided that the interfaces are smooth and tangentialto the x ray beam. If air in the lung at the interface is removed (for example,consolidation) the radiographic boundary will disappear (fig 3). This isknown as the silhouette sign and it can be used to localise and identify bothnormal and abnormal structures.

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Pulmonary oedemaThe radiographic changes are often worsethan the clinical condition of the patient asfluid initially collects in the interstitium

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FIG9Leftsided pleural effusion, a large mass lesion...projectedoverthe aortic knuckle, and a left mastectomy. This

... ...represents~~~~~~~~~~~~~~~~~~~~~~...metataticacioa.f.h. beat

Signs of consolidation(1) Shadowing with ill defined margins due to

piecemeal alveolar involvement. If the processcomes up against a pleural surface the marginmay be clearly defined (as in lobar pneumonia).

(2) No volume loss.(3) Air bronchogram: normally

intrapulmonary airways are invisible unless "endon" to the x ray beam, but if they pass through azone of consolidation they become visible.

(4) Vascular changes: blood vessels arenormally seen because their soft tissue densitycontrasts against air-containing lung but withconsolidation they become obscured.

Signs of pleural effusionThese signs are different in the erect and

supine films.Erect film-Homogenous opacification of the

chest; obliteration of the costophrenic angle andthe hemidiaphragm; the upper margin is concaveto the lung and is higher laterally.

Supine film-Reduced transradiancy of thehemithorax due to dorsal pooling. The abovesigns are often absent.

SummaryName, age, and datePosition of any invasive equipmentMediastinum, including hila and size andshape of heartDiaphragms, including costophrenic anglesLung field abnormalities, including apicesBonesExtrathoracic soft tissues

Signs of lobar collapse(1) Crowding of vessels and airways within the lobe.(2) Raised hemidiaphragm.(3) Shift of mediastinum, hilum, fissures, and other structures.(4) Compensatory hyperinflation.(5) Ribs close together.

D W Hodgkinson is senior registrar in emergency medicine, B R O'Driscoll is consultant inrespiratory medicine, P A Driscoll is senior lecturer in emergency medicine, and D A Nicholsonis consultant radiologist, Hope Hospital, Salford.The ABC of Emergency Radiology has been edited by David Nicholson and Peter Driscoll.

ANY QUESTIONS

Can men who have had a vasectomy develop epididymitis?

The simple answer is yes. The exact route by whichinfective organisms gain access to the epididymis is notclear. As long ago as 1953 it was suggested that reflux ofurine from a full bladder could occur through the normalejaculatory duct check valve on the floor of the prostaticurethra, allowing infected urine to pass along the lumen ofthe vas deferens to the epididymis.1 Such vasoepididymalreflux, however, has never been documented undernormal conditions. It can occur after prostatectomy whenthe ejaculatory duct check valve has been damaged andurine has been reported to leak from the cut end of thevas.' Prophylactic vasoligation during prostatectomy,however, is no longer performed routinely, and epi-didymitis after prostatectomy has become a rare event,largely because of improved sterilisation of endoscopicinstruments and treatment of known urinary infectionbefore operation.Under normal conditions vasoepididymal reflux cannot

be shown even under the provocation of lifting a heavyweight with a full bladder. Direct endoscopic injection offluid into the ejaculatory duct rarely produces reflux ofurine, and, even under very high pressure, flow cannot be

achieved beyond the junction of the vas deferens with theduct of the epididymis.3 The presence of secretions andproducts of spermatogenesis, together with peristalticactivity down the vas deferens towards the seminal vesicle,may also act as a physical barrier to intraluminal trans-mission of infection.

It seems most likely, therefore, that infection reachesthe epididymis via the lymphatics and lymphatic spaceswhich follow the vasal arteries; hence occlusion of the vasdeferens does not protect against epididymitis.For reasons which are not entirely clear, epididymitis

after vasectomy can be notoriously difficult to treat, andprolonged courses of broad spectrum antibiotics may benecessary to obtain complete resolution. In some patients,despite adequate treatment, inflammation and epididymalpain may persist, probably because of rupture of epi-didymal tubules and leakage of sperm with infectiveorganisms into the epididymis to form small, chronicallyinfected sperm granulomas.-NIGEL BULLOCK, consultanturologist, CambridgeI Badenoch AW. Vaso-epididymal reflux syndrome. Proc R Soc Med

1953;46:847-9.2 Hanley HG. Urinary fistula following scrotal vasectomy. Br J Urol

1945;17:34-5.3 Wolin LH. On the aetiology ofepididymitis. Bry Urol 1971;105:531-3.

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