lungexpansioninthediagnosis oflungdisease ·...

he radiographic opacity of normal lungs isthe result of a balance between air-filledspaces and pulmonary blood vessels. Other

lung structures (e.g., bronchial walls, interstitium)are generally too small to be seen when normal.During disease, the opacity of the lungs is fre-quently altered. Therefore, it is important to beable to recognize the normal opacity of the lungs

because abnormal opacity is asign of lung disease. In veteri-nary medicine, most pul-monary diseases produce anincreased opacity of the lungs(i.e., they appear more white),which is a significant finding

but often is not specific for the cause of pul-monary disease. More specific tests for pul-monary disease rely on recognizing patterns ofincreased opacity and other radiographic signs.One of the most important signs, in combinationwith altered opacity, is the size of the affectedlung.When a lung lobe is normal or increased insize, it is described as expanded. Infiltrated andconsolidated are other terms that are used todescribe this appearance. When the lung lobe isdecreased in size, it is described as incompletelyexpanded. The terms collapsed and atelectatic arealso used to describe this appearance.Although commonly used in veterinary medi-cine, these other terms are sometimes controver-

September 2008 479 COMPENDIUM

Lung Expansion in the Diagnosisof Lung DiseaseKevin Winegardner, DVMPeter V. Scrivani, DVMRobin D.Gleed, BVSc,MRCVSCornell UniversityIthaca, New York

T

ABSTRACT:The most common abnormality detected during thoracic radiography of patients with

lung disease is increased opacity of the lungs.Although sensitive for lung disease, this finding alone

is not specific for the cause of lung disease. Other conditions that increase lung opacity include

technical complications and extrapulmonary lesions that compress the lung.Therefore, other

radiographic signs are used to make a more definitive diagnosis.The size of the abnormally opaque

lung lobe can be helpful in differentiating lung disease from other conditions. If the lung is normal to

large in size, it is considered expanded.This situation always indicates disease. If the lung is small, it is

considered incompletely expanded. This finding indicates pulmonary, thoracic wall, or pleural space

disease or a technical complication. Common terms that are used to describe the volume of

expanded or incompletely expanded lungs include infiltration, consolidation, collapse, and atelectasis.

Although they are used as radiographic diagnoses, these terms should not be considered an end-

point analysis, and other radiographic signs must be sought to make a more definitive diagnosis.

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Lung Expansion in the Diagnosis of Lung Disease480

Figure 1. Interstitial versus alveolar pattern.

An example of a diffuse interstitial pattern, also called adiffuse air-space pattern, in a lateral thoracic radiographfrom a geriatric cat with tachypnea. In the lungs, there is amoderate, diffuse increase in soft tissue opacity thatpartially silhouettes with pulmonary blood vessel margins.The differential diagnosis for this lesion is broad; in thiscase, the lung pattern was due to left congestive cardiacfailure secondary to hypertrophic cardiomyopathy.

An example of a diffuse alveolar pattern, also called a diffuse air-spacepattern, in a lateral thoracic radiograph from a middle-aged cat withsevere respiratory distress. In the lungs, there is a severe, diffuse increasein soft tissue opacity that is worse centrally, completely obscurespulmonary blood vessel margins and adjacent heart margins, and createsair bronchograms.The differential diagnosis for this lesion distribution isalso broad; however, the lung pattern in this case was also due to leftcongestive cardiac failure secondary to hypertrophic cardiomyopathy.

sial because they may be mistakenly used as an end-pointanalysis that does not sufficiently describe all the availableradiographic information. Rather, they should be consid-ered radiographic diagnoses that prompt the clinician tomake a differential diagnosis. Therefore, we emphasizethat differentiating whether the lung is expanded is onlyone step in the overall process of making a radiographicdiagnosis.We also emphasize the need to understand theterminology used.

TERMINOLOGY AND DEFINITIONSInfiltration is the migration of gas, fluid, or cells into asubstance, cell, or tissue.1,2 Examples include deep softtissue emphysema secondary to a tracheal tear and theaccumulation of white blood cells in the prostate inresponse to infection. Consolidation can be consideredsolidification of tissue and is applied especially to inflam-matory induration of a normally aerated lung by cellularexudates in the pulmonary alveoli; this process occurs inpneumonia, lung infarct, neoplastic infiltration, and otherconditions.1–4 Both terms are used to describe the patho-logic process that is suspected to be present when a lungof normal or increased size has increased radiographicopacity. Atelectasis is a decrease in, or complete loss of, airin the lung with resultant decreased volume of the ini-tially expanded lung.1–4 The terms atelectasis and collapseare used synonymously and often according to personal

preference; we use atelectasis in this article. When aneonate lung that never fully expanded is described, theterm anectasis (also called primary atelectasis) is used.Thissituation is considered separate from atelectasis becauseit indicates that the lung never expanded after birth, notthat it expanded and subsequently collapsed.1–3The term unstructured interstitial pattern has been usedto describe lungs that have increased opacity withoutcomplete effacement of pulmonary blood vessel margins.Unstructured interstitial pattern has also been used todescribe lungs that are reduced in size (i.e., atelectatic)due to incomplete inhalation or to partial lung collapsecaused by pleural fluid.5 However, the term interstitialpattern has classically indicated that there is infiltrationof fluid or cells into the non–air-containing elements ofthe lung.5 Infiltration does not occur during incompleteinhalation or partial lung collapse; therefore, the terminterstitial pattern is misleading in these cases because itdoes not precisely represent the underlying pathogenesis.Other descriptions of atelectasis use the term alveolarpattern.5–7 This description is more appropriate becausean alveolar pattern is produced when a portion of thelung contains less than the normal volume of air due toeither the collapse of or infiltration (cells or fluid) intothe alveolar air spaces.5–7 In our experience, interstitialpattern and alveolar pattern have been used to describedifferences in severity of reduced lung size.

Another reported descriptor used for lungswith increased opacity is air-space pattern.5This term may be preferable because it canbe modified to denote severity. For example,a mild air-space pattern would correspondwith the use of interstitial pattern to denoteless severe disease with partial obscuring ofthe pulmonary blood vessels, and a severeair-space pattern would correspond with theclassic use of alveolar pattern to describe dis-ease in which the pulmonary blood vesselsare completely obscured (Figure 1). Alterna-tively, the lung may be described as havingincreased opacity that is further character-ized by the use of other descriptors (e.g., dis-tribution, lung size, air bronchograms,silhouetting of blood vessels, lines, and rings)to convey radiographic abnormalities with nomention of pattern.

THE EXPANDED LUNGConsolidation or infiltration is recognizedradiographically when a lung that is normalor increased in size has a relatively homoge-nous soft tissue opacity characterized byeffacement of pulmonary blood vessels and,sometimes, air bronchograms (Figure 2).Consolidation or infiltration always producesan air-space pattern because there is infiltra-tion of the alveoli by fluid, cells, or both. Nor-mal or increased lung size is detected byknowing the normal extent of lung lobes andidentifying bulging pleural surfaces or dis-placement of structures (mediastinum, heart,adjacent unaffected lung) away f rom theaffected lung lobe (i.e., mass effect). Althoughthe term consolidation may imply that the lungis solid, the diseases that produce consolida-tion do not always advance to that degree.Therefore, there also is a continuum of theair-space pattern from mild to severe.Recognizing that an abnormally opaquelung is normal or increased in size is impor-tant because this finding always indicates disease, andfurther evaluation using other imaging modalities(ultrasound, computed tomography), tissue sampling(transtracheal wash, bronchoalveolar lavage, percuta-neous needle aspiration, biopsy), endoscopy, or surgerymay be indicated.

THE INCOMPLETELYEXPANDED LUNGIn atelectasis, the volume of the lung is reduced becausegas in the alveoli is absorbed and not replaced orbecause the lung is poorly ventilated. During thoracicradiography, the differential diagnosis for atelectasis

September 2008 COMPENDIUM

Lung Expansion in the Diagnosis of Lung Disease 481

Figure 2. Orthogonal thoracic radiographs of a 6-year-old, spayed,mixed-breed dog that was admitted for lethargy, pyrexia, andhemoptysis.The right middle lung lobe has a severe increase in opacity thatsilhouettes with pulmonary blood vessels and summates with the heart. Airbronchograms and a lobar sign with adjacent lung lobes are also present.Thelung lobe is mildly increased in size, resulting in left displacement of the heart.These radiographic signs indicate a pattern of consolidation.

Figure 3. Orthogonal thoracic radiographs of a 12-year-old neuteredmalamute that was admitted for dental cleaning.During the dental procedure,patient ventilation became difficult, and thoracic radiography was performed toidentify the possible cause.During radiography, the dog was under general anesthesiaand positive-pressure ventilation was used. Several radiographic signs are visible:reduced size and increased opacity of the left caudal lung lobe, crowding andreorienting of pulmonary blood vessels, compensatory hyperinflation of the right lung,left mediastinal shift, cardiac rotation, left dorsal displacement of the hilus, bronchialrearrangement, cranial displacement of the left crus of the diaphragm, and left thoracicwall rib crowding.These radiographic signs indicate a pattern of atelectasis.

includes diseases and technical complications that limitexpansion of the lung, such as airway obstruction, lungcompression, incomplete inhalation, prolonged recum-bency, and respiratory dynamics during anesthesia (Fig-ures 2, 3, and 4). Although technical complications maybe unrelated to disease, they may be mistaken for diseaseor obscure substantial pulmonary lesions. Therefore, it isimportant to recognize atelectasis because it may be animportant diagnostic clue, an incidental finding, or asubstantial distracter (Figures 5 and 6).Atelectasis is a radiographic diagnosis made when thelung is reduced in size. The radiographic signs of atelec-tasis include displacement of interlobar fissures, pul-monary blood vessels, or bronchi because of reducedlung volume. Decreased lung size is typically also recog-nized by identifying increased lung opacity, cranial dis-placement of the diaphragm, displacement of themediastinum and heart toward the affected lung, com-pensatory overinflation of the adjacent lung, bronchial

rearrangement, and rib displacement (crowding).8 Thesesigns are related to the fact that a fixed thoracic volumemust be maintained. If the lung collapses, then otherstructures must compensate for the loss of volume eitherby shifting position or increasing volume. Some or all ofthese signs may be detected, depending on the severityof atelectasis (Figures 2 and 3).Usually, a reduction in lung volume is accompanied byincreased lung opacity because of the change in the bal-ance of gas-filled spaces to blood vessels (i.e., in a unit oflung tissue, there is less gas for the same amount of visi-ble soft tissue structures). The degree of lung collapsemay be minimal to severe; thus, the degree of increasedopacity (air-space pattern) is also variable.When atelec-tasis is more severe, a silhouette sign, lobar sign, or airbronchogram may be detected. However, increasedopacity is not necessary to diagnose atelectasis becausemild volume loss and pleural fissure displacement canoccur without detectable increased opacity.In humans, clinically important pleural fissure dis-placement without detectable increased lung opacity is a



Figure 4. A ventrodorsal thoracic radiograph of the samepatient as in Figure 2.This radiograph was obtained 1 daylater, while the dog was awake, to confirm that the atelectasis wascaused by technical complications associated with recumbencyand anesthesia and not by pulmonary disease.No abnormalitiesare visible.

Detect increased opacityin lung/lung lobe

Incompletelyexpanded

Disease Technicalcomplications

IncidentalObscurelesion

Atelectasis

Fullyexpanded

Consolidation

Lungsize

Disease

Figure 5. Atelectasis versus consolidation decision tree.


ographic pattern of atelectasis is detected, all types ofatelectasis generally need to be considered (Table 1). Insome instances, it may be possible to refine the differen-tial diagnosis by noting other radiographic signs, such asthe distribution of the atelectasis (i.e., focal, locallyextensive, or diffuse). A focal lesion might suggest alocal problem such as a foreign body, radiation pneu-monitis, or recumbency. A diffuse distribution mightsuggest diseases that produce cicatrizing atelectasis orincomplete inhalation. Further characterization ofatelectasis is only possible when the underlying patho-genesis can be determined.

Relaxation or Passive AtelectasisThe normal lung has an inherent elasticity and a naturaltendency to collapse. This tendency to collapse at rest isnormally opposed by the rigid shape of the thoracic walland the sealed thoracic cavity. These opposing forcesproduce negative pressure in the pleural space.Therefore,any process that allows the normally negative intrapleuralpressure to approach atmospheric pressure (either com-pletely or partially) results in lung collapse and relaxationatelectasis. Relaxation atelectasis most often is due to

• A critical initial step in the diagnostic approach toany patient undergoing pulmonary radiography is todetermine whether both lungs are fully orincompletely expanded.

• If a radiographically abnormal lung is normal tolarge in size, it is considered expanded, indicatingpulmonary disease.

• If a radiographically abnormal lung is small, it isconsidered incompletely expanded, indicatingpulmonary disease, nonpulmonary thoracic disease,or a technical complication.

• The terms infiltration, consolidation, collapse, andatelectasis can be used to describe lungs regardlessof degree of expansion; however, other radiographicsigns must be sought to make a more definitivediagnosis.

Key Points

sign of atelectasis in postanesthesia patients.3,4 Also inhumans, patterns of atelectasis associated with diseaseare categorized based on derangements of normal physi-ologic mechanisms: passive (relaxation), resorption(obstructive), adhesive, and cicatrizing. When a radi-



pleural diseases such as fluid accumulation orpneumothorax, but it may also result fromimpaired function of the thoracic wall mus-culature or diaphragm. Large thoracic walllesions, severe cardiomegaly, pulmonarylesions that occupy substantial intrathoracicvolume, or diaphragmatic hernia with cranialdisplacement of abdominal organs also mayproduce relaxation atelectasis. In mild casesof pneumothorax or pleural fluid accumula-tion, the only detectable sign may be reducedlung volume because the ratio of gas-filledspace to blood vessels is not altered enough toresult in increased opacity.Dependent portions of the lung may havedecreased alveolar expansion and increasedperfusion because of the effects of gravity.These conditions change the ratio of gas-filled spaces to blood vessels, resulting inincreased attenuation of x-rays during radi-ography or computed tomography. Theresulting appearance has been termed grav-ity-dependent atelectasis.9 Although they arenormal physiologic changes, gravity-dependent effects on the lung can exac-erbate relaxation atelectasis caused byhypoventilation. Hypoventilation is f re-quently encountered during general anes-thesia or diffuse neuromuscular diseasebecause the diaphragm and thoracic wall areinactive. During general anesthesia, relax-ation atelectasis can be easily overcome byincreasing ventilation; ordinarily, this isaccomplished by compressing the rebreath-ing bag on the patient’s breathing system tomimic maximal spontaneous inspiration (vital capacitymaneuver). Relaxation atelectasis also may occur incases of diaphragmatic hemiparesis.Atelectasis at the edge of a focal lesion is thought bysome to result from the normal elasticity of the sur-rounding lung and is therefore regarded as a variant ofrelaxation atelectasis.3,4 It is radiographically detectableonly if the focal lesion is gas filled (e.g., bulla) because ifthe focal lesion is of soft tissue consistency, the lesionand atelectatic lung will form a silhouette. In some texts,atelectasis adjacent to a parenchymal space-occupyinglesion (neoplasm, bulla) has been termed compressiveatelectasis because of the idea that an enlarging focallesion “compresses” the adjacent lung. Compressive atelec-

tasis also has been used to describe atelectasis in whichthe size of the lung has been reduced beyond its normalresting size (e.g., tension pneumothorax). In cases oftension pneumothorax, the lungs are atelectatic becauseof their own elasticity and compression caused by posi-tive intrathoracic pressure.

Resorption or Obstructive AtelectasisAir must flow into the lungs to allow them to expand.Diseases that obstruct the airways (primary bronchus,multiple small bronchi, or bronchioles) produceresorption atelectasis because gas exchange in the alve-oli continues despite the obstruction, causing any gasin the lung downstream to the obstruction to be

Figure 6. Two sets of orthogonal thoracic radiographs of a 7-year-old,spayed domestic shorthaired cat.

In these images, obtained while the cat was awake, the lungs are decreased involume and have diffuse, mildly increased opacity. Based on the cranial location ofthe diaphragm and a diffuse distribution, these radiographs most likely wereobtained during exhalation.

In these images, obtained while the cat was under general anesthesia with positive-pressure ventilation, the lungs are well expanded, demonstrating that the increasedopacity in the initial images was the result of a technical artifact rather than disease.



absorbed, and the lung lobe becomes small withincreased opacity and no air bronchograms.11If a lung has reduced size, increased opacity, and no airbronchograms, either a complete bronchial obstructionis present or an underlying disease that could secondar-ily occlude the airways with fluid or cells (e.g., pneumo-nia, neoplasm, asthma) or severe lung fibrosis (in whichthe airways are collapsed secondary to fibrotic change)should be suspected. Resorption atelectasis may or maynot be present. In humans, resorption atelectasis is notusually considered when air bronchograms are detected.This is because an obstruction of a large bronchus thatis severe enough to result in absorption of gas from thealveoli should also cause absorption of gas from thebronchial tree downstream from the obstruction.3,4 Ifonly the small bronchi are obstructed (e.g., mucus accu-mulation) in the periphery of the bronchial tree, airbronchograms are typically present because the largerairways remain patent.

resorbed. The obstruction prevents replacement of thegas; therefore, the lung collapses and becomes pro-gressively smaller. Causes of airway obstructioninclude neoplasia, foreign body aspiration (Figure 7),and mucus plugging secondary to asthma, bronchitis,pneumonia, or abnormalities of respiratory epithelialcilia. In older patients, and especially in patientsunder general anesthesia, exhalation may exceed thevolume in the lung at which bronchioles start to close(critical closing volume). If these airways are notopened by subsequent inspirations, the alveoli down-stream to the closed bronchioles collapse.10 A com-mon, naturally occurring example of resorptionatelectasis is seen in cats with chronic asthma. Inmany asthmatic cats, concurrent increased mucussecretion causes plugging of bronchi or bronchioles.Frequently, the right middle lung lobe is affected andthe lobar bronchus is chronically obstructed. Withtime, the remaining bronchiolar and alveolar gas is

Table 1. Differential DiagnosesAssociated with Radiographic Findings

RadiographicPattern Typea Pathogenesis Abbreviated Differential Diagnosis

Incompletely Relaxation Unopposed tendency of lung to • Pneumothoraxexpanded collapse due to inherent elasticity • Pleural fluid(collapsed, • Space-occupying lesionatelectatic) • Gravity dependent

• Shallow breathing

Obstructive Absorption of alveolar gas without • Neoplasmreplacement due to airway obstruction • Inhaled foreign body

• Mucus plugging (asthma)• Infectious bronchitis or pneumonia• Ciliary dyskinesis

Adhesive Lumen surfaces of alveoli stick • Neonatal respiratory distress syndrometogether due to surfactant abnormality • Acute respiratory distress syndrome

• Pulmonary embolism

Cicatrizing Lungs do not increase in volume under • Chronic idiopathic fibrosisnormal respiration due to reduced • Chronic immune-mediated lung diseasecompliance • Chronic pneumonia

• Radiation pneumonitis

Expanded NA Infiltration of lung with fluid, cells, or both • Pneumonia(infiltrated, • Neoplasmconsolidated) • Hemorrhage

• Edema (severe)• Fungal disease• Immune-mediated disease• Lung-lobe torsion

aThese terms are commonly used in human medicine but may be useful in refining radiographic diagnoses in veterinary patients.

Adhesive AtelectasisNormally, as an alveolus decreases in volume, pulmonary alveolar surfac-tant reduces surface tension in an effort to keep the alveolus open. If asurfactant abnormality is present, the luminal surfaces of the alveolar wallscan stick together and generalized alveolar collapse, called adhesive atelec-tasis, can occur. Another proposed mechanism for adhesive atelectasis isthat alveolar collapse disrupts surfactant function. Adhesive atelectasismay occur in association with pulmonary embolism and is thought torelate to decreased surfactant production. However, the exact cause of sur-factant derangements seen with pulmonary embolism is not fully under-stood. Atelectasis may be an important radiographic sign of pulmonarythromboembolism; however, atelectasis in these patients may be transient.4Atelectasis is reportedly seen in many patients with pulmonary embolism(i.e., the presence of a foreign object, such as a bone fragment or air bub-ble, that lodges in a pulmonary artery) but is nonspecific for thromboem-bolism (i.e., the presence of a blood clot in a pulmonary artery).12–14Surfactant function may remain altered despite reopening of the collapsedair spaces.15

Cicatrizing AtelectasisLung volume depends on a balance of applied forces resulting in negativeintrathoracic pressure and the opposing elastic forces of the lung. Theability of the lungs to stretch and change in volume relative to an appliedchange in pressure is called pulmonary compliance. The normal lung ismore compliant in a low-volume state and becomes less compliant as thevolume increases. Diseases that reduce lung compliance prevent the lungsfrom increasing in volume during normal respiration; this is termed cica-trizing atelectasis. Lung compliance most often is reduced by fibrosis,which produces a “stiffer” lung, or by scar tissue. Increased radiographicopacity may be the result of fibrosis and the inability to expand the alveoliwith gas. In animals, fibrosis and scar formation are most often caused bychronic pneumonia, immune-mediated disease (e.g., chronic obstructivepulmonary disease), and radiation pneumonitis. Chronic idiopathic pul-monary fibrosis of West Highland White terriers is a reported diseaseentity. In this small population of dogs, diffuse cicatrizing atelectasis maybe present as a secondary change; however, such conclusions have not beenreported.16,17

CONCLUSIONThe terms atelectasis, collapse, inf iltration, and consolidation are commonlyused to describe pulmonary radiography findings; however, other radi-ographic signs must be sought to make a more definitive diagnosis.Although many of the diseases that produce consolidation can also produceatelectasis, it is important to differentiate the two conditions when possible.Recognizing that an abnormally opaque lung is normal or increased in sizeis important because this finding always indicates disease.Atelectasis (increased radiographic opacity and decreased size of the lung)may be an essential diagnostic clue, an incidental finding, or a substantial dis-tracter. Although increased opacity is a common radiographic finding in



atelectasis, it is not necessary to make this radiographicdiagnosis; detecting reduced lung size is all that is neces-sary. When a radiographic pattern of atelectasis isdetected, then all types of atelectasis generally need to beconsidered. In some instances, it may be possible to refinethe differential diagnosis by noting other radiographicsigns. Further characterization of atelectasis is only possi-ble when the underlying pathogenesis can be determined.

REFERENCES1. Stedman’s Medical Dictionary. 28th ed. Philadelphia: Lippincott, Williams,and Wilkins; 2005.

2. Dorland ’s Illustrated Medical Dictionary. 30th ed. Philadelphia: Saunders;2003.

3. Fraser RG, Pare JAP. Diagnosis of the Diseases of the Chest. 4th ed. Philadel-phia: Saunders; 1999.

4. Webb WR, Higgins CB. Thoracic Imaging:Pulmonary and CardiovascularRadiology. Philadelphia: Lippincott,Williams and Wilkins; 2005.

5. Thrall DE. Textbook of Veterinary Diagnostic Radiology. 4th ed. Philadelphia:Saunders; 2002.

6. Myer W. Radiography review: the alveolar pattern of pulmonary diseases. JAm Vet Radiol Soc 1979;20:10-14.

7. Suter PF, Chan KF. Disseminated pulmonary diseases in small animals: aradiographic approach to diagnosis. J Am Vet Radiol Soc 1968;9:67-79.

8. Reed JC. Chest Radiology: Plain Film Patterns and Differential Diagnoses. 4thed. St. Louis: Mosby; 1997.

9. Woodring JH, Reed JC. Types and mechanisms of pulmonary atelectasis. JThorac Imaging 1996;11:92-108.

10. Lumb AB. Nunn’s Applied Respiratory Physiology. 5th ed. Oxford: Butter-worth-Heinemann; 2000.

11. Sherding RG. The Cat: Diseases and Clinical Management. 2nd ed. New York:Churchill-Livingstone; 1994.

12. Worsley DF, Alavi A, Aronchick JM, et al. Chest radiographic findings inpatients with acute pulmonary embolism: observations from the PIOPEDstudy.Radiology 1993;189:133-136.

13. Coche EE, Muller NL, Kim K, et al. Acute pulmonary embolism: ancillaryfindings at spiral CT.Radiology 1998;207:753-758.

14. Stein PD,Terrin ML, Hales CA, et al. Clinical, laboratory, roentgenographic,and electrocardiographic findings in patients with acute pulmonary embolismand no pre-existing cardiac or pulmonary disease.Chest 1991;100:598-603.

15. Magnusson L, Spahn DR. New concepts of atelectasis during general anes-thesia. Br J Anaesth 2003;91:61-72.

16. Bonagura JD,Hamlin RL,Gaber CE. Chronic respiratory disease in the dog.In: Kirk RW, ed. Current Veterinary Therapy X. Philadelphia: WB Saunders;1989:361-368.

17. Corcoran BM, Cobb M, Martin MWS, et al. Chronic pulmonary disease inWest Highland white terriers. Vet Rec 1991;144:611-616.



Figure 7. Ventrodorsal thoracic radiographs of a 2.5-year-old, intact,male English springer spaniel obtainedbefore and after removal of a foreign body (plant awn)from the bronchus leading to the right caudal lung lobe.

Before removal ofthe foreign body, apattern of atelectasisis evident: the rightcaudal lung lobe issmaller (lessexpanded) and hasincreased opacitycompared with thesecond image.Theribs also appearcloser together, andthere is a mediastinalshift to the right.Initially, the right crusof the diaphragmappeared craniallydisplaced, but thisappearance did notchange over time.

After removal ofthe foreign body.

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