Thorax, 1980, 35, 745-750

Unilateral hyperlucent lung: the case for investigationSHEILA A McKENZIE, D J ALLISON, M P SINGH, AND S GODFREY

From the Department of Paediatrics and Neonatal Medicine and Department of Diagnostic Radiology,Hammersinith Hospital, London

ABSTRACT Seventeen children with unilateral hyperlucent lungs were referred for investigation.Of the 11 who had a referring diagnosis of possible Macleod's syndrome only two were shownto have post-viral bronchiolitis. Three of the 11 had conditions that required surgical treatmentand a further two with bronchiectasis were treated medically. To avoid confusion we suggestthat Macleod's syndrome is reserved exclusively for children with post-viral bronchiolitis. Radio-isotopic regional lung function studies were useful in the investigation of the subjects from threepoints of view. Firstly, they distinguished children with primary perfusion abnormalties andnormal ventilation, secondly, they defined the extent of altered respiratory function, and thirdly,they were able to distinguish compensatory emphysema from congenital lobar emphysema. Asbronchography and bronchoscopy may be hazardous in small children with poor respiratoryreserve, such regional studies may be useful in indicating which patients do not require furtherinvasive investigation.

Of the many causes of unilateral hyperlucent lungin children, congenital lobar emphysema andforeign body inhalation are among the most com-mon. In general neither of these conditions isdifficult to diagnose and the affected lung, or lobe,is usually hyperinflated. There is, however, asmall group of children with hyperlucent lungs inwhom the diagnosis is not immediately apparent.Unilateral hyperlucent lungs which are normal orsmall in size are occasionally seen on radiographsin children who present with longstanding respir-atory symptoms. Macleod's or Swyer-James syn-drome' 2 presents in this way and is now believedto follow respiratory infections such as measles,3adenovirus,4 and mycoplasma.3 5 Bronchogramsshow poor filling of the peripheral bronchi andhistologically the bronchi and bronchioles showevidence of chronic inflammatory changes. Someclinicians nevertheless prefer to use the termMacleod's syndrome simply to describe the radio-graphic appearances and do not imply anyaetiology.Over the past three years 17 children with uni-

lateral hyperlucent lungs have been referred to usfor investigation. In many of these children the

Address for reprint requests: Dr SA McKenzie, Department of Paedi-atrics and Neonatal Medicine, Hammersmith Hospital, Du CaneRoad, London W12 OHS

aetiological diagnosis was uncertain at the time ofreferral; 11 were referred with a possible diagnosisof Macleod's syndrome. We describe here the re-sults of our investigations and suggest a line ofinvestigation for children presenting in this way.

Methods

The age of patients, history, presenting symptomsand signs, chest radiograph appearances, andinitial diagnoses are shown in table 1. Seven chil-dren were known to have congenital heart diseasebut it was not clear whether their respiratorysymptoms and radiographic appearances wererelated entirely to this or whether they had ad-ditional pulmonary disease. Taking the group as awhole the diagnosis of Macleod's syndrome hadbeen considered at some time in 11 children. Atthe time of referral, four of these children hadsmall hyperlucent lungs, six had lungs of normralsize, and one (patient 12) had a large hyperlucentlung which had appeared of normal size previously.

All children had chest radiographs and fluor-oscopy and underwent regional lung functionstudies. These were carried out using nitrogen-13.Both bolus inhalation and bolus injection studieswere carried out.6 The distribution of gas andblood throughout both lung fields was determined.The clearance of gas from the lungs after bolus

745

on August 30, 2021 by guest. P

rotected by copyright.http://thorax.bm

j.com/

Thorax: first published as 10.1136/thx.35.10.745 on 1 O

ctober 1980. Dow

nloaded from

Sheila A McKenzie, D J Allison, M P Singh, and S Godfrey

Table 1 Patients' ages, presenting symptoms, chest radiographic appearances, and initial diagnosis

Patient Age Presenting symptons/signs Chest radiographic appearance Referring/initial diagnosisand history

1 2 yr Chronic respiratory failure. Small hyperlucent left lung ?Macleod's syndrome"Measles" age 1 yr. Highadenoviral titres

2 9 mo Wheezing since age 6 wk

3 11 yr Pertussis aged 4 mo andpneumonia. Haemoptysis age I vr

Recurrent chest infections

Recurrent wheezing

6 2 yr Recurrent chest infections andwheezing since age 3 mo

7 4 yr Short of breath on exercise.Known ventricular septal defect

8 7 yr Murmur since birth. Valvarpulmonary stenosis at cardiaccatheterisation. Asymptomatic

9 3 mo Patent ductus arteriosus ligatedage I mo. Persistent tachypnoea

10 4 days Respiratory distress from birth

I1 4 mo Respiratory distress and cardiacmurmur from birth

12 6 mo Tachypnoea during infancy

13 13 mo Endocardial fibroelastosis.Tachypnoea for six mo

14 12 yr Mustard repair of transpositiongreat vessels age 4 yr. Recurrentwheezing since

15 5 mo Ventricular septal defect. Referredage 2 mo. Persistent tachypnoeaand wheeze

16 2-5 yr Recurrent chest infection andwheeze

17 1 yr Cardiac murmur. Knownunilateral pulmonary artery.Poor exercise tolerance

Changes suggestive of right middle lobe andlower lobe disease up to 6 mo. Age 9 mo,hyperlucent sniall right lungRecurrent collapse/consolidation left lower lobein early childhood. Hyperlucency left lower zoneage II yr. Lung of normal sizeHyperlucent left lung of normal size

Normal until age 3 yr; subsequently smallhyperlucent left lungHyperlucent left lung of rormal size

Hyperlucent left upper zone. Left lung of normalsizeSmall hyperlucent left lung on routine X-ray

Hyperlucent large left upper lobe

Hyperlucent large left lungHyperlucent right middle lobe

Hyperlucent large left lung which looked to be ofnormal size on previous filmsHyperlucent left lung of normal size

?Macleod's syndrome

?Macleod's syndrome

?Macleod's syndrome?Macleod's syndrome

?Macleod's syndrome

?Macleod's syndrome

?Macleod's syndrome

Congenital lobar emphysema

Respiratory distress syndrome?Congenital lobar emphysema?Compensatory emphysema?Macleod's syndrome

?Macleod's syndrome

Hyperlucent left upper zone. Left lung of normal Asthmasize

Hyperlucent left lung. Size normal large or small ?Congenital lobar emphysemaon different X-rays ?Compensatory emphysema

Hyperlucent left lung of normal size

Small hyperlucent right lung

?Macleod's syndrome

Unilateral pulmonary artery.?Ventilatory function of right lungbefore surgery

inhalation represented fractional ventilation andwas determined for each of four areas, right andleft upper and lower zones. The clearance of gasfrom the lungs after the injection study reflectedventilation of perfused areas. Thus any delay inclearance of 13N suggested gas trapping and any

difference in the rates of clearance after inhalationand injection studies represented ventilation-perfusion imbalance. Depending on the results ofthe regional studies further investigations werecarried out as detailed in table 2.Ten children in whom a definite diagnosis re-

mained uncertain after the regional studies were

referred for bronchoscopy or bronchography or

both. Bronchography was performed under generalanaesthetic, and where previous investigations hadindicated the possibility of an abnormality of one

of the principal bronchi, the bronchogram was

preceded by bronchoscopy which was performedin the radiology department during the same

anaesthetic. After bronchoscopy an endotrachealtube was inserted and a pre-curved nylon cannula(OD 2-1 mm; Portex Ltd) passed through the tubeinto the lungs. A suspension of propyliodone BPwas used for bronchography (Dionosil Oily, GlaxoLaboratories Ltd) which was performed underfluoroscopic control with appropriate films exposedfrom an under-couch tube (focal spot 06 mm).Where the respiratory reserve was adequate bi-lateral bronchograms were obtained, the lungsbeing catheterised selectively in turn. Where ab-normal variations in bronchial calibre were ob-served during fluoroscopy, they were recorded on

70 mm film exposed at three frames per second.

45

6 yr6 yr

746

on August 30, 2021 by guest. P

rotected by copyright.http://thorax.bm

j.com/

Thorax: first published as 10.1136/thx.35.10.745 on 1 O

ctober 1980. Dow

nloaded from

Unilateral hyperlucent lung: the case for investigation

Table 2 Investigations and final diagnoses

Patient Other investigations Final diagnosis

I Fluoroscopy-mediastinal movement to hyperlucent side oninspiration. Bronchoscopy-no bronchial obstruction seen.Open lung biopsy-chronic round cell infiltrate aroundbronchioles

2 Bronchogram-narrowed RML and RLL bronchi with poorperipheral filling.RML and RLL lobectomies for repeated pneumonia-chronicround cell infiltrate around bronchioles

3 Bronchoscopy-white tenacious sputum from LLL bronchus.Bronchogram-saccular bronchiectasis lingula and LLL

4 Bronchoscopy-compression of posterior wall of L mainbronchus with pulsation in time with cardiac cycle

5 Fluoroscopy-no mediastinal shift.Bronchoscopy-granulations almost occluding L main bronchus.Histology of granulations-chronic inflammatory tissue

6 Cine-bronchogram-collapse of L main bronchus duringexpiration

7 Arteriogram-branch stenosis of L pulmonary artery

8 Further investigation not planned at present9 LUL lobectomy. Emphysematous lung. Bronchi not

histologically examined10 LUL lobectomy. Accident in preparation of specimenII Bronchogram-RML bronchial narrowing. Collapse of L main

bronchus during expiration.RML lobectomy-reduction in cartilaginous plates throughoutbronchi

12 Bronchogram-narrow segment L main bronchus.Barium swallow-L sided oesophageal compression

13 Cardiac catheterisation-fibroelastosis. All chambers grosslydilated

14 Bronchogram-narrowed orifice of LLL bronchus. Otherbronchi normal

15 Further investigation not necessary

16

17

Bronchogram-bilateral bronchiectasis. Crowding andnarrowing ofLUL and LLL bronchiFurther investigation not necessary

Macleod's syndrome with bilateral disease (on the basisof regional studies)

Macleod's syndrome

Bronchiectasis

Probable abnormal position of left main pulmonaryartery (no further investigations permitted)Occlusion of L main bronchus casuse by granulations?secondary to inhaled foreign body. Symptoms andchest X-ray improved after removalBronchomalacia

Branch pulmonary artery stenosis and ventricular septaldefectPulmonary stenosis (valvar)Congenital lobar emphysema-LUL

Congenital lobar emphysema-LULCongenital lobar emphysema-RML with L mainbronchial narrowing.Aortic stenosis

Tracheal cyst-surgically removed.Patient curedEndocardial fibroelastosis. ?Compression L main bronchuscaused by large L atrium (Incomplete investigation,postmortem not permitted)Compensatory emphysema 20 to partial left lower lobecollapse.Congenital lobar empnysema-L lung (managedconservatively)Bilateral bronchiectasis

Absent L main pulmonary artery. Function of L lungnormal

LUL=left upper lobe, LLL=left lower lobe, RML=right middle lobe, RLL=right lower lobe.

Results

Chest fluoroscopy to examine diaphragmatic andmediastinal respiratory movements was performedin all 17 children but in all but two (patients 1and 5) no abnormality was demonstrated. Patient 1,one of the two children given a final diagnosis ofMacleod's syndrome, had characteristic movementof the mediastinum towards the hyperlucent sideon inspiration.Regional lung function studies showed that in

all cases except one (case 14) the peak counts inboth inhalation and infusion studies suggested thatthere was reduced gas and blood reaching thehyperlucent areas in comparison to the otherareas. In case 14 the hyperlucent area received

more gas and blood than the other areas. Thischild was subsequently shown to have partial leftlower lobe collapse not evident on chest radio-graph and thus had compensatory emphysema.Three children (patients 7, 8, and 17) showed

normal rates of clearance of gas from all regionsof both lungs after inhalation and infusion, des-pite the reduction in peak counts in the hyper-lucent areas. All had abnormal pulmonary vascularanatomy-unilateral peripheral pulmonary arterystenosis (patient 7), pulmonary valve stenosis(patient 8), and absent pulmonary artery (patient17). Thus these children had hyperlucent lungswhich were relatively underperfused but had nor-mal ventilatory function. Bronchoscopy and bron-chography were therefore not necessary as their

747

on August 30, 2021 by guest. P

rotected by copyright.http://thorax.bm

j.com/

Thorax: first published as 10.1136/thx.35.10.745 on 1 O

ctober 1980. Dow

nloaded from

Sheila A McKenzie, D J Allison, M P Singh, and S Godfrey

symptoms and radiographic appearances could berelated entirely to their congenital heart disease.Nine patients (2-6, 9, 10, 12, and 13) had de-

layed clearance of gas from the hyperlucent lungor area only. One child (patient 14) had normalclearance from his hyperlucent left upper zonebut delayed clearance from the lower zone on thesame side. All of these children except one whowas too ill (patient 13) proceeded to bronchoscopyand/or bronchography, or surgery.Four patietts (1, 11, 15, and 16) showed delayed

rates of clearance from both lungs suggestinggeneralised poor ventilatory function. Patient 1was in severe respiratory failure and it was con-sidered unwise to perform bronchography. Anendoscopic lung biopsy showed histological changesconsistent with post-viral bronchiolitis. Patient 11was shown at bronchography to have narrowingof the left main bronchus on expiration as well asnarrowing of the right middle lobe bronchus (fig-ure). This child underwent right middle lobectomyand one year later is asymptomatic. Repeatregional studies now show normal clearance ratesfrom both sides. Patient 15 had delayed clearancefrom the hyperlucent left lung as well as the col-lapsed right upper lobe although clearance fromthe rest of the right lung was normal. These re-sults suggested that the hyperlucency of the leftlung was not caused by compensatory emphysemabut by emphysema secondary to airway obstruc-tion. This child's symptoms have improved withoutsurgical intervention. Patient 16 had bilateralbronchiectasis and was discharged abroad to bemanaged medically.

Treatment and outcome

Three patients (patients 9, 10, and 11) had lobec-tomies for congenital lobar emphysema and wouldhave had this treatment whether or not regionalstudies and bronchography had been carried out.Nevertheless both surgeon and anaesthetist hadthe benefit of knowing the function of the otherlung and lobes. In patients 9 and 10 this wasnormal but in patient 11 the opposite main bron-chus was stenosed. Three other children, all re-ferred as Macleod's syndrome, underwent surgery.One had a tracheal cyst (patient 12) and had beenwheezing since birth. Another (patient 2) under-went right middle and right lower lobe lobectomiesbecause of recurrent pneumonia. Both lobesshowed changes consistent with post-viral bron-chiolitis. The third (patient 5) had a granulomaremoved from the left main bronchus. Beforesurgery this child's chest radiograph had shown

that the left lung was small and hyperlucent. Thisappearance returned to normal after surgery.All children who underwent surgery respondedfavourably.

Figure Chest radiograph (a) of patient 11 and framefrom cine-bronchogram (b) taken in expiration. Thechest radiograph shows hyperlucency of the right midzone and the bronchogram shows almost completeocclusion of the left main bronchus on expiration inaddition to stenosis of the right middle lobe bronchus.

748

on August 30, 2021 by guest. P

rotected by copyright.http://thorax.bm

j.com/

Thorax: first published as 10.1136/thx.35.10.745 on 1 O

ctober 1980. Dow

nloaded from

Unilateral hyperlucent lung: the case for investigation

Two children had bronchiectasis. In patient 16,regional function studies and bronchography sug-gested bilateral disease, not evident from the chestradiograph. The site of pathology is clearly impor-tant in planning physiotherapy. The child withpartial left lower lobe collapse underwent physio-therapy and is now well.Apart from the child with endocardial fibro-

elastosis who died, the remaining children weremanaged conservatively.

Discussion

This study emphasises the variety of causes ofunilateral hyperlucent lungs. Of the 11 childrenreferred with a diagnosis of possible Macleod'ssyndrome post-viral bronchiolitis was the finaldiagnosis in only two and regional studies suggestedthat one of these had bilateral disease. As someof these children had surgically treatable con-ditions and others had abnormal pulmonary vas-culature only, we feel that the terms "Macleod'ssyndrome" and "Swyer-Jones syndrome" shouldbe reserved only for children in whom other causesof respiratory symptoms have been ruled out. In-vestigation for many children meant not only achange in diagnosis but a significant change intreatment. Patients 5, 12, and 16 for example hadbeen wheezing for some time before being referred.Regional studies were useful initial investiga-

tions for three reasons. Firstly they distinguishedchildren with unequal pulmonary perfusion in theabsence of primary lung disease. Several forms ofcongenital heart disease other than branch pul-monary stenosis are associated with unequal lungvascularity.7 8 Although the distribution of venti-lation favoured the well-perfused lung, the venti-latory turnover on both sides was normal. Previousstudies with 99mTechnetium and 133Xenon9 10 haveshown similar findings in children with unilateralpulmonary artery and recent studies in newbornanimals have shown that when the pulmonaryartery supply is interrupted to one lung, that lungfails to grow normally, remaining abnormallysmall." Thus the results of the ventilation scanin the three children with primary perfusion ab-normalities suggest that the under-perfused regionswere small in comparison to the other regions.Secondly, regional studies were useful in identify-ing children with bilateral disease. Congenital lobaremphysema usually affects only one lobe of onelung'2 but occasionally the presence of bilateraldisease may not be appreciated, as in patient 11in this series. Abnormal variations in bronchialcalibre were seen on fluoroscopy at bronchography

possibly due to soft bronchial cartilage. Repeatstudies were of interest in the follow-up of thischild and demonstrated, as others have,l3 thatinfantile lobar hyperinflation does improve overthe first year of life in some children. Thirdly, theinterpretation of chest radiographs showing areasof hyperlucency together with areas of collapsemay be difficult, particularly if the radiographicsigns change from day to day as in patient 15.These signs may be the result either of lobar col-lapse with compensatory emphysema or collapsesecondary to congenital lobar emphysema. Incompensatory emphysema gas and blood are bothdistributed principally to areas of hyperlucencyand clearances are normal, as in patient 14. Incongenital lobar emphysema, however, the hyper-lucent areas are poorly ventilated and perfused asin patients 9 and 10.

Fluoroscopy may be helpful if definite medi-astinal shift is seen. Characteristically on expirationthe mediastinum moves away from the hyperlucentside in Macleod's syndrome and when there isbronchial narrowing and air trapping. However,in our experience fluoroscopy was not very usefulbecause we rarely saw definite shift. Fluoroscopyin patient 5, for example, was inconclusive. Bron-choscopy and bronchography are not easy pro-cedures in children, particularly in those with poorrespiratory reserve. Thus regional studies may notonly help in distinguishing those children in whomthese procedures are unnecessary but also helpin localising the areas of good and poor function,of interest to anaesthetist, radiologist, and surgeon.

Nitrogen-13 was used in this study because itwas available to us and because we were interestedin evaluating its usefulness. Technetium-99m andKrypton-81m for perfusion and ventilation studiesrespectively are more readily available. As it isnow possible to measure the rate of clearance of81"Kr from the lungs, information about thedistribution of pulmonary blood flow and venti-lation in children with lungs of unequal size shouldbe more easily obtainable using a combination ofthese isotopes.

This study has shown that a significant pro-portion of children referred to us with hyperlucentlungs had treatable disorders and thereforemerited careful investigation. To avoid confusionwe suggest that Macleod's syndrome is reservedexclusively for children with post-viral bronchi-olitis and should not be used as a blanket diagnosisfor unilateral hyperlucent lungs for which thereis no obvious aetiology. If regional studies areavailable to the clinician they may be helpful inindicating children who do not need further in-

749

on August 30, 2021 by guest. P

rotected by copyright.http://thorax.bm

j.com/

Thorax: first published as 10.1136/thx.35.10.745 on 1 O

ctober 1980. Dow

nloaded from

Sheila A McKenzie, D J Allison, M P Singh, and S Godfrey

vasive investigation and in defining the extent ofaltered respiratory function.

We are grateful to the staff of the MRC cyclotronunit who provided the isotope, to Dr M Fitz-patrick and Miss M Tooley for helping with theregional lung function studies, and to our col-leagues who referred many of the patients.

References

1 Macleod WM. Abnormal transradiancy of onelung. Thorax 1954; 9:147-53.

2 Swyer PR, James GCW. A case of unilateralpulmonary emphysema. Thorax 1953; 8:133-6.

3 Reid L, Simon G, Zorab, RA, Seidelin R. Thedevelopment of unilateral hypertransradiancy ofthe lung. Br J Dis Chest 1967; 61:190-2.

4 Cumming GR, MacPherson RI, Chernick V.Unilateral hyperlucent lung syndrome in children.J Pediatr 1971; 78:250-60.

5 Stokes D, Sigler A, Khouri NF, Talamo RC. Uni-lateral hyperlucent lung (Swyer-Jones syndrome)

after severe Mycoplasma pneumoniae infection.Am Rev Respir Dis 1978; 117:145-52.

6 Ronchetti R, Stocks J, Freedman N, Glass H,Godfrey S. The clinical application of regionallung function studies in infants and small childrenusing "N. Arch Dis Child 1975; 50:595-603.

7 Whitley JE, Rudhe U, Herzenberg H. Decreasedleft lung vascularity-congenital left to rightshunts. A cta Radiolo (Diagn) 1963; 1 NS: 1 125-3 1.

8 Wilson WJ, Amplatz K. Unequal vascularity intetralogy of Fallot. AJR 1967; 100:318-21.

9 Moser KM, Guisan M, Cuomo A, Ashburn WL.Differentiation of pulmonary vascular fromparenchymal diseases by ventilation/perfusionscintiphotography. Ann Intern Med 1971; 75:597-605.

10 Treves S, Ahnberg DS, Laguarda R, Strieder DJ.Radionuclide evaluation of regional lung functionin children. J Nucl Med 1974; 15:582-7.

11 Haworth SG. Personal communication, 1980.12 Lincoln JCR, Start J, Subramanian S et al. Con-

genital lobar emphysema. Ann Surg 1970; 173:55-62.

13 Shannon DC, Todres ID, Moylan FMB. Infantilelobar hyperinflation: expectant treatment. Pedi-atrics 1977; 59:1012-8.

750

on August 30, 2021 by guest. P

rotected by copyright.http://thorax.bm

j.com/

Thorax: first published as 10.1136/thx.35.10.745 on 1 O

ctober 1980. Dow

nloaded from