Title Radiological conference. Left upper lobe collapse

Author(s) Wong, LLS; Peh, WCG

Citation Hong Kong Practitioner, 1998, v. 20 n. 9, p. 513-517

Issued Date 1998

URL http://hdl.handle.net/10722/44672

Rights This work is licensed under a Creative Commons Attribution-NonCommercial-NoDerivatives 4.0 International License.

RADIOLOGICAL CONFERENCE

Clinical History:

A 69-year-old woman suffering from nasopharyngeal carcinoma underwent a difficult but eventually successfulintubation in the intensive care unit. She was subsequently found to have poor oxygen saturation despite administrationof 100% oxygen. Serial frontal chest radiographs were obtained with the first radiograph (Figure 1) taken 20 hoursprior to the second radiograph (Figure 2).

Figure 1: Frontal chest radiograph Figure 2: Frontal chest radiograph, taken 20hours later

What is the diagnosis?

i a) Left pleural effusion

| b) Left upper lobe collapse1

I c) Right tension pneumothoraxi

d) Left lower lobe collapse

e) Progressive massive fibrosis

| This radiology case was prepared by: Dr. L.L.S. Wong,Senior Medical Officer.Professor W.C.G. Peh,Department of Diagnostic Radiology,The University of Hong Kong,Queen Mary Hospital.

513

Radiological Conference

RADIOLOGICAL CONFERENCE

Answer:

b) Left upper lobe collapse

Radiological findings

The first chest radiograph (Figure 3) shows anendotracheal tube in the trachea with its tip located about4cm p rox ima l to the ca r ina . Both l u n g s are ofsymmetrical expansion and densi ty . The subsequentchest radiograph (Figure 4) shows diffuse opacity of theleft lung only . There is loss of left lung volume as

Figure 3: Same figure as Figure 1 withaddition of arrows. Endotrachealtube is in the trachea with its tip(arrowheads) 4 cm proximal to thecarina (large arrow). There is acalcif ied density in the righttracheobronchial region, compatiblewith a calcified lymph node (openarrow). Aortic knuckle (short whitearrow) and the left cardiac border(small white arrows) are sharp anddistinct

Figure 4: Same figure as Figure 2 withaddition of arrows. Malplacedendotracheal tube with its tip(arrowheads) in the left lower lobebronchus. There is shift of themediastinum and the calcifiedlymph node (open arrow) to the left.The left hemidiaphragm is raisedbut still distinct (arrows). The aorticknuckle and left cardiac border areobscured

evidenced by left hemidiaphragm elevation, marked shiftof medias t ina l s t ructures to the left side, and mi ldcrowding of the lef t r ibs. The ou t l ine of the lefthemidiaphragm is still visible. The left cardiac borderis obliterated and the aortic knuckle is obscured. Inaddition, there is shift of the calcified subcarinal lymphnode to the left, compared with the earlier radiograph.The right lung is normal. Chest radiographic appearancesare typical of those of a left upper lobe collapse.

The cause of left upper lobe collapse is due to amalpositioned endotracheal tube which, in the secondradiograph, is located in the left lower lobe bronchus.The endotracheal tube was withdrawn and a repeat chest

514

Hong Kong Practitioner 20 (9) September 1998

RADIOLOGICAL CONFERENCE

radiograph (Figure 5) shows satisfactory positioning ofthe endotracheal tube within the trachea. There isresolution of the left-sided lung opacity, particularly inthe upper zone. There remains a small left pleuraleffusion. Appearances are those of re- inf la t ion of apreviously-collapsed left upper lobe.

Discussion

Partial or complete loss of volume of a lung isreferred to as collapse or atelectasis.1 Types of atelectasisinclude: obstructive/resorptive (obstructed bronchus withresorp t ion of gases in the a lveo l i which are not

Figure 5: Repeat chest radiograph after with-drawal of the endotracheal tube.The tip of endotracheal tube(arrowheads) is repositioned in thetrachea proximal to the carina (largearrow). There is resolution of theleft upper lobe collapse with part ofthe aortic knuckle (short whitearrow) and left cardiac border beingvisible again. A small left pleuraleffusion is seen

replenished), compressive (intrapulmonary abnormalitiesthat compress surrounding lung e.g. large lung mass),passive (developing from changes in intrapleural pressuree.g. air or f luid in the pleural space), c i ca t r i z ing(abnormally stiff lung with decreased lung compliancee.g. pulmonary fibrosis, bronchiectasis) and adhesive(deficiency of surfactant with collapse of alveoli e.g.hya l ine membrane disease or respira tory d i s t resssyndrome). Airway obstruction is by far the mostcommon cause of a t e l e c t a s i s . 2 The causes aresummarised in Table 1.3

In children, foreign body or mucus plugging arecommon causes whi le in older patients, bronchogeniccarcinoma should be considered first. In this case, theleft upper lobe orifice was obstructed by the inflated air-cuff at the distal end of the endotracheal tube. There wasno collapse of the r ight lung as there was no r ightbronchial tree obstruction, hence air could still enter thelung via the remaining space between the trachea and theendotracheal tube (Figure 6).

2. Mucus plug fr3. Misplaced4. Aspergillo

l. Carcinoma of the bro

. E x t r a - l u m i n a l • ' • • : ' : • • '••-•'" " ' . • ' • ' • '^/ ' •• ' ." ' . • . 'V • ' • " ' • • ' • " ' • •. - 1 . . ; ; .Lymph node. - . • • ' ; . • ' • - ' : ; ' . ^ . • . • • • . • • . v ' . ' • . -

2 .. Mediastinal tumour : . ' . . : - ' ' : ' . - . " ' . . • ; ' . • . •3 : Enlarged left atrium. . • ; . . : ; ;• . :. - . • • : . • . - • • • • > . . .;>x

"4.: Vascular - aortic aneurysm or anomalous

515

Radiological Conference

RADIOLOGICAL CONFERENCE

The radiological appearances in pulmonary collapsedepends upon on the mechanism of collapse, degree ofcollapse, presence or absence of consolidation, and pre-exist ing state of the pleura. Radiological signs ofcollapse may be direct or indirect. Direct signs includedisplacement of interlobar fissures, loss of aeration withincreased density of the collapsed lung, and crowding ofvascular and bronchial tree. Indirect signs are thoseresult ing from compensatory changes occurring inresponse to volume loss and include elevation of thed iaphragm, medias t ina l sh i f t , h i la r d i sp lacement ,crowding of ribs, cardiac rotation, and compensatoryhyperinf la t ion of the normal lung . 1 On occasion, thechange in position of an abnormal structure such as acalcified granuloma may also provide additional clues tothe diagnosis,2 such as in this case.

Figure 6: Line drawing illustrating the positionof the endotracheal tube (arrow-heads) within the left bronchus. Theinflated air-cuff (hatched lines)around the tip of the endotrachealtube obstructs the orifice of the leftupper lobe bronchus (LB), causingthe left upper lobe collapse. Rightmain bronchus is labelled (R)

Another i m p o r t a n t r ad iog raph ic s ign in theinterpretation of chest radiographs is the silhouette signdescribed by Felson. On a chest radiograph, a soft tissuedensity s tructure wi l l have clear and sharp marginsprovided that their interfaces with the adjacent air in thelung are reasonably smooth and tangential to the x-raybeam. The silhouette sign indicates loss of the silhouetteof any of these borders caused by an adjacent opacity ofsimilar density. Thus, when air in the lung at a softt i s sue -a i r in terface is removed (e.g. atelectasis) ors u b s t i t u t e d (e.g. c o n s o l i d a t i o n ) , the rad iographicboundary w i l l disappear. On the other hand, if theinterface is merely overlapped by a remote opacity, then,given appropriate radiographic factors, the radiographicboundary remains clearly visible within the new opacity.Thus, using this radiographic sign, normal structures andobvious abnormal opacities can be localised.4

In lef t upper lobe collapse, there is anteriordisplacement of the entire oblique fissure which becomesoriented in a plane almost parallel to the anterior chestwall . This is apparent on the lateral projection as anelongated opacity extending from the apex and reachingor almost reaching the diaphragm. This opacity isbordered posteriorly by the oblique fissure which appearssharp as it is tangential to the x-ray beam. In the frontalprojection, however, the oblique fissure is almostperpendicular to the x-ray beam. As a result, theincreased opacity of the collapsed left upper lobe does nothave a sharp border as the oblique fissure is not tangentialto the x-ray beam. Instead, left upper lobe collapseappears as a vei l- l ike opacity with a hazy marginspreading outwards, upwards and downwards from theleft hilum.4

In addition, the left cardiac border and aortic knucklewhich are normally outlined by air in the adjacent lungbecome obliterated or "silhouetted" by the increasedopacity of the collapsed left upper lobe lying adjacent tothese structures. Pulmonary vessels that are seen throughthis opacity are those in the hyperinflated left lower lobe. *In severe left upper lobe collapse, however, compensatoryhyperinflation of the left lower lobe may intrude mediallyand at the lung apex, leading to a t ranslucent bandad jacen t to the m e d i a s t i n u m and g i v i n g r ise toradiographic reappearance of the aortic knuckle border.1-4

516

Hong Kong Practitioner 20 (9) September 1998

RADIOLOGICAL CONFERENCE

Left pleural effusion

Pleural effusion is one of the causes of increaseddensity of a hemithorax. When a patient is supine, theeffusion gravitates posteriorly, producing a generalisedincreased density with an apical cap of fluid. ' Themediastinum remains central in a small effusion butbecomes displaced away from the opacified hemithoraxin a large effusion. A large effusion with no mediastinalshift, however, implies underlying lung collapse which inan older person, is often secondary to a bronchialcarcinoma.3 In this case, the mediastinal shift towardsthe hemithorax is contrary to that associated with pleuraleffusion, excluding this diagnosis.

Right tension pneumothorax

In tension pneumothorax, there is air-trapping in thepleural cavity as air enters the pleural space on inspirationbut does not leave on expiration (ball-valve effect). Asintrapleural pressure increases, this may lead to massivedisplacement of the mediastinum away from the side ofpneumothorax, compression of the ipsilateral lung(passive atelectasis), and depression of the ipsilateralhemidiaphragm. The ipsilateral lung can be seen outlinedby a sharp white line of visceral pleura separated fromthe chest wall by radiolucent pleural space devoid of lungmark ings . 1 In th is case, no radiological sign ofpneumothorax is noted in the relatively more radiolucentright hemithorax to account for the left mediastinal shift.The diagnosis of pneumothorax can be excluded.

Left lower lobe collapse

In left lower lobe collapse, radiographic signs of leftlung volume loss will be similar to that of left upper lobecollapse except for left tracheal shift which is morecommonly associated with the latter. On the frontalradiograph, left lower lobe collapse does not give rise to

veil-like opacity described in left upper lobe collapse, butappears as a triangular opacity behind the heart. Thelateral border of this triangular opacity is formed by theoblique f i ssure which appears sharp as it movesposteriorly and inferomedially,' and becoming tangentialto the x-ray beam. The apex of the triangular opacitypoints to the left hilum which is usually depressed androtated medially. The descending thoracic aorta and partsof the hemidiaphragm which are normally outlined by theaerated lung are si lhouetted by the left lower lobecollapse. In contrast, the aortic knuckle , which isrelatively far away, remains sharply outlined by air in theleft upper lobe. Occasionally, left lower lobe collapse canbe obscured by the heart shadow and a penetrated frontalview would be useful to confirm this diagnosis. Althoughthere is loss of left lung volume, the other radiographicfeatures are typical of left upper lobe collapse which aredistinct from that of left lower lobe collapse.

Progressive massive fibrosis

This is a complication of pneumoconiosis (e.g.silicosis). There is rapid development of massive, ill-defined, dense, oval or round shadows which are bilateraland symmetrical in the upper two-thirds of the lungs.These changes are superimposed on background of smallnodules of pneumoconiosis. The absence of thesefeatures in this case excludes the diagnosis. •

References

Rubens MB. The pleura - collapse and consolidation. In: Sutton D (ed).

A Textbook of Radiology and Imaging. 5th ed. Churchill Livingstone, New

York, 1992;pp371-372,379-389.

Reed JC. Chest Radiology: Plain Film Patterns and Differential Diagnoses.

3rd ed. Mosby Year Book, St Louis, 1991;ppl67-194,209-228.

Chapman S, Nakielny R. Aids to Radiological Differential Diagnosis. 3rd

ed. London: W.B. Saunders. 1995;pp110-118.

Wilson AG. 1) Interpreting the Chest Radiograph. 2) Large Airway

Obstruction. In: Grainger RG, Allison DJ (eds). Diagnostic Radiology.

2nd ed. Churchill Livingstone, Edinburgh, 1992;pp150-151,254-255.

517