subpulmonar pneumothorax

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1978, British Journal of Radiology, 51 , 494-497

Subpulmonary pneumothoraxBy A. S chulm an, M.R.C.P., F.R.C.R., and R. B. Da lrymple, M.B., Ch .B., D.M.R.D., F.F.RAD(D) (S.A .)Departments of Radiology, Groote Schuur Hospital and University of Cape Town, South Africa{Received October, 1977 and in revised form Feb ruary, 1978)

ABSTRACTSeven cases of subpulmonary pneumothorax are pre-sented : four due to penetrating injury, two to blunt traumaand one to osteosarcoma metastasis.The typical and diagnostic appearance is a basal band ofradiolucency bounded above by the thin hair-line of visceralpleura paralleling the dome of the hemi-diaphragm. Whenpartially clotted blood is also present, the appearancebecomes less typical and has to be differentiated fromtraumatic diaphragmatic herniation of bowel and fromtraumatic pneumatocoele by barium studies and by decu-bitus radiographs respectively.It is the bridge-like disposition of the pleural cavitybetween the dom e of the hemi-diaphragm and the hollowedconcavity of the lung base which allows pneumothorax tocollect in it. It is rarely seen because blebs and bullae whichare the commonest causes of pneumothorax are most oftenlocated in the upper zones.A recent report of four cases of subpulmonarypneumothorax (Christensen and Dietz, 1976) stres-sed the importance of pleural adhesions in the upperpleural space causing the pneumothorax to localizein a basal position. We wish to emphasize that sub-pulmonary pneumothorax can probably occur with-out pleural adhesions, that it may be especiallycommon with basal penetrating trauma and that thethoracic bases and not simply the apices must bediligently searched for early small pneu mo thoraces .

MATERIALS AND METHODSDuring a recent period of eight months, we haveseen seven cases of pneumothorax presenting in-itially in an entirely subpu lmo nary situation. Fo ur ofthem were due to penetrating stab wounds of theleft lower chest, two to blunt assault on the left sideof the chest w ithout rad iographic or clinical evidenceof fractured ribs, and one to pulmonary metastasesfrom a femoral osteosarcoma.One patient had treated, healed tuberculosis inboth upper lobes, but none of the others hadclinical or radiographic evidence of pre-existing lungor pleural disease.In five cases, at least some of the subpulmonaryair later moved into more common sites, lateral ormedial to the lung and even eventually up to theapex; this occurred after lying the pa tient on his sidefor decubitus radiographs or simply with the passageof 24 to 48 hours.In five cases, the subpulmonary pneumothoraxshowed the typical appearance, i.e. a band of radio-

lucency without septa or lung markings parallelingthe upper surface of the hemi-diaphragm and sep-arated from the lung by a thin h air-line representingthe basal visceral pleura (Figs. 1-3).Two cases, due to penetrating and blunt traumarespectively, were atypical presumably due to theadditional presence of blood in the pleural space. In

(A) Erect P.A. film.

(B ) Erect lateral film.FIG. 1. Case 1.A 26-year old man received two stab wounds in posterioraspect of left hemithorax causing small subpulmonarypneumothorax. See line of visceral pleura (arrow-heads).Later the same day, a repeat film showed that the air hadmoved to the apex.

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FIG. 2. Case 2.Erect P.A. film. A 31-year old man stabbed in back of lefthemithorax causing small subpulmonary pneumothorax.Paralleling upper surface of diaphragm is the thin line ofvisceral pleura (arrows).

FIG. 3. Case 3.Erect P.A. film. A 17-year old boy seven months afteramputation for femoral osteosarcoma. The pneumothoraxon the left is purely subpulmonary (white triangles), that onthe right is all around the lung. Whole lung tomographyconfirmed that the opacity at the left base (arrow-heads) wasa metastasis projecting inwards from the visceral pleura andthat there were multiple metastases in both lungs ; proven bythoracotomy and histology.

one, the blood and air formed a rounded collectionwith a fluid level above the stomach bubble (Figs.4A & B). Barium examination of the stomach wasentirely normal, while decubitus radiographs showedthat the gas moved freely within the pleural space,

FIG. 4. Case 4.A 25-year old woman received four stab wounds in back ofchest inflicted with screwdriver. In A and B, note the air-fluidcollection (straight black arrows) at the left base above thestomach bubble (arrow-heads). Diagnosissubpulmonaryhaemopneumothorax?, traumatic pneumatocoele?, trau-matic hernia? Barium meal showed no gastric herniation.Decubitus film (c) shows the air moving freely upwards inthe pleural cavity (open arrows) and the blood freely down-wards (curved arrows). Diagnosissubpulmonary haemo-pneumothorax.495

^Bfapi(c) Left lateral decubitus film with barium in stomach.


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thus excluding both traumatic herniation of the gas-tric fundus and traumatic pneumatocoele (Fig. 4c).In the other case (Fig. 5), the air collection at thebase was crossed by numerous septa causing it to re-semble bowel. Again, traumatic herniation was con-sidered but barium examinations of stomach andcolon were normal. Following drainage of the sub-pulmonary pneumothorax, chest radiographs werenormal.The patient with osteosarcoma metastases hadbeen treated by amp utation, radio-therapy and cyto-toxic drugs. Routine chest radiographs were normaluntil seven months after amputation when, althoughthe patient was asymptomatic, there were bilateralpneumothoraces and pulmonary metastases on the

FIG. 5. Case 5.Erect PA film, left basal detail. A 24-year old man wasassaulted receiving blunt skull and facial injuries withamnesia. No clinical or radiographic evidence of fracturedribs but this multi-septate air collection appeared at the leftbase. Contrast studies of stomach, jejunum and colon werenormal, excluding traumatic herniation. Following basalpleural aspiration, chest radiographs became normal. Diag-nosissubpulmonary haemopneumothorax.

visceral pleura (Fig. 3). The right sided pneumo-thorax encircled the lung while that on the left sidewas purely subpulm onary.DISCUSSIONRadiologists are trained to look meticulously at theapices for the earliest evidence of small pneumo-thorax, and recent text books (Fraser and Pare,1970; Crofton and Douglas, 1975; Harris andHarris, 1975) make no mention of pneumothoraxlocated in the initial stages below the lung base evenin erect patients. Our series indicates that, especiallyin cases of penetrating traum a, one should look mostcarefully for the fine hair-line of visceral pleurapushed upwards from the hemi-diaphragm by a

subpulmonary pneumothorax.It is presumably the bridge-like disposition of thepleural space between the dome of the hemi-diaphragm and the hollowed out base of the lungthat allows pneumothorax, arising from injury ordisease of this p art of the lung , to collect here . Part ofthe reason why this is seen so seldom is that themajor causes of pneumothorax, i.e. pleural blebs andemphysematous bullae, are situated most commonlyin the uppe r parts (Crofton and D ouglas, 1975).Neonatal pneumomediastinum is occasionally as-sociated with air loculated below the lung and this isthought to be extra-pleural, between the parietalpleura and the hemi-diaphragm (Lillard and Allen,1965; Caffey, 1972). However, none of our patientshad pneumomediastinum and in five of them, someor all of the subp ulmo nary air later moved into m oretypical intrapleural sites around or above the lungafter some time or after lying the patient on his sidefor decubitus radiographs. Indeed, it would bedifficult for air to track far beneath the parietalpleura as it is found to be firmly adherent to under-lying tissue during thoracic surgical dissections.It is also unnecessary to postulate the presence ofpleural adhesions higher up causing a subpulmonarysituation (Christensen and Dietz, 1976) as in six ofour cases there was nothing to suggest previouspulmonary or pleural disease and again because ofthe later movement of some of the air into higherparts of the pleural space.The typical appearance of subpulmonary pneu-mothorax is a radiolucent zone without bronchovas-cular markings or septa lying on the hemi-diaphragmand bounded above by the thin hair-line of thevisceral pleura paralleling the dome of the hemi-diaphragm (Figs. 1-3). This appearance should bediagnostic but can be confirmed by the free move-ment of the air into other parts of the pleural spaceafter lying the patient on his side.

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A subpulmonary pneum othorax crossed by strandsof partially clotted blood producing a multiseptateappearance (Fig. 5) can resemble basal bullae or thefold or haustral pattern of bowel herniated through adiaphragmatic laceration. The latter is easily ex-cluded by barium study of stomach and colon(Fataar and Schulman, 1978). If the blood producesa fluid level w ithin the loculated air (Figs. 4A and B)it can again resemble traumatic herniation as well astraumatic pneumatocoele (Fagan and Swischuk,1976; Freed, 1977) but decubitus radiographs showindependent movement of the air upward and theblood downward to opposite extremities of thepleural space thus proving that the collection isintrapleural and not intrapulmonary.The visceral pleura is much thinner than thehemi-diaphragm so that subpulmonary air shouldnot be m istaken for subdiaphragmatic air.We are unable to account for the fact that allseven of our cases were left sided. It can be arguedthat when facing a right handed assailant, the leftside of the chest is more likely to receive the stabwound. However, in three of the four cases of stabwound s, they were in fact in the back of the chest.Pulmonary metastases are a known cause of pneu-mothorax which for obvious reasons may be bilateral(Janetos and Ochner, 1963; Wright, 1976; Winter,1976; Kai-Yui Yeung and Bonnet, 1977). Themajority of published cases have been due to sar-comas of various origins, the commonest beingosteosarcoma and most frequently in children andadolescents. Subpulmonary pneumothorax has notbeen reported.Our two cases due to blunt trauma had a pneu-mothorax in spite of no evidence of rib fracture orpenetrating injury. The presence of rib fractures is

underestimated by radiological examination but evenin the absence of fractures, blunt trauma can pro-duce both lung damage and pneumothorax (Gerblichand Kleinerman, 1977).REFERENCESCAFFEY, J., 1972. Pediatric x-ray d iagnosis, Vol. I, 6th edn.pp . 431-434 (Year Book Medical Publishers).CHRISTENSEN, E. E., and DIETZ, G. W., 1976. Subpulmonicpneumothorax in patients with chronic obstructive pul-monary disease. Radiology, 121, 3337.CROFTON, J., and DOUGLAS, A., 1975. Respiratory diseases,2nd edn. pp. 350-359 and 478-487 (Blackwell ScientificPublications, Oxford).FAGAN, C. J., and SWISCHUK, L. E., 1976. Traumatic lungand para-mediastinal pneumatocoeles. Radiology, 120,11-18.FATAAR, S., and SCHULMAN, A., 1978. The diagnosis ofdiaphragmatic tears. British Journal of Radiology (inpress).FRASER, R. G., and PARE, J. A. P., 1970. Diagnosis of diseasesof the chest, Vol. 1, pp. 371-376 (W . B. Saunders Company,Philadelphia).FREED, C , 1977. Traumatic lung cysts after penetratingchest injury (report of three cases). South African MedicalJournal, 51,720-722.GERBLICH, A. A., and KLEINERMAN, J., 1977. Blunt chesttrauma and the lung (editorial). American Review ofRespiratory Diseases, 115, 369-371.HARRIS, J. H., and HARRIS, W. H., 1975. The radiology ofemergency medicine, pp. 226-230. (Williams and Wilkins,Baltimore).JANETOS, G. P., and OCHNER, S. F., 1963. Bilateral pneu-mothorax in metastatic osteogenic sarcoma. AmericanReview of Respiratory Diseases, 88, 73-76.

KAI-YUI YEUNG and BONNET, J. D., 1977. Spontaneouspneumothorax with metastatic malignant melanoma.Chest, 71, 435-436.LILLARD, R. L., and ALLEN, R. P., 1965. The extrapleuralair sign in pneumomediastinum. Radiology, 85, 1093-1098.WINTER, W. G., 1976. Spontaneous pneum othorax heraldingmetastasis of adamantinoma of tibia. The Journal of Boneand Joint Surgery (American Volume), 52, 416-417.WRIGHT, F. W., 1976. Spontaneous pneumothorax andpulmonary malignant diseasea syndrome sometimesassociated with cavitating tumours. Clinical Radiology, 27,211-222.

Book reviewComputerised cranial tomography. Edited by B. Felson,pp . 146, illus., 1977 (New York; Grune and Stratton Inc.)$18.5O/13-15.This book presents a collection of papers which wereoriginally published in seminar in Radiolgoy Vol. 12. Eachof the major papers is a good, well illustrated review of itssubject. The presentation on equipment and physics byTor-Pogossian stands o ut as a model of clarity in explainingthis difficult field to diagnostic radiologists.This book is not meant to be comprehensive and the re areobvious omissions as for example, the lack of considerationof hydrocephalus or the effects of surgery and other therapy.The defects are covered to some extent in the good selectionof references.It is recommended as an authorative introduction tocranial computed tomog raphy. B. E. KENDALL.

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subpulmonar pneumothorax

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