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SURGICAL PATHOLOGY OF HYDATIDCYSTS OF THE LUNG

By C. J. OFFICER BROWN, M.D., F.R.C.S., F.R.A.C.S.Consulting Thloracic Surgeon, Alfred Hospital, .M1elbourne

A hydatid cyst in the lung starts with thelodgment of the hexacanth embryo of Echinococcusgranulosus in the interstitial tissue of the lung, anda small, progressively growing cyst develops. Therate of growth varies but quite large cysts may beseen in children of two or three years old, or inimmigrants, who have only been in Australia for ashort period and who had clear X-rays on arrival.Around the cyst a fibrous adventitial capsule is

formed and, as it enlarges, it compresses alveoliand impinges on blood vessels and bronchi. Bloodvessels are eroded and this explains the frequencyof haemoptyses as a symptom of hydatid diseaseof the lungs. Bronchi are also eroded and openinto the adventitiae and, consequently, when thecyst is collapsed or removed there is almost alwaysa bronchial communication with its bed and, whenrupture occurs into the pleural cavity, a pneumo-thorax is almost certain to follow and may developtension. In my experience every cyst has beensomewhere in contact with visceral pleura. Thismay be on the diaphragmatic surface or the medias-tinal surface or in a fissure, but, in consequence ofthis relationship, they can all be removed withoutcutting air-containing lung. Because the costalsurface is so much greater than the other surfacesof the lung, the majority of cysts will be foundsomewhere in contact with the chest wall.

During the last 20 years 152 patients have beenoperated upon in the Alfred Hospital for hydatiddisease of the lungs and pleura: 173 operationswere done to remove i86 cysts, or their results,from the thoracic cavity and seven from the liver.All the operations were carried out by myself orMr. Kenneth Morris, who has worked with me illthe Surgical Thoracic Unit for the last eight years.No patient died as a result of operation. In sixpatients with post-hydatid cavities and in one witha large degenerated calcified cyst the diagnosis wasnot confirmed by the recovery of hydatid materialat operation, but in all these patients the pasthistory of causative hydatid disease was unequi-vocal, in every other patient hydatid disease wasproved at operation.

In Table i, the total number of cysts and patientshas been listed. In 68 patients all the cysts weresimple and unruptured. The total of such cystsremoved was 85, but some of these occurred in thelungs of 66 patients of Group 2, who all had atleast one cyst ruptured into a bronchus. In these66 patients, a total of 76 cysts had undergone intra-bronchial rupture. In seven patients pulmonarycysts were complicated by intrapleural rupture atthe time of operation, and in three patients livercysts had ruptured into the pleura, and in one aliver cyst had ruptured into a bronchus. Fourpatients had extrapleural cysts in the chest wall andone of these had extended into the spinal canal,causing paraplegia, and one had a degeneratedcyst in the diaphragm. Two patients were seenfor the first time with recurrent pleural cysts, andthree patients, from whom simple cysts had beenremoved, returned for a second operation for re-current cysts of the pleura. No patient has beenincluded twice in Table i, but every cyst removedhas been tabulated. Nine patients had bilateralcysts and two operations were done in eight ofthem. In the last patient, two cysts in the rightlung and one in the left were removed at the sameoperation.

Although a cyst may remain simple for manyyears and may grow to occupy the greater part of apleural cavity, the majority sooner or later ruptureinto a bronchus, and in this series more than halfthe cysts had ruptured in this way before they wererecognized. Usually the rupture floods the broni-chial tree with fluid, and blood and fluid arecoughed up with great distress to the patient, butit may be quite silent and many patients, whopresent with collapsed cysts, have no idea when thefluid was evacuated. Usually the membrane isretained within the adventitial cavity but occasion-ally it is evacuated in one piece and patients havebeen suffocated by impaction of the membrane inthe larynx. Immediately after rupture an X-raypicture of the lungs shows a typical appearance.The cyst is represented by an air-containing spacewith a fluid level and membrane showing irregu-

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I96 POSTGRADUATE MEDICAL JOURNAL April 1i958

TABLE IHYDATID DISEASE OF LUN(;S ANI) PLEURA

SUMMARY OF 152 PATIENTS WxITH NO MORTALnITTotal

Classification Right Left Cysts I'atients

I. Simple Cyst of Lung .. .. .. .. .. .. .. 53 32 5 68

2. Ruptured Lung Cysts:(a) Into Bronchus:

Pneumocyst .. .. .. .. .. .. .. I I I

Retained menbrane .. .. .. .. .. .. 28 I6 44 38Suppurating 1.. .. .. .. .. .. I4 5 9g i8Degenerated calcified cyst .. .. .. .. .. 3 3 3Post-hvdatid cavity .. .. .. .. .. .. 6 3 9 6

Totals .. .. .. .. .. .. .. .. .. .. 5I 25 76 66

(b) Into Pleural Cavity:Hvdatid pheumothorax .. .. .. .. .. .. I I IChronic hydatid hydrothorax .. .I. .. . ..IHydatid pyo-pneumothorax .. .. .. .. .. 2 2 2Secondary pleural echinococcosis. .. ... I I IHydrothorax absorbed leaving sub-pleural retained menibrane I I IPyothorax with general peritonitis I 2I I

Totals . .. .. . .. .. . .. .. ..5 2 7 7

3. Subphrenic Liver Cyst ruptured into pleural cavity .. .. .. 3 3 3

4. Subphrenic Liver Cyst ruptured into bronchus .. .. .. ..

5. Extrapleural Cyst .. .. .. .. .. .. .. .. 2 2 4 4

6. Degenerated Cyst of diaphragm .. .. .. .. .. ..

7. Recurrent Pleural Cysts:(a) Developed from scolices .. .. .. .. .. .. 2 3 5 I(b) Developed from daughter cysts .. .. .. .. .. I I

Totals .. .. .. .. .. .. .. .. . . . . ii8 65 183 152

.. ......... .. .... ..... ..

FI(. i .-Cyst of the lingulai, itter' intrabronchialrupture, showing air-containing pneumocystNwith fluid level and crumpled membrane float-ing above the fluid.

larly above the fluid (Fig. i). Air may be trappedin the space and the tension cyst may requireurgent decompression. If nothing is done at thisstage, the fluid and air usually disappear and theadventitia shrinks down on the crumpling mem-brane and an opaque shadow, much smaller thanthe original cyst, remains in the X-ray. Unlessthe history of rupture is clean-cut or immunologi-cal tests are positive, diagnosis from other lumpsin the lung is often impossible. This stage maypersist for many years causing no symptoms.Occasionally daughter cysts will develop amongstthe crumpling membrane and this is the only cir-cumstance in which I have seen them in lung cysts.'lTheir rarity suggests that, in most cases, the upsetof rupture anld evacuation devitalizes the cyst. De-generation of the membrane and calcification mayoccur and again, I believe, this is the only cir-cumstance in which calcification is seen in hydatidcysts in the lung.

Suppurationi may complicate the picture afterrupture and may commence either in the pneumo-cyst stage or in the stage of retained membrane.Usually it is an indolent infection contained withinthe adventitia, resulting in cough with expectora-

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April 1i958 OFFICER BROWN: Surgical Patliology of J'ydaltid (vAsts of th111/iLiii 197

FIG. 2.-Bronchograim showing post-h.vdatid cavit!left after the removal of a lar-ge suppurating cyst.Note several hronchi running into cavity.Patient was suLffe-ing fl-rom1 frequent haeniop-tvsCs.

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Fi(,. 3.-Respiratory epitheliuni lining post-hydatidcavitY.

2.)

I

9

FmG. 4. --l'ost-hydatid cavity laid open.

tioin, anid the inembranie may gradually disintegrateand be coughed up, but it is surprising how normal

a membranie may remalln, even atter it has beeibathed in pus for several years.

After the final evacuation of the cyst, the ad-ventitial cavity shrinks down and may obliterate,but in many cases a pocket, demonstrable bybronchography, persists and this is more likely tobe seen when evacuation after rupture has beendelayed and accompanied by suppuration (Fig. 2).'I'hese cavities become lined by respiratory-typeepithelium (Fig. 3), although there may be someareas without epithelium, and some areas arecovered with squamous cells, and they have severalbronchi opening into them (Fig. 4). They may bequite symptomless or may cause repeated haemop-tyses or may become intermittently or chronicallyinfected.

'The result after operative removal of a cyst isthe same as that following spontaneous rupture,and a post-hydatid cavity may persist but, if a cystthat is not suppurating is cleanly removed andthere is no prolonged infection in the space afteroperationi, troublesome post-hydatid cavities arerarely seeni.

In some cases suppuration extends beyond theadventitial space, and some segments or a lobe maydevelop the changes of chronic pulmonary sup-puration and bronchiectasis similar to those seenwith other retained foreigin bodies (Fig. 5).

In a smaller proportion of patients the cyst rup-tures into the pleural cavity. Intrabronchial spillwATith cough and expectoration may occur at the

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198 POST'GRADUA'TE M\IEDICAL JOURNAL April 1958

::........

FI(;. 5.-Bronchiectasis following removal of asuppurating cyst in the lingula. Patienitsuffered fronm repeated haenioptNses.

same time, or the onset may be similar to that ofother spontaneous pneumothoraces. The fluidempties into the pleural cavity and air escapes, apneumothorax develops and may develop tension.'The membranie may remain within the adventitiaor may be expelled into the pleural cavity. Ineither case the rupture may seal and the air atndfluid be absorbed. If the membrane is still withinthe adventitia, wvhen the lung re-expands, thepicture is that of retained membrane followingintrabronchial rupture, but, in addition, secondarypleural cysts may develop from spilled scolices.

In two of my patients, the air leak closed afterthe membrane had escaped into the pleural cavityanid, in one, a chroinic hydrothorax without fistulapersisted until the membrane was removed and thelung decorticated. hI the other the lung re-expainded anid the mnemnbralnc was eiicapsulated illa small pleurla-l pocket.

SuLppuration may occur aniid the patienit maypresenit with a pyopneumothorax. One of mypatients was seen after intrabronchial rupture ofhis cyst with a typical pneumocyst. Operation wasadvised but he elected to delay and hoped for aspontaneous cure. Six weeks later he developedperitonitis. No cause for the peritonitis was foundin his abdomen at laparotomy, but it was thenrecognized that he had a large pyothorax and

...........

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............

Fi(c. 6.-Rupture of cyst into pleural cavity withhydatid pneumothorax and secondarv pleuralechinococcus. Note multiple small cysts studdedover parietal pleira. Rupture had occuirred sixnionths earlier.

prompt recovery followed evacuation of the pyo-thorax and removal of his cyst.

Secondary pleural Echinococcus (Fig. 6) resultsfrom the development of cysts in the pleural cavityfollowing the spilling of scolices. It is rare andfollows only a small proportion of intrapleural rup-tures. Although millions of scolices are spilled insuch a rupture, only a very few, if any, secondarycysts develop and even where scolices were reck-lessly spilled at operation, as was done by manyAustralian surgeons before the development ofmodern techniques, very few patients presentedwith recurrent pleural cysts.

Because the lung cysts which rupture into thepleural cavity are always simple without daughtercysts, the problem of intrapleural spilling is quitedifferent to that of intraperitoneal spilling fromliver cysts containing daughter cysts and broodicapsules in large numbers. In one patient of m)yseries, operated on primarily by aniother surgeon,daughter cysts wvere present, presumably in apreviously ruptured and collapsed cyst, and it wasassumed that the escape of one or more of these atoperation was responsible for the development of alocalized posterior pleural pocket stuffed with smallcysts and debris, which I evacuated iS years later.

Liver cysts may rupture through the diaphragminto the pleural cavity and may result in a hydro-thorax which will usually contain bile and daughter

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April I958 OFFICER BROWN: Surgical Pathology of Hydatid Cysts of the Lung

cysts. Where the lung is adherent at the time ofrupture, a broncho-biliary fistula will result, andthis is the commonest cause of this condition inAustralia. Sometimes no bile is expectorated but,even in its absence, the expectoration of daughtercysts should always suggest a primary liver cystwith a bronchohepatic fistula, because daughtercysts are so rare in pulmonary hydatids.

Hydatid cysts may occur in any part of the bodyand we have seen three lying extrapleurally againstthe spine. Cysts in this position are importantbecause they tend to rupture and extend extra-pleurally with the production of multiple daughtercysts and, following a line of least resistance, mayspread through a spinal foramen causing hydatidparaplegia, as had occurred in one of my patients.

Cysts of the diaphragm are occasionally reportedand one, in a degenerated condition when it wasremoved at operation, is included in this series.

Extrathoracic CystsFour of these patients had previously been

operated on for the removal of liver cysts and weremoved liver cysts from seven more of them. One

child had a cerebral cyst and a pelvic cyst re-moved, and had a cyst in the liver and-one in thelung. We removed the large lung cyst, because itseemed likely to rupture, but did not operate onthe liver cyst. He has since died as a result of therecurrence of the cerebral cyst. Although it isgenerally held that the liver is the commonest sitefor hydatid disease in man, Clunies Ross", 2 foundthat lung cysts were more common in sheep.andcattle, and I suspect that the figures relating toman may be fallacious, because in the past manylung cysts were evacuated spontaneously and notdiagnosed. Since the introduction of routinechest radiography, many more lung cysts havebeen found and quite a proportion of the casesincluded in this series presented with symptomlesslumps, and many of them would have gone throughlife unrecognized if it had not been for the X-ray.

REFERENCES1. ROSS, I. CLUNIES (I926), Med. Y. Aust., I, 96.2. ROSS, I. CLUNIES (1929), 'Observation of the Hydatid

Parasite,' Commonwealth of Australian Council of Scientificand Industrial Research, Bulletin No. 40, Melbourne.

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INTRODUCTORY UNUSUAL MANIFESTATIONSMaurice Davidson, D.M., F.R.C.P. J. Smart, M.D., F.R.C.P.

TIHE INCIDENCE AND AETIOLOGY OF CYTOLOGICAL EXAMINATION OF THEPRIMARY CARCINOMA OF THE LUNG SPUTUM AND. PLEURAL EFFUSIONC. E. Drew, M.V.O., F.R.C.S. J. L. Pinniger, D.M., M.R.C.P.

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