Thorax: first published as 10.1136/thx.8.3.189 on 1 September 1953. Downloaded from

Thorax (1953), 8, 189.

THE SURGICAL ANATOMY OF THE PULMONARY VESSELS BY J. C. VAN DER SPUY From the Thoracic Surgical Unit, Johannesburg Group of Hospitals, and Department of Surgery, University of the Witwatersrand, South Africa

(RECEIVED FOR PUBLICATION SEPTEMBER 29, 1952)

Surgical resections of the lung have in recent diately beneath the pleura, or deeply, in an inter- years become common and relatively safe pro- segmental plane. The intersegmental veins drain cedures. Depending upon the extent and nature of also adjacent segments within a lobe and may the disease process, the whole lung, one or two drain adjoining segments of a different lobe. In lobes, or one or more bronchopulmonary segments the latter instance the veins pass subpleurally may require excision. Modern pulmonary re- across the base of a fissure. The perisegmental section depends to a very large extent upon the (intersegmental or segmental) veins course some- precise identification of the primary, secondary, what independently of the segmental bronchi and and tertiary hilar bronchovascular structures, and arteries to reach the subp'eural plane in the it has thus become essential to have a detailed primary hilum and there join a main pulmonary knowledge of the anatomy of these structures at vein. the different hilar levels. PULMONARY ARTERY The aim of this paper is to describe and to illus- The main pulmonary artery divides in front of copyright. trate this anatomy. It is based upon a study of 42 the left main bronchus into a left and a right pul- complete casts of the bronchovascular tree and the hilar anatomical findings displayed during the monary artery (Fig. I). course of 92 partial and 30 whole lung resections RIGHT PULMONARY ARTERY.-The right pul- performed by some members of the Thoracic monary artery has to cross the midline to reach the Surgical Unit, Johannesburg, during the past year. root of the right lung. This it does by passing http://thorax.bmj.com/ The pulmonary vessels and the bronchi are illus- transversely to the right, behind the ascending trated chiefly from such approaches as are used aorta and the superior vena cava respectively, in by the surgeon when dissecting the different front of the oesophagus and immediately above primary, secondary, and tertiary hila. the left atrium and right superior pulmonary vein Each lung, anatomically, is composed of 10 under cover of the arch of the azygos vein. bronchovascular or bronchopulmonary segments. Behind the superior vena cava the right pul- These segments are miniature lobes differing from monary artery divides into an upper and a lower lobes only in their size and in the usual absence of trunk (Fig. I). Of these the superior pulmonary fissures at their anatomical boundaries. trunk supplies the anterior and apical broncho- on September 28, 2021 by guest. Protected A lobar bronchus branches from a main pulmonary segments of the right upper lobe by bronchus at a relatively constant site, and sub- dividing, as it enters the lung substance in front of divides in a more or less standard fashion into its the right upper lobe bronchus, into the apical (Al) segmental bronchi. The pulmonary artery, how- and anterior (A3) segmental arteries (Fig. II). ever, has not this same lobar distribution, and Emerging from behind the superior vena cava, it although the segmental pulmonary arteries follow is, but for the covering given it by the pleura on the segmental bronchi somewhat closely, they tend the root of the lung, completely exposed. to have a variable and independent origin from the The inferior pulmonary trunk proceeds from pulmonary artery. behind the superior vena cava to become sub- The segmental artery, like the segmenital pleural, but only to disappear almost immediately bronichus, occupies a central position within the by passing behind the superior pulmonary vein bronchopulmonary segment. The blood carried (Fig. IV). It is the counterpart of the left pul- to the segment by such a centrally situated artery monary artery. Passing laterally and slightly is collected by perisegmental pulmonary veins; as downwards, under cover of the superior pul- such, they are either placed superficially, imme- monary vein (Fig. IV), it crosses, the anterior sur- Thorax: first published as 10.1136/thx.8.3.189 on 1 September 1953. Downloaded from

190 J. C. VAN DER SPUY face of the right bronchus, between the origins of Arising from the inferior pulmonary trunk, the upper and middle lobe bronchi (Figs. II and slightly above the lower lobe apical segmental III). Then curving downwards, it runs sub- artery, is the artery to the posterior segment of pleurally in the depths of the oblique fissure (Fig. the upper lobe. It passes backwards and upwards III), on the antero-lateral aspect of the basal and is termed the posterior ascending artery (A2, bronchus. Figs. III, Illa, and IVd). Whereas the posterior The inferior pulmonary trunk supplies the segmental artery of the right upper lobe in the majority of cases arises from the pulmonary middle and lower lobes as also, in the majority artery in this situation, it frequently, however, of cases, the posterior bronchopulmonary seg- arises from the superior pulmonary trunk itself ment of the upper lobe via the posterior ascend- of ing segmental artery (A2, Fig. III) and frequently during the latter's subpleural course, from either segment, via its two terminal branches, namely, the apical (Al) also the anterior bronchopulmonary and the anterior ascending segmental artery (A3, Fig. or anterior (A3) segmental arteries (Figs. Ila from the lower lobe apical segmental artery such instances the anterior ascending seg- Ilb), III). In (A2, Fig. IlIb), or even from the middle lobe mental artery is usually accessory to the anterior artery. segmental artery (A3, Fig. II), but in a small per- centage of these cases it is solely responsible for The inferior pulmonary trunk breaks up into supplying the anterior bronchopulmonary seg- the four basal segmental arteries, either just within ment. Occasionally, however, the anterior ascend- the oblique fissure or just inside the lung ing segmental artery may derive its origin from parenchyma. Each basal segmental artery follows the middle lobe artery (A3, Fig. IlIb). its respective bronchus very closely, keeping to its antero-l1teral side. These take off from the The acute angle formed between the oblique inferior pulmonary trunk either singly or via an and transverse fissures forms the point of an anterior and a posterior trunk, the former dividing arrow which guides one to that area of the sub- into the medial (A7) and anterior (A8) basal seg- pleural pulmonary artery, in the depths of the mental arteries, whereas the latter provides thecopyright. oblique fissure, from which the pulmonary arterial lateral (A9) and posterior (AIO) basal segmental supply to the middle and lower lobes and part of arteries (Fig. ILL). the upper lobe is derived (Fig. III). LEFT PULMONARY ARTERY.-The left pulmonary Arising from the postero-lateral surface of the artery, arising in front of the left main bronchus, inferior pulmonary trunk, in this area, one finds ascends slightly in a posterior and lateral direc- the lower lobe apical segmental artery (A6, Fig. tion, arches over the left main bronchus, and then http://thorax.bmj.com/ III). It descends slightly in a backward direction, hooks round the left upper lobe bronchus, follow- lying superior and, as the surgeon sees it, lateral ing a subpleural course throughout (Figs. V, VI, to its corresponding bronchus. To the anatomist, and VII). It more fully establishes its superiority however, the artery is superior and anterior to the over the left superior pulmonary vein (Fig. VIII) bronchus. The reason for this difference is that than does its right counterpart, the inferior pul- the surgeon, in opening the slit-like oblique fissure, monary trunk, which lies directly behind the right displaces the apex of the lower lobe medially. superior pulmonaty vein (Fig. IV). Similarly also, the middle lobe artery (Figs. III, Owing to the different courses taken by the left on September 28, 2021 by guest. Protected IIIa, and IIIb) appears to be superior and lateral and right pulmonary arteries, the antero-posterior to its corresponding bronchus instead of superior and infero-superior relations in the hilum of the and posterior. left lung are vein, bronchus, and artery, whereas The lower lobe apical segmental artery is the same relations in the hilum of the right lung usually single (A6, Fig. III), but at times the apical are vein, artery, and bronchus. segment of the lower lobe summons the aid of a As the left pulmonary artery is about to arch second segmental artery (A6 i, A6 ii, Fig. IIIa). over the left main bronchus it gives off the first of Arising more or less opposite the lower lobe a set ies of segmental arteries for the supply of the apical segmental artery, from the anterior surface left upper lobe. This segmental artery (A3, Fig. of the pulmonary artery, is the middle lobe artery. V), arising from the antero-superior surface of the It may be single, when it divides into two pulmonary artery, passes in front of the upper branches, one each for the medial and lateral seg- division of the left upper lobe bronchus to the ments of the middle lobe (A4 5, Fig. Illa). As anterior bronchopulmonary segment, crossing frequently two separate middle lobe segmental behind the apical-posterior tributary (VI, V2, Fig. arteries are present (A4, A5, Fig. III). VIII) of the superior pulmonary vein. Thorax: first published as 10.1136/thx.8.3.189 on 1 September 1953. Downloaded from

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192 J. C. VAN DER SPUY From the postero-superior surface of the left The lingular artery, on the other hand, may pulmonary artery the short, sessile, bifurcating form with the anterior segmental artery a com- apical-posterior segmental artery (Al, A2, Fig. VI) mon antero-lingular trunk on the antero-superior is derived. The apical-posterior artery may, how- surface of the pulmonary artery immediately be- ever, be a clearly defined single trunk, dividing fore it loops over the upper surface of the left into its two constituent segmental arteries (Fig. main bronchus (Fig. Vb), leaving the anterior sur- VIb). On the other hand, the apical segment may face of the pulmonary artery in the lingular region be supplied by two separate segmental arteries (Al, of the oblique fissure conspicuously bare (Fig. Al, Fig. VIa). Similarly, the posterior segment VIIb). Alternatively, only the superior lingular may have a dual segmental arterial supply (A2, segmental artery (A4) may be associated with the A2, Fig. VIc). anterior segmental artery (Fig. Vc), leaving its Arching around the back of the upper lobe partner (A5) in charge of the oblique fissure (Fig. bronchus, the left pulmonary artery enters the VIIc). oblique fissure, and, running immediately beneath The apical segmental artery (Al) also occasion- the pleura, it comes to lie on the side of the lower ally arises with the anterior segmental artery (A3) lobe bronchus. From this position, near the upper from the antero-superior surface of the left pul- end of the oblique fissure, the artery sends from its monary artery (Fig. Vd). anterior aspect a single arterial stem to the lin- To ascertain the whereabouts of these segmental gular bronchopulmonary segments. The lingular vessels it is advisable to display the segmental artery is posterior to its corresponding bronchus arterial anatomy in the lingular region of the (but lateral to it as the surgeon sees it) and at a oblique fissure, should this fissure be fully somewhat lower level, and divides into the developed. Depending on whether there are three, superior and inferior lingular segmental arteries two, one, or no segmental arteries in the lingular (A4+5, Fig. VII). Commonly the lingular seg- area, so there will arise no, one, two, or three mental arteries arise independently from the segmental arteries from the antero-superior sur- anterior surface of the pulmonary artery (A4, A5, face of the pulmonary artery (Figs. VII, VIla, copyright. Fig. VII i). VIIb, VIIc, and Figs. V, Va, Vb, and Vc). The Arising from the postero-lateral surface of the remaining arterial stems arising from the postero- pulmonary artery, more or less opposite the lin- superior or posterior surface of the arching pul- gular artery, although usually at a somewhat monary artery belong to the apical-posterior higher level, is the lower lobe apical segmental bronchopulmonary segment. artery (A6, Fig. VII). As on the right side, here too The four basal segmental arteries follow their http://thorax.bmj.com/ there may be two separate lower lobe apical seg- respective bronchi closely, and, like their fellows mental arteries (A6 i, A6 ii, Fig. VII ii). on the right side, cling to the antero-lateral sides The level of origin of the lower lobe apical seg- of these bronchi (Fig. VII). Here also the pul- mental artery in relation to that of the lingular monary artery may terminate within the oblique artery is of particular importance (Fig. VII). In fissure, but usually the dissection has to be lower lobectomy this segmental artery (A6) re- extended into the lung substance to see that the from the rest of the medial (A7) and anterior (A8) basal segmental quires to be ligated separately like their corresponding bronchi, usually lower lobe artery, as mass ligation of the pul- arteries, on September 28, 2021 by guest. Protected monary artery immediately above the origin of the arise from a common anterior trunk, and that the first segmental artery to the lower lobe (A6) would lateral (A9) and posterior (AIO) basal segmental arterial to the arteries either leave singly or via a common include the segmental supply lingula. posterior trunk (Fig. VII). The anterior segmental artery (A3) commonly arises from the anterior surface of the pulmonary artery in the oblique fissure in relation to the PULMONARY VEINS lingular artery. It may form with the lingular RIGHT SUPERIOR PULMONARY VEIN.-The right artery (A4, A5) a common antero-lingular trunk superior pulmonary vein drains the right upper (Fig. VIla), or it may be associated with only the and middle lobes. On entering the pericardium, upper of two separate lingular segmental arteries this vein lies immediately below the right pul- (Fig. VIIa iii). On the other hand, the anterior monary artery. In the hilum of the lung, how- segmental artery may arise independently of and ever, it overlaps the inferior pulmonary trunk, cranial to a bifurcating lingular artery (Fig. VIla i) and its uppermost tributary, the apical-anterior or two separate lingular segmental arteries (Fig. vein (VI, V3, Fig. IV), descends across the anterior VIIa ii). segmental artery. This subpleural vein drains the Thorax: first published as 10.1136/thx.8.3.189 on 1 September 1953. Downloaded from

THE SURGICAL ANATOMY OF THE PULMONARY VESSELS 193 upper and middle lobes via three to five trunks. said to resemble a shrub (Boyden, 1945), the The uppermost trunk is the apical-anterior branches of which radiate somewhat irregularly vein, which receives a subpleural segmental vein from a short stem (Figs. IV and IVa). Its lower- from each of the apical and anterior broncho- most tributary is the medial basal segmental vein pulmonary segments (VI, V3, Fig. IV). (V7), which lies immediately above a constantly Entering the superior pulmonary vein imme- present lymph gland at the upper end of the pul- diately below the apical-anterior trunk is the monary ligament. inferior vein (+, Fig. IV), so called because it The uppermost, and most easily discernible, courses subpleurally on the inferior surface of the tributary is the lower lobe apical segmental vein, upper lobe (anterior segment) in the transverse which, descending from the apex of the lower fissure. lobe, crosses behind the basal bronchus, below the Next, the tributaries from the lateral and origin of its corresponding bronchus, to end at the medial bronchopulmonary segments of the middle upper angle of the receiving vein somewhat pos- lobe enter the superior pulmonary vein, either as teriorly (V6, Figs. IV and IVa). a common trunk or independently (V4, V5, Fig. The remaining three tributaries, namely, the IV). anterior (V8), lateral (V9), and posterior basal One more vein completes the quintet. This is (V1O) segmental veins, leave their respective inter- the posterior segmental vein. But for the course segmental regions (Fig. IV) by crossing behind of this vein the superior pulmonary vein would their corresponding bronchi to enter the inferior have been a channel shaped like a hand, all the pulmonary vein in no fixed manner between the digits meeting the palm subpleurally. This pos- lower lobe apical segmental vein above and the terior vein (V2, Fig. IV), however, comes from the medial basal segmental xein below. very depths of the upper lobe to enter incon- LEFT SUPERIOR PULMONARY VEIN.-The left spicuously the deep surface of either the pul- superior pulmonary vein is formed by three monary vein itself, or, more commonly, its inferior venous trunks which, to the surgeon, are all copyright. tributary, having first catered for the posterior and antero-inferiorly related to their corresponding intersegmental regions of the upper lobe (V2, Fig. bronchi, and which, anteriorly, are all covered by IVd). This vein is unique in that, of all the seg- the pleura on the root of the lung. It receives all mental veins, it is the only one which at no stage the left upper lobe segmental veins (Fig. VIII). runs a subpleural course. The uppermost tributary is the apical-posterior One or both middle lobe veins may at times trunk, which drains the apical-posterior broncho- http://thorax.bmj.com/ become detached from the superior pulmonary pulmonary segment. This apical-posterior trunk vein to drain into the inferior pulmonary vein (Vl, V2, Fig. VIII) overlies the anterior artery or (Figs. IVb and IVc). Similarly, one or both of the antero-lingular trunk when these arteries arise these middle lobe segmental veins may drain from the antero-superior surface - of the pul- directly into the left atrium. monary artery. RIGHT INFERIOR PULMONARY VEIN.-The right Joining the superior pulmonary vein laterally inferior pulmonary vein, in the root of the lung, and immediately below the apical-posterior vein courses below the right superior pulmonary vein; is the tributary from the anterior segment (V3, on September 28, 2021 by guest. Protected but here it occupies a somewhat more posterior Fig. VIII). Before reaching the superior pul- plane. Its tributaries leave the lung by passing monary vein the anterior segmental vein is joined behind their respective bronchi. For this reason, by the inter-antero-lingular vein (+, Fig. VIII) and also because the inferior pulmonary vein is to which drains along the intersegmental plane de- some extent hidden by the lower lobe and by the scribed by its name, thus corresponding somewhat upward extending anterior layer of the pulmonary to the inferior vein draining into the right superior ligament, the vein and its tributaries are more pulmonary vein. readily dissected from the posterior aspect (Figs. The lowermost member of the left superior pul- IV and IVa). monary vein is that which drains the superior and The inferior pulmonary vein receives all five inferior lingular bronchopulmonary segments (V4, segmental veins which drain the lower lobe, and V5, Fig. VIII). These two segmental veins may, occasionally, as mentioned above, one or both however, join the superior pulmonary vein separ- middle lobe segmental veins. If the superior pul- ately. One or both lingular veins may, like the monary vein may be compared with a hand, then middle lobe veins, empty into the inferior pul- the inferior pulmonary vein can most certainly be monary vein or directly into the left atrium. Q Thorax: first published as 10.1136/thx.8.3.189 on 1 September 1953. Downloaded from

194 J. C. VAN DER SPUY

The apical-anterior-posterior segmental venous structures met with during hilar dissections are of pattern of the left upper lobe may at times prime importance to the surgeon, and the latter resemble that of the right upper lobe and vice term emphasizes the existence of multiple versa. bronchovascular hila. LEFT INFERIOR PULMONARY VEIN.-The left in- The usual anatomy as well as different varieties ferior pulmonary vein runs, like the right inferior of the less usual anatomy, as indicated by big and pulmonary vein, below the superior pulmonary small Roman numerals respectively, are illustrated. vein and at a somewhat more posterior level. By indicating the views from which the anatomy is Similarly, its five tributaries, crossing behind their shown, the models, placed immediately above the respective bronchi, can be dissected more readily illustrations, allow one to become readily orien- from behind. Here too the lower lobe apical seg- tated, and explanatory descriptions are thereby mental vein (V6) and the medial basal segmental considerably reduced. vein (V7) are the uppermost and lowermost tribu- I am extremely grateful to Mr. L. Fatti, Senior taries respectively (Fig. VIII). Surgeon, Thoracic Surgical Unit, Johannesburg Group An inferior pulmonary vein frequently re- of Hospitals, and also to Mr. G. R. Crawshaw, of sembles not a shrub but a branch of a tree (Boy- the same unit, for communicating to me their observa- den, 1945), the thick end of the branch representing tions on the anatomy of the pulmonary vessels in the inferior those resections which I did not personally witness. pulmonary vein, which, tapering down, Of the bronchovascular casts mentioned above, 32 becomes the posterior segmental vein (V10). The were prepared by Dr. F. Frodl, late of the Depart- branch has three lateral branches, namely the ment of Pathology, Utrecht, Holland. His paper on lower lobe apical segmental vein (V6), the anterior the detailed anatomy of the pulmonary vessels is basal vein (V8), and the lateral basal vein (V9) now in the press. I am deeply indebted to Professor respectively, and one medial branch, the medial P. Nieuwenhuijse, head of that department, and to basal vein (V7, Fig. VIII). Dr. F. Frodl, now of the Department of Radiology, Utrecht, for so generously having granted me access Very occasionally a lung is drained by one pul- copyright. monary vein to these casts. only. Mr. P. Marchand, of the Thoracic Surgical Unit, Johannesburg, made 10 similar casts, and to him I DISCUSSION wish to extend my sincerest thanks for having permit- Several plates of the pulmonary vessels are ted me to include them in this series. presented showing their relations to each other Contributions by Mr. L. Fatti and Mr. G. R. and to the bronchi at the different primary, secon- Crawshaw made possible the publication of drawings http://thorax.bmj.com/ dary, and tertiary hila. in colour. Although, functionally, a lung is composed of " bronchopulmonary " segments, the term REFERENCE " bronchovascular " is sometimes employed, as the Boyden, E. A. (1945). Surgery, 13, 706. on September 28, 2021 by guest. Protected