Radiographic anatomy of the equine lung : a thesis presented in partial fulfilment of the requirements for the degree of Master of Veterinary Science, Massey University

Copyright is owned by the Author of the thesis. Permission is given for

a copy to be downloaded by an individual for the purpose of research and

private study only. The thesis may not be reproduced elsewhere without

the permission of the Author.

RADIOGRAPH I C ANATOMY OF THE EQU I NE LUNG

A thes i s presented i n part i a l

fu l fi l ment o f the req u i rements for the deg ree of Ma ster of Veteri nary Sci ence .

GARRY NE I L SANDERSON

Massey U n i vers i ty February 1982

Abs tract of a thesis presented i n parti al fulfi l ment gf the req u i rements for the degree of

Master of Veteri nary Sc i ence.

RAD I OGRAPH IC ANATOMY OF THE EQUINE LUNG

GARRY N E I L SANDERSON

Thi s resea rch proj ect wa s i ns t i gated i n an a ttempt to p rov i de i nforma tion on the rad i ograp h i c anatomy of equ i ne thorax wh i ch would e nable s peci fi c i n terpretati ve cri teri a to be d eveloped i n the di agnos i s of equ i n e pulmonary condi ti ons . In order to accurately characteri se the s t ructures i n the thorax a number of ex i s ti ng i nvesti gati ve tec hni ques had to be mod i fi ed for use i n eq u i ne subj ects .

a .

I n the absence of an ex i s ti ng method at the t i me � a s i mple method of perform i ng bronch ograms on standi ng con s c i ous horses was developed . The techn i que i nvolved i nsufflati on of 1 0 0 - 200gms of fi nely powdered Bari um Sulphate mi xed with 3 -7gms of powdered me thyl cellu l ose from an ether vapouri ser connected to an i ntra

tracheal tube a n d suppli ed w i th compressed a i r from a gas

cyl i nder . Good vi suali s a ti on of bronchi al bran ches d own to the seventh a nd e i g h th genera ti ons were obta i ned i n all but the mos t dorsal bronchi al branches . Eli mi nati on of resi dual contrast a gent was rapi d and i nflammatory res ponse determ i ned by s eri al h i s tologi cal stud i es was mi n i mal .

Attemots a t pulmonary a rteri a l angi ography i n the stand i ng horse were abandoned owi ng to adverse pati ent reacti on i n favour of a simi1ar technique i n anaestheti sed animal s, however a s a resu l t

b .

of difficu l ti es encountered wi th thi s techn i que only a sma l l seri es of angiograms was performed wi th m i xed resu lts .

Fume fi xati on of th e eq u i n e l ung was performed u t i l i s i ng the hot formal i n v a pour tec hn i que of Wri ght et .

�

. ,

(

l974

)

resulti ng i n the successfu l producti on of severa l sets of 11phantom11 l u n g s on wh i ch exten s i ve r adi o l og i c a l and gross anatom i c a l stud i es were performed i n an attempt to relat: the 1 1 i n v i tro 11 a ppearances wi th those

of p l a i n radi ogra phs of the thorax of s tandi ng horses .

Carefu l exami nati on of the resultant rad i ographs and corre l a ti on of d i fferi ng a ppearances prov i ded by the contrast techn i ques demonstra ted a number of i mportant di agnosti c poi nts . On the p l a i n rad i ograph a greater number of generati ons of pu l monary a rteri es , vei ns a nd bronchi can be accurately i denti fied i n the horse compared to othe r s peci es . In addi t i on , despi te a

s i m i l ar s u bgross and s uperfi ci a l radi ographi c anatomy to man , the horse demonstrates an a rteri a l and venous branchi ng pattern exact l y the reverse i n a ppearance . Thus monopodal bra n ch i ng i s a fea ture of the pul monary arteri a l system whereas d i c hotomous smoo th branch i ng is the norm for equ i ne p u l monary vei ns.

Marked between anima l vari ati on i n the pattern o f bron ch i al branch i ng was a l so noted howe�e r i t was not determi ned i f thi s was a t rue

vari at i on in anatomi c a l branchi ng or the res u l t of wi d e l y vary i ng degrees of bronch·oconstri cti on . The ¹ atter effect was very ma^rked

in some bronchograms when atropi ne s u l phate wa s not used pri o r

to ba ri um s u l phate i n suffl a t i on duri ng bronchog(a phy . Perhaps the mos t i mportant res u l t of the corre l ati ve study was the ability to a ccurate l y i denti fy bronchi a l and vascu l ar branches

over the greater poi nt of the l ung f i e l ds as a resu l t of pri o r knowl edge of the i r branch i ng patterns obtai ned from the contras t studi es .

No a ttempt was made i n th i s s tudy to re l ate the rad i oanatom i c a l fi nd i ngs t o known c l i n i ca l l y apparent pul mona ry condi ti ons . Such research was he l d to be appropri ate for a fo l l ow up study .

c .

ACKNOWLEDGEMENTS

I would l i ke to record my grati tude to the Equ i n e Research Fou nda t i on

,

a nd to the trustees of the Norman Cunni ngham Fell ows h i p for fi nancial a s s i stance throughout the period of t h i s s tudy .

I am grateful to Dr . Mi ke o•ca l l aghan , my superv i so r , for h i s gui dance a nd encouragement duri ng thi s study , a nd to my

eo-supervi sors Drs . B . E . Goul den and H .G . Pearce for thei r s u p port . Wi thout the techn i cal experti s e and cons i derabl e pati ence of Ki rsty Caro , the veterinary c l i n i c radiographer , th i s thes i s coul d not have been p roduced .

I thank Rex Fa ul d i ng for hi s techn i ca l assi stance a nd Tom Law for hi s fi ne photography , a l so the staff of the Massey Vete r i nary

Cl i n i c for the i r assi s tance .

To my wi fe, Rebecca , thank you for you r understand i ng and con s ta n t encoura gement for the per i od of study .

TABL E OF CONTENTS

Page No .

List ^of fi g u res

List of tabl es Int;oducti on

Chapter I : L i teratu re Revi ew 3

Thora c i c Radi ol ogy

(

A

)

Genera l 3

Ana tomy of the Lung

(

B

)

Pl a i n Radi ol ogy 3

(

i

)

sma l l ani ma l s pec i es 3

(

i i

)

l arge ani mal s pec i es ⁵

(

C

)

B ronchography 6

(

i

)

Human bronchogra phy ⁷

(

i i

)

Can i ne b ronc hog ra phy 9

(

i i i

)

L a rge a n i ma l spec i es 13

(

A

)

G ross Ana tomy 14

(

B

)

Su bgross Anatomy 14 I nterpreta t i o n of Pu l mon a ry Rad i ographs Based on

Pattern Recogn i ti on 20

(

A

)

V ascu l ar pattern 20

(

B

)

B ronch i a l pattern 23

(

C

)

Intersti ti a l pattern 24

(D)

A l veo l ar pa ttern 27

Lung Fi xa t i on 29

Chapter I I Mater i a l s and Methods 32

Pl a i n Rad i ography of the Equi ne Thorax 32 Corre l a t i v e Study of t he Equi ne Thorax

i nvol v i ng Speci a l Procedures 33

(

A

)

P u l monary Ang i ogra phy 33

(

B

)

B ronchogra phy 35

Page No . t�orphol og i ca l Study of I sol ated Equ i ne Lungs 42

(

A

)

Emba l m i ng Equ i ne Lungs 42

(

B

)

I nvesti gat i ons on Emba l med·Lungs 43

(

i

)

P l a i n Rad i ography 43

(

i i

)

Use of Contras t Agen ts i n

Embal med Lungs 44

(

i i i

)

Hi s to l ogi ca l Ana lyses 44

Chapter I I I Bronchography i n the Horse Res u l ts

(

i

)

Bronchog rams

45 45 54 55 56 61 61

(

i i

)

E l i mi nati on of Bari um

(

i i i

)

Hi stol og i ca l Respons e D i s cu s s i on

Chapter IV Pul monary Vascul ature i n the Horse Resu l ts

(

A

)

Pu l monary Arteri ogra phy

( B) Rad iography of Di s sected Equ i ne Lungs 72

D i scus s i on

(

i

)

Wi thout contrast agents

(

i i

)

Wi th contrast agents

72 73 73 Chapter V Rad i ogra phi cal Anatomy of the Equ i n e Thorax 80

Conc l u s i on References

Resu l ts

(

i

)

Bony Stru ctures 80

(

i i

)

Heart and Great Vessel s

(

a

)

Aorta 80

(

ii i

)

Ai rways D i scus s i on

(

b

)

Pu l monary a rteri e s 8 1

(

c

)

P u l monary vei ns 83

(

d

)

Caudal vena cava 83

(

e

)

Peri phera l vascul a tu r e 83 84 90 93 97

L I ST OF FIGURES

(l) Diagrammati c representa t i on of bronchograms, both norma l and abnorma l (Adapted from Doug l as , 1 970 ) (2) Cha racteri s ti cs of pu l monary ves se l s as seen on

human chest rad i ographs

(3)

Di ag ram of the sys tem for del i veri n g powdered bari um

Page No.

12 22

s u l phate to the l un g s 40

( 4 ) Di agram of a system for emba l mi n g equi ne l u ngs 42 ( 5 ) Pl a i n , l eft l a tera l rad i ograph of d i aphragmati c

a rea of a normal horse 46

( 6 ) Bronchogram of an adul t horse 47

( 7 ) Di ffi cu l ti e s encoun tered wi th eq ui ne bronchog rams 48 ( 8 ) Demonstrat i o n of the marked var i at i on of bronch i a l

pa tterns from d i fferent hors es 49

( 9 ) Bronchogram of a 24 yea r ol d mare wi th a h i s tory

of chron i c coug h 5 0

( 1 0 ) Radi ographs ta ken to i l l ustrate t h e rapi d ( a , b , c )

e l i m i na t i on o f bari um sul phate from the a i rways 5 1 ^& 52 ( 1 1 ) Bronchogram taken 10 mi nutes post-i nsuffl ati on to

i l l u stra te bo l us of contra st materi a l wi th i n the

oesophag us 53

( 1 2 ) Exposure to check pos i t i on of i ntra -arteri a l cathete r

p r i o r to angi ography 64

( 13 ) Pu l monary a rter i og ram of s i x -mon th pony foa l 65 ( 14 ) P l a i n rad i ograph of thorax of year l i ng Thoroughbred col t 6 6 { 15 ) Pu l monary a rteri og raph o f yearl i ng Thoroug hbred col t 6 7 ( 16 ) Pu l monary v enogram i n yearl i ng Thoroughbred col t 68 ( 1 7 ) Control exposure of yearl i n g Thoro ughbred col t 69 ( 18 ) Pu l mona ry a rteri ogram of yearli n g Thoroughbred col t 70 ( 19) Pul mona ry a rteri ogram of yearl i ng Thoroughbred col t 7 1 (20) Dorsoventral rad i og raph of i sol a ted r i g h t l ung o f 18-mo n th

Thoroughbred g e l di n g 7 4

( 2 1 ) Dorsoventra l rad i ograph o f i sol ated ri ght l un g of 2 year

o l d Thoroughb�ed fi l l y 75

L I ST OF FIGURES

(22) Photographs of s ecti ons of fi xed l u ng from 2 year ol d T�oroughbred fi l ly

(23)

Dorsoventral radi ograph of the i sol ated l eft l ung of a horse fol l owi ng fume fixati on a nd i nfu s i on of aqueous bari um sul phate i nto the pu l monary arteri a l sys tem

( 24) An enl arged v i ew of a sect i on of Fi g .23 s howi n g a

Page No.

76

77

compa ri son of a rteri a l and venous branchi n g patterns 78 (25 ) La tera l rad i ograph of horse•s l u ng fi e l d demon s trat i n g

ma i n anatomi cal features 85

(26 ) Card i a c area of l ung demonstrati n g peri h i l a r deta i l s 86 (27 ) Demonstra t i o n of posi t i on of cari na rel a t i v e to

aorta and pu l monary a rtery by b ronchography 87 (28 ) Rad i o graph h i g h l i g h t i n g the po s i t i on and course

of the ma i n pul monary arteri es 88

(29 ) Demon s trati o n of pos i ti on of pul monary vei n s on

the thora c i c rad i ograph 89

L I ST OF TABLES

(1) Subgross Morph o l ogy of Hors� Lung compared wi th that of severi other s pec1es

Adapted from Tyl er et . a l . , ( 1 97 1 )

(2) Summary o f Bronchogra phi c Techn i q u e and Res u l ts

Page N o .

17

36-3 8