SURGICAL ANATOMY THEANALCANAL special

SURGICAL ANATOMY OF THE ANAL CANALwith special reference to the

SURGICAL IMPORTANCE OF THEINTERNAL SPHINCTER AND CONJOINT

LONGITUDINAL MUSCLEby

C. Naunton Morgan, M.S., F.R.C.S.and

Henry R. Thompson, F.R.C.S.Consultant Surgeons, St. Mark's Hospital

"If terms be incorrect, then statements do not accord with facts; and whenstatements and facts do not accord, then business is not properly executed."

Confucius

THE DESCRIPTION BY Milligan and Morgan (1934) of the surgical anatomyof the anal canal with reference to fistula-in-ano and that of Milliganet al. (1937), on the treatment of haemorrhoids, is essentially correct forthe normal anal canal when examination is carried out without anaesthesia.The fact, however, that the relationship of the anal musculature alteredunder anaesthesia was not realised and resulted in the misnaming of theinternal sphincter. At operations for haemorrhoids and fissure-in-ano,this muscle in the original descriptions was confused with the subcutaneousexternal sphincter.

Division of the internal sphincter muscle (sphincterotomy), describedby Eisenhammer (1951), for " Chronic Internal Anal (Sphincteric)Contracture" re-focused our attention, at St. Mark's Hospital, on theexact position of the internal sphincter. The work of Fine and WickhamLawes (1940), Wilde (1949) and, more recently, Parks (1954), togetherwith the co-operative investigations over several years by the Surgical Staffat St. Mark's Hospital (Goligher et al., 1955), now enables a more accuratedescription of the anatomy of the anal canal to be presented.The object of this paper is:(1) To distinguish between the anatomical and surgical anal canal and

to give a more accurate description of its anatomy and terminology.(2) To indicate how the terminal attachments of the conjoint longi-

tudinal muscle may determine the path of perianorectal infection.(3) To describe variations and conditions in which the relationships of

the external and internal sphincter are altered.(4) To correlate the internal sphincter and the pecten band.(5) To correct a point in previous anatomical descriptions from St.

Mark's Hospital.(6) To describe the operation of sphincterotomy.(7) To draw attention to a common error in conception of the anorectal

musculature.

88

SURGICAL ANATOMY OF THE ANAL CANAL

THE ANATOMICAL AND SURGICAL ANAL CANALS

The anatomical anal canal extends from the level of the valves ofMorgagni (dentate line) to the anal margin.For surgical purposes, the anal canal may be regarded as that portion

of the terminal intestine which extends from the level where the rectumpasses through the pelvic visceral aperture- the anorectal ring-to thethe anal margin. This concept of the anal canal is more apposite forsurgical] purposes and as the anorectal ring is above the valves ofMorgagni, the surgical anal canal is longer than its anatomical counter-part (Fig. 1).

Anorectal rin(pelvic viuceriaperture)

Surgical anal canal

Anal marsin

Fig. 1. The surgical and anatomical anal canals.

THE LININGS OF THE SURGICAL ANAL CANAL (Fig. 2)The pink columnar mucous membrane of the rectum extends down-

wards from the anorectal ring into the anal canal and overlies the upperhalf or two-thirds of the internal sphincter. It is loosely attached to theunderlying structures and covers the internal haemorrhoidal plexus. Asit approaches the level of the columns of Morgagni, the columnar mucousmembrane becomes cuboidal, is darker in colour, and, just above the

89

C. NAUNTON MORGAN AND HENRY R. THOMPSON

./1..

Anorectal 4. ,ring (pelvic

visceral o i u Rectalaperture) 9X, mucosa

... . . I *.~~~v*~ (pink)

. - .AnaConjoint mucosa

longitudinal (re.

Anal

sphncltaler fMran,bcmslmclue hr it coer coloured)

On proctoscopy, this region of the a~ ~~~~~nal canalpoet iteit h

External v t ofanssphincter c

Fig.2.unthe iingsuoferthe analhcanal,anbth anlmscuatuiregua.wv

analhvalves of Morgagni, becomesr plum colouredawhereitcorsthe mecaol inmnatson the in lhaemorroid an eis no k nathe AaMe o.

Onprctescopy etheirio nof the anal canalp a into Theinstrument dceofot interlhaemorot idal p sin

Thersubmucou spaiflcle. ,seto uosgad,adi assipr

cuaeptibl inoteloe hce n imne orgtd true skinoAthert anal vvs, thellicnin cangesfmo ans

epithbelwiuand athte lfeine dsthe analcanal tontsq moustfaletthelitahs latterchantgre althamouhoab t es not Take paone Anas reularin aproutn thea thcirmerenceof the bwl,butaasaoes irreg wyatv

Tahe samonal epithe lining chasgeen cetranal canal skin .Tansitionsanalpcahalm nd,of theparcentn colthe deliaes,tesmr ot, tus aen htwin.

Therelattre nohairefltolliles swatruor muous glnds,tanditac passes imeglr-cepctibly ineto theloose,digthickeroandopigentedincorrugthed truetskin of

JpthlustIthabelowferdoa the dentateline.teaaaalsisms fecirml attahedjntionthdeeper structures-Hilton'swheitheline. Thet zonte betweenthdeTate lineandu eptheliadhernghabentclehanal canalskin.wsdsrbdbSTroud

Owtilyingto the loose,attachmentaof thgenmucos coveringae thue sinterna

hdnatemorrhoindalpeubvthe tetheredtanal canal skin anesrbd theStloose

attachment of the skin over the external haemorrhoidal plexus below, twopotential spaces are formed. They are the submucous space which is

90


situated above the level of the anal valves (dentate line) and the sub-cutaneous perianal space placed distal to the adherent anal canal skin.Both these spaces are capable of distension, by inflammatory exudate,venous engorgement, blood clot or injected fluid (Fig. 3).The fixity of the thin anal canal skin (pecten) to the underlying

structures between these potential spaces prevents its detachment fromthe subjacent tissues at this site (Parks).The true skin of the anus and anal canal skin cover the external

haemorrhoidal plexus. Short connecting vessels pass upwards under thesmooth anal canal skin to the internal haemorrhoidal plexus.

. I .

Submucous space

-Adherent anal canal skin

Subcutaneous perianal space

Fig. 3. The submucous and the subcutaneous perianal spaces.

918


The lining of the anal canal above the anal valves is insensitive exceptto stretching, such as by rapid injection of an internal haemorrhoid,whereas the anal canal skin and the true skin of anus are extremelysensitive to painful stimuli.To summarise-the surgical anal canal is lined from above downwards

by pink rectal mucosa (columnar epithelium) covering the haemorrhoidalpedicle at the anorectal ring; by dark red anal mucosa (cuboidal andtransitional epithelium) covering the main haemorrhoidal mass; bysmooth, parchment coloured anal canal skin (thin squamous epithelium)covering the pecten zone and, finally, by the true skin of the anus(squamous epithelium with hair follicles and sweat glands) covering theexternal haemorrhoid.

THE ANAL MUSCULATUREThe internal sphincter (Fig. 2)The internal sphincter is the thickened terminal portion of the circular

muscle coat of the rectum. It arises where the rectum passes through thepelvic diaphragm and its termination can be felt just within the analorifice. Its position and relation to other structures of the anal canal andits variations will be described subsequently.

The conjoint longitudinal muscle (Fig. 2)The conjoint longitudinal muscle of the anal canal is formed by the

continuation downwards of the longitudinal muscle coat of the rectumtogether with fibres from the puborectalis muscles. As this thickenedconjoint muscle passes downwards between the internal sphincter and theexternal sphincter, its fibres become more and more fibro-elastic.

Whilst lying between these sphincter muscles, some fibres of the longi-tudinal muscle pass inwards through the internal sphincter, between itsmuscular fasciculi, to enter the submucous space. This is most clearlyshown in foetal sections (Figs. 4a and b). Here the fibres appear to con-dense mainly in the region of the inner aspect of the enlarged distal portionof the internal sphincter. In this situation, the muscularis mucosae of thebowel is much thicker and the longitudinal " muscle " fibres apparentlypass into it. Fine and Wickham Lawes (1940), have called this sub-mucous fibro-muscular layer the musculus submucosae ani. In this region(pecten) the anal canal skin is attached to the subjacent fibro-muscularlayer and indirectly, therefore, to the lower portion of the internal sphincter(Fig. 5).

This attachment of the longitudinal muscle to the lining of the analcanal separates the submucous from the subcutaneous perianal space.It should be noted that the perianal space extends upwards within theanal canal for a short distance and that the thickened lower end of theinternal sphincter lies within this subcutaneous space.

92


_@.@;wg~~~~~~~~~~N AM r §it #t

(With acknowledgment to Prof. H. Butler.)

Fig. 4a. Coronal section of ano-rectal region of foetus.

Some fibres of the fibro-elastic termination of the longitudinal muscleloop around the lower border of the internal sphincter to join the inner-most fibres of the conjoint longitudinal muscle (Wilde).The main insertion of the fibro-elastic fibres of the conjoint longitudinal

muscle is into the true anal skin overlying the subcutaneous externalsphincter. This insertion is obtained by fanning out of the longitudinalfibres which then pass through the circular fibres of the subcutaneous

938-2

id


external sphincter. Some of these fibres lie immediately under the skinof the anal canal and skin of the anus and constitute the corrugator cutis-ani muscle (Ellis (1878) and Milligan (1942)). Other fibres of the longi-tudinal muscle pass outwards between the subcutaneous portion and

Longitudinal muscle

_. eS$ sii ;0 Internal sphiencter

E > 2 t Subcutaneousexternal sphincter

Fig. 4b. Magnification of area marked on 4a. This shows fibres of thelongitudinal muscle not only passing through the subcutaneous external sphincter

but also through the internal sphincter.

deeper portions of the external sphincter, across the ischio-rectal fossa,dividing it into perianal and ischio-rectal spaces. To a lesser degree, itsfibres pass between the deeper portions of the external sphincter muscle(Wilde, 1949). Anteriorly, the longitudinal muscle fibres become attachedfirmly to the triangular ligament, to the urethra and to the apex of theprostate and represent the recto-urethralis muscle. This attachmentholds the rectum to these structures and may be identified during perinealdissection of the rectum.

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4 ~ - iRed rectal mucosa

.9.

i.'~~~~~~~~~~~ ~ ~~~~~~~~~~~~~~~~~ .... .....

Anal canal skin

b~~~~~~~~~~~~~~Si of anus |

Fig. 5. Longitudinal section of anal canal. The fibres of the longitudinal musclepassing through internal sphincter will be seen to condense under the anal canal

skin at X.

(With acknowledgment to F. R. Wilde, F.R.C.S.)

95


Fig. 6a. The visible inter-haemorrhoidal depression.

By virtue of its wide attachments, the conjoint longitudinal muscleforms an important integral part of the anorectal musculature. Since thebulk of its fibres pass through the sphincter muscles to gain their attach-ments, it binds and braces them together.As already stated, the anal canal skin is anchored to the underlying

tissues, whereas the mucosa covering the internal haemorrhoid (sub-mucous space) above and the skin over the external haemorrhoid (perianalspace) below are loose and project. Thus the fixed portion of the analcanal lining is seen as a depression on a prolapsing haemorrhoid. Thisdepression in fact separates the internal haemorrhoidal plexus (internalhaemorrhoid) from the external haemorrhoidal plexus (external haemorr-hoid) and is an inter-haemorrhoidal depression. When a second degree

96


haemorrhoid prolapses and becomes inflamed or thrombosed, this inter-haemorrhoidal depression is most plainly seen (Perrin).

Just within the anal orifice, between the inner aspect of the subcutaneousexternal sphincter muscle and the lower border of the internal sphinctermuscle (the thickened innermost portion of the circular muscle coat of therectum), a distinct depression is palpable. This depression has been calledby Milligan and Morgan the anal intermuscular depression and inprevious descriptions was considered to coincide with the attachment ofthe intermuscular septum (one of four fibro-muscular expansions of thelongitudinal muscle) to the lining of the anal canal. It is, however, notpossible to demonstrate such a direct attachment of the longitudinalmuscle to the anal lining.

I

Fig. 6b. The palpable intermuscular depression.

97

11

N

11-. maw,,KM \

Wh.'l`444


The visible interhaemorrhoidal depression is distinct from the palpableanal intermuscular depression and bears no fixed relation to this landmark(Figs. 6a and b).

It has always been difficult to understand why infection so readilypasses through such a relatively stout muscle as the internal sphincter,or through or between the external sphincters. The fact that fibres of the

Fig. 7a. Diagram of intermuscular abs-cess indicating possible paths of spread.

Fig. 7b. Fistula resulting from inter-muscular abscess.

longitudinal muscle pass both inwards through the internal sphincterand also outwards between portions of the external sphincter muscles mostprobably accounts for the routes by which infection extends directly fromthe anal canal into the perianorectal tissues to form an abscess or fistula-in-ano. Conversely, it would explain how an abscess, which takes theline of least resistance along a fascial plane or other anatomical pathway,may track from the ischio-rectal space along the fibres of the longitudinalmuscle in between the fasciculi of both the external and internal sphinctermuscles to burst into the anal canal.

It is not uncommon to find an abscess or a fistula extending upwardsbetween the internal and external sphincter muscles. This extension mustoccur along the main portion of the longitudinal muscle. Such an abscess

98


displaces the external sphincter group outwards away from the internalsphincter and may enter the anal canal at any level by extending throughthe internal sphincter along a fasciculus of the longitudinal muscle. Thefistula resulting from such an abscess will require division of a portion ofthe internal sphincter alone to cure it; the external sphincter muscle isleft intact (Figs. 7a and b). The multiple extensions of the longitudinalmuscle through the internal sphincter may also explain the not uncommonoccurrence of more than one internal opening. Failure to appreciate thispossibility and to identify a second internal opening, is one of the reasonsfor persistence of a fistula after surgical treatment.

ANATOMICAL RELATIONSHIPS OF THE INTERNAL AND EXTERNALSPHINCTER ANI MUSCLES

The relative positions of the lower portion of the internal sphincterand the subcutaneous external sphincter may be altered. The changesin position will be discussed under the following sub-headings:

(a) Variants of normal anatomy.(b) The effect upon the sphincter of lateral traction on the perianal skin.(c) Effect of anaesthesia on sphincter tone.(d) Digital eversion of the anal canal (Miles).(e) Positional sphincter changes in certain pathological states.(f) Distortion in anatomical dissections and microscopical prepara-

tions of the anal canal.

(a) Variants of normal anatomyThese are found in both the subcutaneous external and the internal

sphincter. The former usually consists of an annular band of commissuralfibres but these commissural fibres may be replaced by slips of musclefibres passing down on their respective sides to become continuous withthe superficial portion of the external sphincter (Gorsch). The analintermuscular depression in such subjects is felt posteriorly as a deep pitinto which the tip of the finger may be inserted.

In rare instances the anus projects from the perineum in a conicalmanner. This can be shown to be due to an elongated hypertrophiedinternal sphincter. On inserting the finger into the anus, no anal inter-muscular depression is felt since the subcutaneous external sphincterencircles the base of the projection and any palpable depression issituated outside the anal orifice (Fig. 8).Many intermediate stages between this extreme and the normal may be

recognised and it is interesting to speculate whether variations in therelative size and position of the internal and external sphincter musclesis in any way related to function and pathology.

(b) The effect upon the sphincter of lateral traction on the perianal skinContinuous lateral traction on the perianal skin during examination

may cause the external sphincter to dilate slowly. This dilatation alsooccurs in the lithotomy position when the perianal skin is again drawn

99


taut laterally. The phenomenon is reproduced when squatting to defaecateand is probably an initiating factor in the intricate mechanism of defaeca-tion.

After the external sphincter has dilated and the faecal bolus is extruding,the conjoint longitudinal muscle, which passes fan-like through thesubcutaneous external sphincter, contracts and draws up this relaxingmuscle over the faecal bolus. This everts the anal canal and changestemporarily the relationship of the subcutaneous external sphincter andthe internal sphincter.

(b)

Right buttock eSubcatsneousexternal sphincter

Internal sphlincter

/O~

ANTR

Internal sphincter

Left buttock

(a)

(c)

Fig. 8. Anatomical variant of the internal sphincter muscle.

(a) Drawing from photograph taken from behind with patient in left lateralposition showing anus projecting from the perineum as a cone.

(b) Diagrammatic section of normal anal canal to compare with(c) Diagrammatic section of conical anus.

100

p0

TR


(c) Effects of anaesthesia on sphincter toneThe anal canal is opened and closed by the synergistic action of both

somatic and visceral muscle, although the exact mechanism as yet isincompletely understood. Inberg of Helsinki (1952) has shown thatfollowing the intravenous injection of tetraethylammonium chloride, inorder to block the nerve supply to smooth muscle, the tone of the internalsphincter is diminished. The combined sphincter tone, however, isincreased for a period due to compensatory contraction of the externalsphincter.Under anaesthesia the somatic external sphincter muscle relaxes,

whereas the visceral element, the internal sphincter, retains its tone(Fig. 9a and b).The response of the external sphincter ani muscle to anaesthesia was

a subject of comment by Miles. He wrote:

" Stretching of the external sphincter is supposed to be necessary because it issaid not to relax even when the patient is deeply anaesthetised. It is, however,unreasonable to suppose that the external sphincter differs from the remaining519 voluntary muscles of the human body in its reaction to anaesthesia. As amatter of fact, it is just as susceptible to anaesthesia as any of the others, but it isincapable of becoming relaxed on account of the constricting effect of the pectenband. When the pecten band has been divided it is found that the externalsphincter relaxes under the influence of anaesthesia just like any other voluntarymuscle. It is not possible to stretch the pecten band. Consequently, if forcibledilatation of the anus is reverted to, the band is torn."

The pecten band, as will be shown, is in fact the internal sphincter(visceral muscle) which does not relax under anaesthesia; and if it hasbecome fibrosed, as in haemorrhoids or fissure-in-ano, it may indeedrequire division for full relaxation of the anus.The subcutaneous external sphincter relaxes under anaesthesia and is

displaced outwards and upwards, whilst the rounded lower border of theinternal sphincter is now placed at a lower level near or at the anal orifice(Fig. 9b). Estimation of the length of the normal anal canal from theanorectal ring to the anal verge, before and during anaesthesia, shows thaton relaxation of the anorectal musculature the anal canal may be shortenedby as much as one centimetre.At operation, traction upon the pedicles of prolapsing haemorrhoids

will evert the anus still further and the internal sphincter is pulled downwell below the subcutaneous external sphincter (Fig. 10 a, b and c).Because this change in muscle relationship was not appreciated, theinternal sphincter has been erroneously labelled the subcutaneous externalsphincter in descriptions of the St. Mark's operation for haemorrhoidsprior to 1955. The correction of this error in no way modifies the techniqueof the operation or the principles on which it is based. The description ofthe dissection of haemorrhoids at this operation should read: The bladesof the scissors are placed, one at the muco-cutaneous junction and the

101


other at the outer border of the external haemorrhoidal plexus. AV-shaped cut is made: a limb on either side of the skin holding forceps.The cut is made through the skin and the underlying radial fibres of thecorrugator cutisani muscle (conjoint longitudinal fibres). The perianalspace is now entered and the white circular fibres of the internal sphincter

Internal sphincter

Internal sphincter

Subcutaneousexternal sphincter I

Subcutaneous(a) external sphincter (b)

Fig. 9. Showing the effect of anaesthesia on the relationship of the subcutaneousexternal and internal sphincter muscles.

(a) Closed anus. (b) Anus relaxed under anaesthesia.

muscle are exposed. The external haemorrhoid is dissected inwards withscissors and the internal sphincter muscle bared to its inner border. Herethe fibres of the conjoint longitudinal muscle will be seen passing throughthe fasciculi of the internal sphincter into the dissected haemorrhoid. Itis possible to slide or imbricate these fasciculi upon one another bytraction on the dissected pile.

Ligation of the mucosa of the pile pedicle and its vessels will incorporatethe longitudinal fibres, so anchoring the pile pedicle to the internal

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sphincter. This will prevent upward retraction of mucosa to its originalsite, thus obviating a large, raw area (Fig. 11 a, b and c).

It is emphasised, therefore, that the prominent ring of white circularmuscle exposed at the St. Mark's operation of haemorrhoidectomy is notthe subcutaneous external sphincter but the internal sphincter.(d) Digital eversion of the anal canal

Digital eversion of the anal canal was practised by Miles in his operationof pectenotomy.The patient was placed in the right lateral and semi-prone positions,

the index finger of the left hand was introduced as far as the terminalinterphalangeal joint and then firmly flexed, at the same time the thumb

(a) (b) (c)Fig. 10. Showing effect of traction on the relationship of the subcutaneous

external and internal sphincter muscles.(a) Anus relaxed under anaesthesia with skin forceps applied.(b) Forceps applied to secure haemorrhoidal pedicle.(c) Traction on haemorrhoidal pedicle everting the anus and pulling the internal

sphincter below the subcutaneous external sphincter.

of the left hand pressed the skin of the anus outwards. He claimed that thisdisplaced the inner border of the external sphincter outwards, and bydividing the mucosa of the lower part of the anal canal, the pecten bandwas exposed (Fig. 12). Division of this band, pectenotomy, was the Milesoperation for fissure. (Fig. 13).

Miles (1919) originally described the pecten band as" a band varying in thickness and in density and giving the impression to the

examining finger as if a rubber umbrella ring had been inserted beneath the skinat the anal margin."He has subsequently described it (Miles, 1939) as a deposit of fibrous

tissue, circularly disposed in the submucosa of the part of the anal canalbetween Hilton's white line and the edges of the Morgagnian valves(pecten zone).The existence of the pecten band as a separate entity, distinct from the

anatomical structures of the anus, has never been accepted at St. Mark'sHospital. Fine and Wickham Lawes (1940) expressed surprise that

103


universal recognition had not been accorded by proctologists to itsexistence. Miles asserted that the pecten band did not occur in thehealthy anal canal but Abel (1932) and Spieseman (1938) agreed that apecten band might exist without any associated pathology in theanorectum.

Fine and Wickham Lawes (1940), were of the opinion that Miles andAbel (1932), influenced by the physical characteristics of the pecten bandand the contrast of its white fibres to the red fibres of the external sphincter,concluded it was of fibrous nature. The same authors demonstrated infour biopsy specimens of the pecten band, that all contained involuntaryunstriped muscle fibre, and remarked that its pallor was quite compatiblewith unstriated muscle.Thus it may be inferred from the above paragraphs that the " pecten

band " is a white band, situated under the skin of the anal canal, varyingin thickness, seen in the healthy and diseased anorectum, consisting of

*~~~~~~~~~~~~~~~~~~~~~~~~.... .:.. .... i;..,. .. ..-..

WDrawn down fasciculus of

internal sphincter still coveredby longitudinal fibres

(a)(b)(c)

(a) (b) (c)Fig. 11. Dissection of the left lateral haemorrhoid at haemorrhoidectomy.Skin divided, exposing corrugator cutisani muscle.

iIncision deepened, exposing lower border of internal sphincter muscle.IWith wider skin cut, both internal and external sphincter divided.

(See Figs. 12 and 13.)

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.. ? I

Fig. 12. The linear incision through the anal skin gapes widely, exposing A, thepecten band, and B, the innermost fibres of the external sphincter muscle.

.:~~ ~~~~ ....:emYz .... .. ........

PIC TEN BAND

Fig. 13. The patient lyIng in theright.lateral. s.emi prone positionthelower.parti . e § 4 ;} | I ..~~~~~~~~~~~~~~~~~~~~~~~~~~~~~........ .

oftheana_l canalis everted to.render.prominent.the pecten..band whichisdivided

$::sez u__ ~~~~~~. 8k.,::.... ;:

.i:: ................... ':':: . ..~~~~~~~~~~~~~~.......

Fig 13 Th ain lyn in th rih latrl sem-rn psto,he lower part

in the right posterior quadrant of the anal orifice.Figs. 12 and 13. In reality a linear incision over the everted anal canal, afterdividing the longitudinal fibres of the corrugator cutisani muscle, exposes theinternal sphincter and the subcutaneous external sphincter. Miles in fact called

the fibrosed internal sphincter muscle the pecten band (see Fig. 1 1)(These two figures are taken from Miles Rectal Surgey (1939) by permission of Mrs. Ernest Miles

and Cassell & Co London)

105


circularly disposed unstriped muscle fibres, division of which cures afissure-in-ano. This corresponds closely to the description of the internalsphincter muscle as recognised at St. Mark's Hospital, except to add thatsuperiorly it is continuous with the circular muscle coat of the boweland that externally lies the main portion of the conjoint longitudinalmuscle.A fissure-in-ano is a painful tear of the skin of the anal canal and varies

in length and depth. When uncomplicated by inflammatory changes it

'.k..,. j' X , .. .4 ;'~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~.... .

........

Fig. 14a. Sentinel tag of posterior Fig. 14b. Anus everteJ to demonstrate acutefissure in ano. fissure with longitudinal fibres in floor of

fissure.

cannot be seen unless the anus is everted. Pain and muscular spasm aresuch that this cannot be readily achieved without a surface or otheranaesthetic. A fissure does not extend upwards above the muco-cutaneousjunction where, at its apex, an anal papilla is frequently present. It doesextend downwards to the true skin of the anus, where inflammatorychanges lead to the formation of the tell-tale skin tag or sentinel pile andMilligan (1942) has suggested that fissure-at-anus is as correct a term asfissure-in-ano.

In an acute fissure, when only the anal canal skin is broken, radiatinglongitudinal fibres will be seen in the floor of the fissure; these unstripedmuscle fibres are derived from the fibres of the conjoint longitudinalmuscle which have traversed the lower end of the internal sphincter.Some of the longitudinal fibres passing through the innermost portionof the subcutaneous external sphincter may also be exposed (Fig. 14a andb). When a fissure has become chronic the longitudinal fibres disappearand now fine white circular fibres appear across the floor of the fissure(Fig. 15).An investigation into the tissue seen in the floor of a fissure-in-ano was

commenced five years ago at St. Mark's Hospital. Now, following apersonal. experience (H.R.T.) of 300 operations for anal fissure, whichhas been confirmed by our surgical colleagues at St. Mark's Hospital,

106


it has been shown beyond doubt that division of these white circular fibresrelieves the pain and results in the healing of a fissure-in-ano. Fromanatomical dissections and biopsies made at the time, it can be categoricallystated that they are unstriped muscle fibres of the internal sphincter animuscle.

In the course of this investigation, Miles' method of everting the analcanal has been practised many times. It has always resulted in displacingthe subcutaneous external sphincter outwards and in bringing down thelower border of the internal sphincter. Before either muscle can be dis-played, radial longitudinal fibres must be divided.The differences in texture and colour between the internal sphincter

and the subcutaneous external sphincter are so characteristic that, onceseen, it is impossible to confuse them. The internal sphincter is composedof fine, closely packed, white fibres, whilst the subcutaneous externalsphincter consists of coarser, loosely packed, reddish brown fibres. Arecent clinical assistant at St. Mark's Hospital, H. J. Hambury, mostaptly described the difference in appearance as that between the meatof the breast and leg of a chicken.

Patients sometimes tolerate a fissure for months and even years. Insuch cases fibrotic changes will most certainly occur in the internal

Fig.15. Chronicfissre Longitudinalmusclefibreshaveulcerated..through... .

2z.... ... .. .i

2 '2j,-

......... , - 3.wE.j_a"J I s X | ~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~..... ......Fig.15. Chronic fissure. Longitudinl mucl fire have..................................ulertd houh

exposing the white circular fibres of the internal sphincter muscle.

sphincter, forming as it does the floor and base of a chronic ulcer. Thisresults in a rigid contracture at the anus into which it is difficult andpainful to pass an index finger. Indeed, in cutting through the toughfibres of the internal sphincter in a long-standing fissure, a grating

107

9


"' Fig. 16a. Posterior fissure-in-ano withpolyp and skin tag.

Fig. 16b. Internal sphincter musclepartly divided.

Fig.`7 16c. Internal sphincter muscledivided, exposing underlying longi-tudinal muscle sheet. Skin tag andpolyp removed. Commissural fibres ofthe subcutaneous external sphinctermuscle when well developed require tobe divided to prevent a "ridge."

108


sensation can be felt. It is only when they are divided that any elasticityreturns to the anal canal.A rigid, fibrosed internal sphincter may be demonstrated without an

obvious breach of surface, such as a fissure. It occurs particularly inelderly people and has been referred to as senile anal stenosis. It is alsoassociated with the prolonged use of aperients, especially medicinalparaffin, which results in the passage of fluid or unformed stools.

There are two possible explanations for the occurrence of fibrosis inthe internal sphincter without an obvious anal lesion. Firstly, fibrosismay be due to recurrent minor trauma caused by the passage of large,constipated stools, alternating with fluid stools, from the habitual misuseof purgatives. Thus the internal sphincter is either grossly overstretchedor inadequately dilated.

Secondly, as Miles has suggested, fibrosis may result from venouscongestion of the haemorrhoidal plexus.

It is likely that these factors operate together. Not infrequently, haemor-rhoids and a fibrosed, contracted internal sphincter are found together.At haemorrhoidectomy in these cases the fibrosed muscle should bedivided. Fine and Wickham Lawes commented on a variation in theamount of fibrous tissue in their four biopsies of the pecten band.We conclude from these observations that the internal sphincter ani

and the pecten band are one and the same structure. It is impossible todemonstrate both structures in the same patient or the same anatomicaldissection. Reference to the internal sphincter, whether fibrosed or not,as the " pecten band " should therefore cease and, except for historicalinterest, should not find a place in proctological literature. This correctionin nomenclature, however, in no way detracts from the value andimportance of Miles' operation of pectenotomy which is, in fact, aninternal sphincterotomy.(e) Positional sphincter changes in certain pathological states

Internal haemorrhoids prolapse owing to the laxity of the subcutaneousexternal sphincter muscle, overstretching of the conjoint longitudinalmuscle fibres and, finally, weakening of the attachment of the anal canalskin to the subjacent tissue, including the lower end of the internalsphincter. When this latter anchorage is strained, the interhaemorrhoidaldepression may be seen externally. It becomes less obvious, and eventuallymay be obliterated, in large third degree haemorrhoids (Fig. 6a.).

Simultaneously with the overstretching of the subcutaneous externalsphincter, the longitudinal muscle also becomes stretched and no longeradequately supports the anal musculature. It is likely that the bracingeffect of its fibres passing through the subcutaneous external sphinctermuscle is lost and this sphincter no longer remains in close relation tothe anal orifice. The distal end of the internal sphincter will now be at acomparatively lower level and may surround the anal orifice and actuallybe more caudally placed than the subcutaneous external sphincter. Under

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these circumstances the anal canal is shortened and the anal canal skinand the interhaemorrhoidal depression are visible at the anal verge. Bypulling the perianal skin outwards on either side with the fingers, thelower end of an internal haemorrhoid may protrude or, on rare occasions,should the internal sphincter relax, the whole anal canal or even the lowerrectum may be seen.(f ) Distortion in anatomical dissections and microscopical preparations of

the anal canalIn rectums removed from the cadaver for anatomical dissections,

muscle relationships are distorted because their attachments are severedand the internal sphincter can invariably be demonstrated at the analmargin. When making longitudinal sections of the rectum for micro-scopic study, the tissues become stretched, exaggerating and distortingthe relations seen in living anatomy.

DIVISION OF THE INTERNAL SPHINCTER(INTERNAL SPHINCTEROTOMY)

The fibres of the internal sphincter may be ruptured by forcible stretchingunder anaesthesia (Recamier), they may be divided, after everting theanal canal and identifying the internal sphincter by palpation (Miles), oran anatomical dissection and section of the internal sphincter may bemade under direct vision. In comparison with the first two methods,section of the internal sphincter under direct vision is to be commendedfor the precision and accuracy with which it can bE carried out.

In the past, at St. Mark's Hospital, the fashioning of a drainage woundwas included in the operation. The patients were admitted to hospitalfor a minimum period of three weeks. Now we believe that the cure of afissure can be achieved in the majority of cases by dividing the internalsphincter under local anaesthesia as an out-patient operation.There is perhaps a tendency to overlook the necessary details in minor

operations performed in the out-patient department. It must be emphasisedthat the same care required for major surgery must be applied to allminor operations upon the anal canal.Selection of patientsSome patients are temperamentally unsuited for any operation under

local anaesthesia, however well this may be given. Further, the fissuremay be complicated by a chronic abscess, a fistula, a large polyp and skintag; or the patient's home may be remote from the hospital. It is betterto admit these patients to hospital and perform the operation underthiopentone anaesthesia. If the operation is performed as an out-patientprocedure, the patient should always be accompanied by a relative orfriend and careful arrangements made for transport home.An anal fissure associated with large haemorrhoids is quite unsuitable

for out-patient treatment. If the internal sphincter is divided in thepresence of large haemorrhoids, the haemorrhoids will prolapse and

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thrombose and the patient's discomfort will be increased instead of beingrelieved. A patient with haemorrhoids and fissure should be admitted tohospital, a haemorrhoidectomy performed, and the internal sphincterformally divided in the wound of the left lateral haemorrhoid. A smallor moderate sized haemorrhoid in the right anterior position may beinjected with 5 per cent. Phenol in almond oil at the time of a sphinctero-tomy as an out-patient.PreparationThe patient is advised to empty the bowel on the morning of operation.

The perianal skin is shaved and prepared with Cetavlon and spirit.

AnaesthesiaWith the patient in the right lateral position, an intradermal weal is

raised in the mid-line posteriorly, one inch from the anal margin, using2 per cent. Xylocaine with Adrenaline and a fine hypodermic needle.The needle is then changed and, using Gabriel's method, the ischio-rectalfossa on either side of the anal canal is infiltrated with I0ccs. of anaestheticsolution. In addition, 2 per cent. Xylocaine Gel or 10 per cent. Decicaineointment should be introduced into the anal canal, and at least fiveminutes must elapse before the operation is commenced.

OperationThe patient is now placed in the left lateral position and a bivalve

Ricord's speculum introduced. The blades of the speculum are graduallyopened, thus putting the internal sphincter on the stretch. When there ismuch fibrosis present the blades of the speculum can only be partlyopened until the lowest part of the sphincter has been divided. Thcblades will now usually open with ease. During the opening of thespeculum the patient experiences a desire to defaecate and, to allay thepatient's fears, this should be explained beforehand.The circular fibres of the internal sphincter are completely divided to

just above the dentate line, exposing the smooth surface of the conjointlongitudinal muscle underneath. The wound should be carried outwardsa short distance into the perianal skin and any well-developed commissuralfibres of the subcutaneous external sphincter at the anal margin dividedto avoid any " ridge " (Fig. 16 a, b and c).

Bleeding is usually only slight, and ooze which may obscure the anatomycontrolled by pressure with a gauze swab, moistened with 1/1,000 adrenalin,on the operative field. Small polypi and skin tags should be excised.At the end of the operation, a small piece of Oxycel gauze is placed

directly upon the wound and the corner of a gauze swab, moistened in21 per cent. Milton solution, is inserted into the anal canal. Dressings arekept in place by a T-bandage. The patient should rest for half an hourand the dressings finally inspected for bleeding just before the patientleaves hospital.

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Post-operative careA patient operated on in the morning returns home to bed, taking two

Compound Codeine tablets. The same evening, to ensure a comfortablenight, Pethidine 100mgms. is taken by mouth and in the early morning afurther two Codeine tablets may be required.

The next day the patient may be ambulatory and should take half anounce of liquid paraffin night and morning with the object of having abowel action on the following day.

After a bowel action the patient has a bath and the dressing, consistingof a gauze swab moistened with 2- per cent. Milton solution, is tuckedinto the anal canal and maintained in place with the T-bandage.

On the fifth post-operative day, a St. Mark's Hospital dilator is passedand, thereafter, twice a day until the fissure is healed. During the healingperiod, the patient should take phenobarbitone grs. i, three times a day.It is advisable to take a week off work but many patients who run a " oneman business" are back again in three days.

Healing can be expected in fourteen to twenty-one days, but during thehealing period the wound is relatively painless. Unless a long enoughdrainage incision is made posteriorly an area of exuberant granulationwill develop inside the anal canal which, although painless, will give riseto bleeding, discharge, and perianal irritation. These granulations canbecome very indolent but will heal after a few applications of a silvernitrate stick.

If the fissure is situated anteriorly, the internal sphincter should bedivided in the left posterior quadrant. It is a mistake to make a woundin the mid-line anteriorly, especially in women, as a wound in this positiondoes not heal well.

The relief of pain following sphincterotomy, though an open wound isleft in the anal canal, is dramatic. It is suggested that some of the painexperienced by a patient suffering from a fissure-in-ano may be initiatedin the spastic internal sphincter itself, in much the same way as painelsewhere occurs when plain muscle fails to relax. A visceral muscle iscapable of prolonged and constant spasm whereas a somatic musclequickly tires.

Lastly, we would draw attention to a still common error in conceptionof the anorectal musculature. This is still spoken and written of as tworings of muscle, one superimposed upon the other, the external sphincterbeing the most caudally placed muscle ring at the anal margin, the oneabove, the internal sphincter. Division of the latter, it is still often stated,will result in rectal incontinence. In fact, the relationship of the internalsphincter to the external group of sphincter muscles is that of one circularmuscle tube within another.

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The anorectal ring, which is formed posteriorly and laterally by thespecialised puborectalis portions of the levatores ani muscles and anteriorlyby the deep part of the external sphincter muscle as well as the corre-sponding parts of the longitudinal and circular muscle coats of the bowel,is at the level of the deepest part of the external sphincter muscle. Thisring, as described by Milligan and Morgan, can be located by palpationand is seen closing over the proctoscope as it is withdrawn from therectum into the anal canal. It is division of this anorectal ring whichleads to rectal incontinence. The internal sphincter may be divided, asdescribed, with little or no appreciable difference to anorectal control.

Gorsch (1941) writes of the anorectal musculature:" Anatomic dissections, particularly in this difficult situation, will depend

very much on a preconception of a trilaminar or bilaminar arrangement of theentire external sphincter and 'wishful' anatomy may unwittingly confuse theactual anatomic arrangement of the subject to hand."We have endeavoured, therefore, in this paper to demonstrate and

identify the landmarks which can be appreciated by sight and touch.These landmarks can be verified by anatomical dissection and microscopyand at operation.The name of Campbell Milligan, Consulting Surgeon to St. Mark's

Hospital, will be forever remembered for research into the anatomy ofthe anorectum; we pay tribute to him for his unwavering search for thetruth in this and in all things and for his inspiration, guidance andencouragement.

SUMMARY

(1) A new description of the anatomy of the anal canal is presented.

(2) The visible interhaemorrhoidal depression is described: it does notcoincide with the palpable anal intermuscular depression.

(3) The varying relationships of external to internal sphincters aredetailed and corrections made in the naming of anatomical details inprevious observations on fissure-in-ano and in the St. Mark's Hospitalhaemorrhoid operation.

(4) The internal sphincter and pecten band are identical structures.The anatomical name should be retained and the term " pecten band"should not be used in descriptive proctology.

(5) Attention is drawn to a common error in conception of anorectalmusculature.

ACKNOWLEDGMENT

We would like to thank Mr. R. N. Lane for his patience and perseverancein preparing the illustrations.

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REFERENCES

ABEL, L. (1932) Lancet 1, 714.EISENHAMMER, S. (1951) S. Afr. med. J. 25, 486.ELLIS, G. V. (1878) Demonstrations of Anatomy, 8th edition, London: Smith, Elder,

p. 420.FINE, F., and LAWES, C. H. W. (1940) Brit. J. Surg. 27, 723.GOLIGHER, J. C., LEACOCK, A. G., and BROSSY, J.-J. (1955) Brit. J. Surg. 43, 51.GORSCH, R. V. (1941) Perineo-Pelvic Anatomy, New York, p. 61.INBERG, K. R. (1952) Acta. chir. scand. 104, 4.MILES, E. W. (1919) Surg. Gynec. Obstet. 29, 497.

-- (1939) Rectal Surgery, London: Cassell, p. 138.MILLIGAN, E. T. C., and MORGAN, C. N. (1934) Lancet, 2, 1150 and 1213.-___________ - et al. (1937) Lancet, 2, 1 119.-____________- (1942) Proc. Roy. Soc. Med. 36, 367.PARKS, A. G. (1954) Proc. Roy. Soc. Med. 47, 997.SPIESEMAN, M. G. (1938) Amer. J. Surg. 42, 356.STROUD, B. B. (1896) Ann. Surg. 24, 1.WILDE, R. F. (1949) Brit. J. Surg. 36, 279.

THE BUCKSTON BROWNE DINNER

THE BUCKSTON BROWNE Dinner of Fellows and Members was held in theGreat Hall of the College on 1 1th July, 1956. Sir Harry Platt, the President,was in the Chair and those present numbered 175, including Fellows andMembers of the College and several distinguished visitors. It was a dinnerjacket occasion, befitting the " family party " of the College. As iscustomary, the College plate was conspicuous on the tables, a high placeof honour being given to the Riddell Cup, a large silver-gilt loving cuppresented to the College in 1932 by Lord Riddell in memory of SirBuckston Browne's only son, Lt. Col. George Buckston Browne, D.S.O.,who fell in the First World War. Among the toasts was a silent tribute tothe memory of the donor.The highlight of the occasion was a most generous gift. This was

announced by Sir Archibald McIndoe, Chairman of the FinanceCommittee, who said that Sir Simon Marks had joined the great band ofbenefactors of the College and had given him a cheque for £7,500, the firstof seven instalments of a gift of £52,500. The cheque was handed to thePresident, who then read the letter enclosing it as follows:

THE SIMON MARKS CHARITABLE TRUST9th July 1956.

DEAR SIR HARRY,At a meeting of the Trustees of this Charity held on Friday, 7th July, it was

decided to donate £52,500, spread equally over seven years, to the College fora " Simon Marks Research Fund" to provide money for research to be carriedout in the Departments of Anatomy, Pathology and Physiology, or any of them;the subjects of research to be selected from time to time by the Council of theCollege, with the object of increasing knowledge of the sciences related to surgeryand of elucidating surgical problems of current importance.

I have pleasure in enclosing herewith the cheque for the first annual payment.Yours sincerely,

SIMON MARKS.

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