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Home , Anal canal, Anal valves, Anus, Muscularis mucosae, Muscular layer, Sphincter

SURGICAL OF THE with special reference to the SURGICAL IMPORTANCE OF THE INTERNAL AND CONJOINT LONGITUDINAL MUSCLE by 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 when statements and facts do not accord, then business is not properly executed." Confucius THE DESCRIPTION BY Milligan and Morgan (1934) of the surgical anatomy of the anal canal with reference to -in-ano and that of Milligan et al. (1937), on the treatment of haemorrhoids, is essentially correct for the normal anal canal when examination is carried out without anaesthesia. The fact, however, that the relationship of the anal musculature altered under anaesthesia was not realised and resulted in the misnaming of the internal sphincter. At operations for haemorrhoids and fissure-in-ano, this muscle in the original descriptions was confused with the subcutaneous external sphincter. Division of the internal sphincter muscle (sphincterotomy), described by Eisenhammer (1951), for " Chronic Internal Anal (Sphincteric) Contracture" re-focused our attention, at St. Mark's Hospital, on the exact position of the internal sphincter. The work of Fine and Wickham Lawes (1940), Wilde (1949) and, more recently, Parks (1954), together with the co-operative investigations over several years by the Surgical Staff at St. Mark's Hospital (Goligher et al., 1955), now enables a more accurate description 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 of Morgagni (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 passes through the pelvic visceral aperture- the anorectal ring-to the the anal margin. This concept of the anal canal is more apposite for surgical] purposes and as the anorectal ring is above the valves of Morgagni, the surgical anal canal is longer than its anatomical counter- part (Fig. 1).

Anorectal rin (pelvic viuceri aperture)

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 of the rectum extends down- wards from the anorectal ring into the anal canal and overlies the upper half or two-thirds of the internal sphincter. It is loosely attached to the underlying structures and covers the internal haemorrhoidal plexus. As it approaches the level of the columns of Morgagni, the columnar mucous membrane becomes cuboidal, is darker in colour, and, just above the 89 C. NAUNTON MORGAN AND HENRY R. THOMPSON

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Anorectal 4. , ring (pelvic visceral o i u Rectal aperture) 9X, mucosa ... . . I *.~~~v*~ (pink) . - .Ana Conjoint mucosa longitudinal (re. Anal

sphncltalerExternal fMran,bcmslmcluev t hr it coer ansofcoloured) sphincter c On , this region of the a~ ~~~~~nalpoet canal iteit h analhvalves of Morgagni, becomesr plum colouredawhereitcorsthe mecaol in mnatson the in lhaemorroid an eis no k nathe AaMe o. Onprctescopy etheirio of n the analpcanal a into The instrument2.unFig. the iingsuoferthedceofotanalhcanal,aninterlhaemorotbth anlmscuatuiregua.wvidal p sin

cuaeptiblAthert inoteloeanal vvs, thellicninhce ncangesfmoimne orgtd trueansskino epithbelwiuand athte lfeine dsthe analcanal tontsq moustfalettheli tahs latterchantgre althamouhoab t es not Take paoneAnas reular in aproutn thea thcirmerenceof the bwl,butaasaoes irreg wyatv Thersubmucou spaiflcle. ,seto uosgad,adi assipr Therelattre nohairefltolliles swatruor muous glnds,tanditac passes imeglr- cepctiblyTahesamonalineto theloose,digthickeroandopigentedinepithe lining chasgeentrce analcorrugthedcanal skintruetskinTansitions. of nd,of theparcentn colthe deliaes,tesmr ot, tus aen htwin. analpcahalmJpthlustIthabelowferdoa the dentateline.teaaaalsisms fecirml attahed jntionthdeeper structures-Hilton'swheitheline. Thet zonte betweenth deTate lineandu eptheliadhernghabentclehanal canalskin.wsdsrbdbSTroud Owtilyingto the loose,attachmentaof thgenmucos coveringae thue sinterna hdnatemorrhoindalpeubvthe tetheredtanal canal skin esrbdan theStloose attachment of the skin over the external haemorrhoidal plexus below, two potential spaces are formed. They are the submucous space which is 90 SURGICAL ANATOMY OF THE ANAL CANAL situated above the level of the (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, 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 from the subjacent tissues at this site (Parks). The true skin of the and anal canal skin cover the external haemorrhoidal plexus. Short connecting vessels pass upwards under the smooth 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. 91 8 C. NAUNTON MORGAN AND HENRY R. THOMPSON The lining of the anal canal above the anal valves is insensitive except to stretching, such as by rapid injection of an internal haemorrhoid, whereas the anal canal skin and the true skin of anus are extremely sensitive to painful stimuli. To summarise-the surgical anal canal is lined from above downwards by pink rectal mucosa (columnar ) covering the haemorrhoidal pedicle at the anorectal ring; by dark red anal mucosa (cuboidal and transitional epithelium) covering the main haemorrhoidal mass; by smooth, 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 ) covering the external haemorrhoid. THE ANAL MUSCULATURE The 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 the pelvic diaphragm and its termination can be felt just within the anal orifice. Its position and relation to other structures of the anal canal and its 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 rectum together with fibres from the puborectalis muscles. As this thickened conjoint muscle passes downwards between the internal sphincter and the external 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 its muscular fasciculi, to enter the submucous space. This is most clearly shown 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 portion of the internal sphincter. In this situation, the of the bowel is much thicker and the longitudinal " muscle " fibres apparently pass into it. Fine and Wickham Lawes (1940), have called this sub- mucous fibro- the musculus submucosae ani. In this region (pecten) the anal canal skin is attached to the subjacent fibro-muscular layer and indirectly, therefore, to the lower portion of the internal sphincter (Fig. 5). This attachment of the longitudinal muscle to the lining of the anal canal separates the submucous from the subcutaneous perianal space. It should be noted that the perianal space extends upwards within the anal canal for a short distance and that the thickened lower end of the internal sphincter lies within this subcutaneous space. 92 SURGICAL ANATOMY OF THE ANAL CANAL

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(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 muscle loop 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 external sphincter. This insertion is obtained by fanning out of the longitudinal fibres which then pass through the circular fibres of the subcutaneous 93 8-2 C. NAUNTON MORGAN AND HENRY R. THOMPSON external sphincter. Some of these fibres lie immediately under the skin of 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 Subcutaneous external sphincter

Fig. 4b. Magnification of area marked on 4a. This shows fibres of the longitudinal 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, its fibres pass between the deeper portions of the external sphincter muscle (Wilde, 1949). Anteriorly, the longitudinal muscle fibres become attached firmly to the triangular , to the and to the apex of the and represent the recto-urethralis muscle. This attachment holds the rectum to these structures and may be identified during perineal dissection of the rectum. 94 SURGICAL ANATOMY OF THE ANAL CANAL

4 ~ - iRed rectal mucosa

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

.9.

Anal canal skin

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

Fig. 5. Longitudinal section of anal canal. The fibres of the longitudinal muscle passing 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 C. NAUNTON MORGAN AND HENRY R. THOMPSON

Fig. 6a. The visible inter-haemorrhoidal depression. By virtue of its wide attachments, the conjoint longitudinal muscle forms an important integral part of the anorectal musculature. Since the bulk 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 (perianal space) below are loose and project. Thus the fixed portion of the anal canal lining is seen as a depression on a prolapsing haemorrhoid. This depression in fact separates the internal haemorrhoidal plexus (internal haemorrhoid) from the external haemorrhoidal plexus (external haemorr- hoid) and is an inter-haemorrhoidal depression. When a second degree 96 SURGICAL ANATOMY OF THE ANAL CANAL 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 subcutaneous external sphincter muscle and the lower border of the internal sphincter muscle (the thickened innermost portion of the circular muscle coat of the rectum), a distinct depression is palpable. This depression has been called by Milligan and Morgan the anal intermuscular depression and in previous descriptions was considered to coincide with the attachment of the intermuscular septum (one of four fibro-muscular expansions of the longitudinal muscle) to the lining of the anal canal. It is, however, not possible to demonstrate such a direct attachment of the longitudinal muscle to the anal lining.

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11-. maw,, KM \ Wh.'l`444

Fig. 6b. The palpable intermuscular depression. 97 C. NAUNTON MORGAN AND HENRY R. THOMPSON The visible interhaemorrhoidal depression is distinct from the palpable anal intermuscular depression and bears no fixed relation to this landmark (Figs. 6a and b). It has always been difficult to understand why infection so readily passes through such a relatively stout muscle as the internal sphincter, or through or between the external . The fact that fibres of the

Fig. 7a. Diagram of intermuscular abs- Fig. 7b. Fistula resulting from inter- cess indicating possible paths of spread. muscular abscess. longitudinal muscle pass both inwards through the internal sphincter and also outwards between portions of the external sphincter muscles most probably accounts for the routes by which infection extends directly from the anal canal into the perianorectal tissues to form an abscess or fistula- in-ano. Conversely, it would explain how an abscess, which takes the line of least resistance along a fascial plane or other anatomical pathway, may track from the ischio-rectal space along the fibres of the longitudinal muscle in between the fasciculi of both the external and internal sphincter muscles to burst into the anal canal. It is not uncommon to find an abscess or a fistula extending upwards between the internal and external sphincter muscles. This extension must occur along the main portion of the longitudinal muscle. Such an abscess 98 SURGICAL ANATOMY OF THE ANAL CANAL displaces the external sphincter group outwards away from the internal sphincter and may enter the anal canal at any level by extending through the internal sphincter along a fasciculus of the longitudinal muscle. The fistula resulting from such an abscess will require division of a portion of the internal sphincter alone to cure it; the external sphincter muscle is left intact (Figs. 7a and b). The multiple extensions of the longitudinal muscle through the internal sphincter may also explain the not uncommon occurrence of more than one internal opening. Failure to appreciate this possibility and to identify a second internal opening, is one of the reasons for persistence of a fistula after surgical treatment. ANATOMICAL RELATIONSHIPS OF THE INTERNAL AND EXTERNAL SPHINCTER ANI MUSCLES The relative positions of the lower portion of the internal sphincter and the subcutaneous external sphincter may be altered. The changes in 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 anatomy These are found in both the subcutaneous external and the internal sphincter. The former usually consists of an annular band of commissural fibres but these commissural fibres may be replaced by slips of muscle fibres passing down on their respective sides to become continuous with the superficial portion of the external sphincter (Gorsch). The anal intermuscular depression in such subjects is felt posteriorly as a deep pit into which the tip of the finger may be inserted. In rare instances the anus projects from the in a conical manner. This can be shown to be due to an elongated hypertrophied internal sphincter. On inserting the finger into the anus, no anal inter- muscular depression is felt since the subcutaneous external sphincter encircles the base of the projection and any palpable depression is situated 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 the relative size and position of the internal and external sphincter muscles is in any way related to function and pathology. (b) The effect upon the sphincter of lateral traction on the perianal skin Continuous lateral traction on the perianal skin during examination may cause the external sphincter to dilate slowly. This dilatation also occurs in the lithotomy position when the perianal skin is again drawn 99 C. NAUNTON MORGAN AND HENRY R. THOMPSON taut laterally. The phenomenon is reproduced when squatting to defaecate and 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 the subcutaneous external sphincter, contracts and draws up this relaxing muscle over the faecal bolus. This everts the anal canal and changes temporarily the relationship of the subcutaneous external sphincter and the internal sphincter. (b)

Right buttock externaleSubcatsneoussphincter

/O~Internal sphlincter

p 0 A N T T R R

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 lateral position 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 SURGICAL ANATOMY OF THE ANAL CANAL (c) Effects of anaesthesia on sphincter tone The anal canal is opened and closed by the synergistic action of both somatic and visceral muscle, although the exact mechanism as yet is incompletely understood. Inberg of Helsinki (1952) has shown that following the intravenous injection of tetraethylammonium chloride, in order to block the supply to , the tone of the internal sphincter is diminished. The combined sphincter tone, however, is increased for a period due to compensatory contraction of the external sphincter. 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 is said not to relax even when the patient is deeply anaesthetised. It is, however, unreasonable to suppose that the external sphincter differs from the remaining 519 voluntary muscles of the in its reaction to anaesthesia. As a matter of fact, it is just as susceptible to anaesthesia as any of the others, but it is incapable of becoming relaxed on account of the constricting effect of the pecten band. When the pecten band has been divided it is found that the external sphincter relaxes under the influence of anaesthesia just like any other voluntary muscle. It is not possible to stretch the pecten band. Consequently, if forcible dilatation 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 has become fibrosed, as in haemorrhoids or fissure-in-ano, it may indeed require 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 the internal 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 the anorectal ring to the anal verge, before and during anaesthesia, shows that on relaxation ofthe anorectal musculature the anal canal may be shortened by 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 down well below the subcutaneous external sphincter (Fig. 10 a, b and c). Because this change in muscle relationship was not appreciated, the internal sphincter has been erroneously labelled the subcutaneous external sphincter in descriptions of the St. Mark's operation for haemorrhoids prior to 1955. The correction ofthis error in no way modifies the technique of the operation or the principles on which it is based. The description of the dissection of haemorrhoids at this operation should read: The blades of the scissors are placed, one at the muco-cutaneous junction and the 101 C. NAUNTON MORGAN AND HENRY R. THOMPSON other at the outer border of the external haemorrhoidal plexus. A V-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 the corrugator cutisani muscle (conjoint longitudinal fibres). The perianal space is now entered and the white circular fibres of the internal sphincter

Internal sphincter

Internal sphincter

Subcutaneous external sphincter I

Subcutaneous (a) external sphincter (b) Fig. 9. Showing the effect of anaesthesia on the relationship of the subcutaneous external and internal sphincter muscles. (a) Closed anus. (b) Anus relaxed under anaesthesia. muscle are exposed. The external haemorrhoid is dissected inwards with scissors and the internal sphincter muscle bared to its inner border. Here the fibres of the conjoint longitudinal muscle will be seen passing through the fasciculi of the internal sphincter into the dissected haemorrhoid. It is possible to slide or imbricate these fasciculi upon one another by traction on the dissected pile. Ligation of the mucosa of the pile pedicle and its vessels will incorporate the longitudinal fibres, so anchoring the pile pedicle to the internal 102 SURGICAL ANATOMY OF THE ANAL CANAL sphincter. This will prevent upward retraction of mucosa to its original site, thus obviating a large, raw area (Fig. 11 a, b and c). It is emphasised, therefore, that the prominent ring of white circular muscle exposed at the St. Mark's operation of haemorrhoidectomy is not the 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 operation of 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 terminal interphalangeal 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. ofthe left hand pressed the skin of the anus outwards. He claimed that this displaced the inner border of the external sphincter outwards, and by dividing the mucosa of the lower part of the anal canal, the pecten band was exposed (Fig. 12). Division of this band, pectenotomy, was the Miles operation 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 skin at the anal margin." He has subsequently described it (Miles, 1939) as a deposit of fibrous , circularly disposed in the of the part of the anal canal between 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's Hospital. Fine and Wickham Lawes (1940) expressed surprise that 103 C. NAUNTON MORGAN AND HENRY R. THOMPSON universal recognition had not been accorded by proctologists to its existence. Miles asserted that the pecten band did not occur in the healthy anal canal but Abel (1932) and Spieseman (1938) agreed that a pecten band might exist without any associated pathology in the anorectum. Fine and Wickham Lawes (1940), were of the opinion that Miles and Abel (1932), influenced by the physical characteristics of the pecten band and the contrast ofits white fibres to the red fibres ofthe external sphincter, concluded it was of fibrous nature. The same authors demonstrated in four biopsy specimens of the pecten band, that all contained involuntary unstriped muscle fibre, and remarked that its pallor was quite compatible with 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, varying in thickness, seen in the healthy and diseased anorectum, consisting of *~~~~~~~~~~~~~~~~~~~~~~~~.... .:...... i;..,. .. ..-..

W Drawn down fasciculus of internal sphincter still covered by longitudinal fibres (a) (b) (c) Fig. 11. Dissection of the left lateral haemorrhoid at haemorrhoidectomy. (a) Skin divided, exposing corrugator cutisani muscle. (b)iIncision deepened, exposing lower border of internal sphincter muscle. (c)IWith wider skin cut, both internal and external sphincter divided. (See Figs. 12 and 13.) 104 SURGICAL ANATOMY OF THE ANAL CANAL

.. ? I

Fig. 12. The linear incision through the anal skin gapes widely, exposing A, the pecten 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.part oftheana_l canalis everted to.render.prominent.the pecten..band whichisdivided

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.i:: ...... ':':: . .. i.e§4;}| ~~~~~~~~~~~~~~...... 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, after dividing the longitudinal fibres of the corrugator cutisani muscle, exposes the internal sphincter and the subcutaneous external sphincter. Miles in fact called the fibrosed internal sphincter muscle the pecten band (see Fig. 11) (These two figures are taken from Miles Rectal Surgey (1939) by permission of Mrs. Ernest Miles and Cassell & Co London) 105 C. NAUNTON MORGAN AND HENRY R. THOMPSON circularly disposed unstriped muscle fibres, division of which cures a fissure-in-ano. This corresponds closely to the description of the internal sphincter muscle as recognised at St. Mark's Hospital, except to add that superiorly it is continuous with the circular muscle coat of the bowel and that externally lies the main portion of the conjoint longitudinal muscle. 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 acute fissure in ano. fissure with longitudinal fibres in floor of fissure. cannot be seen unless the anus is everted. Pain and muscular spasm are such that this cannot be readily achieved without a surface or other anaesthetic. A fissure does not extend upwards above the muco-cutaneous junction where, at its apex, an anal papilla is frequently present. It does extend downwards to the true skin of the anus, where inflammatory changes lead to the formation of the tell-tale skin tag or sentinel pile and Milligan (1942) has suggested that fissure-at-anus is as correct a term as fissure-in-ano. In an acute fissure, when only the anal canal skin is broken, radiating longitudinal fibres will be seen in the floor of the fissure; these unstriped muscle fibres are derived from the fibres of the conjoint longitudinal muscle which have traversed the lower end of the internal sphincter. Some of the longitudinal fibres passing through the innermost portion of the subcutaneous external sphincter may also be exposed (Fig. 14a and b). When a fissure has become chronic the longitudinal fibres disappear and 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 a personal. experience (H.R.T.) of 300 operations for , which has been confirmed by our surgical colleagues at St. Mark's Hospital, 106 SURGICAL ANATOMY OF THE ANAL CANAL it has been shown beyond doubt that division of these white circular fibres relieves the pain and results in the healing of a fissure-in-ano. From anatomical dissections and biopsies made at the time, it can be categorically stated that they are unstriped muscle fibres of the internal sphincter ani muscle. In the course of this investigation, Miles' method of everting the anal canal has been practised many times. It has always resulted in displacing the subcutaneous external sphincter outwards and in bringing down the lower 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, once seen, it is impossible to confuse them. The internal sphincter is composed of fine, closely packed, white fibres, whilst the subcutaneous external sphincter consists of coarser, loosely packed, reddish brown fibres. A recent clinical assistant at St. Mark's Hospital, H. J. Hambury, most aptly described the difference in appearance as that between the meat of the breast and leg of a chicken. Patients sometimes tolerate a fissure for months and even years. In such cases fibrotic changes will most certainly occur in the internal

Fig.15. Chronicfissre Longitudinalmusclefibreshaveulcerated..through... . 2z...... i 2 '2j,-

...... , - 3.wE.j_a

Fig.15. Chronic fissure. Longitudinl mucl fire have...... ulertd houh

exposing the white circular"JIsX|~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~.....fibres of the internal...... sphincter muscle. sphincter, forming as it does the floor and base of a chronic ulcer. This results in a rigid contracture at the anus into which it is difficult and painful to pass an index finger. Indeed, in cutting through the tough fibres of the internal sphincter in a long-standing fissure, a grating 107 9 C. NAUNTON MORGAN AND HENRY R. THOMPSON

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

Fig. 16b. Internal sphincter muscle partly divided.

Fig.`7 16c. Internal sphincter muscle divided, exposing underlying longi- tudinal muscle sheet. Skin tag and polyp removed. Commissural fibres of the subcutaneous external sphincter muscle when well developed require to be divided to prevent a "ridge." 108 SURGICAL ANATOMY OF THE ANAL CANAL sensation can be felt. It is only when they are divided that any elasticity returns 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 in elderly people and has been referred to as senile anal stenosis. It is also associated with the prolonged use of aperients, especially medicinal paraffin, which results in the passage of fluid or unformed stools. There are two possible explanations for the occurrence of in the internal sphincter without an obvious anal lesion. Firstly, fibrosis may be due to recurrent minor trauma caused by the passage of large, constipated stools, alternating with fluid stools, from the habitual misuse of purgatives. Thus the internal sphincter is either grossly overstretched or inadequately dilated. Secondly, as Miles has suggested, fibrosis may result from venous congestion 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 be divided. Fine and Wickham Lawes commented on a variation in the amount 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 to demonstrate both structures in the same patient or the same anatomical dissection. Reference to the internal sphincter, whether fibrosed or not, as the " pecten band " should therefore cease and, except for historical interest, should not find a place in proctological literature. This correction in nomenclature, however, in no way detracts from the value and importance of Miles' operation of pectenotomy which is, in fact, an internal sphincterotomy. (e) Positional sphincter changes in certain pathological states Internal haemorrhoids prolapse owing to the laxity of the subcutaneous external sphincter muscle, overstretching of the conjoint longitudinal muscle fibres and, finally, weakening of the attachment of the anal canal skin to the subjacent tissue, including the lower end of the internal sphincter. When this latter anchorage is strained, the interhaemorrhoidal depression may be seen externally. It becomes less obvious, and eventually may be obliterated, in large third degree haemorrhoids (Fig. 6a.). Simultaneously with the overstretching of the subcutaneous external sphincter, the longitudinal muscle also becomes stretched and no longer adequately supports the anal musculature. It is likely that the bracing effect of its fibres passing through the subcutaneous external sphincter muscle is lost and this sphincter no longer remains in close relation to the anal orifice. The distal end of the internal sphincter will now be at a comparatively lower level and may surround the anal orifice and actually be more caudally placed than the subcutaneous external sphincter. Under 109 9-2 C. NAUNTON MORGAN AND HENRY R. THOMPSON these circumstances the anal canal is shortened and the anal canal skin and the interhaemorrhoidal depression are visible at the anal verge. By pulling the perianal skin outwards on either side with the fingers, the lower end of an internal haemorrhoid may protrude or, on rare occasions, should the internal sphincter relax, the whole anal canal or even the lower rectum may be seen. (f ) Distortion in anatomical dissections and microscopical preparations of the anal canal In removed from the cadaver for anatomical dissections, muscle relationships are distorted because their attachments are severed and the internal sphincter can invariably be demonstrated at the anal margin. When making longitudinal sections of the rectum for micro- scopic study, the tissues become stretched, exaggerating and distorting the relations seen in living anatomy. DIVISION OF THE INTERNAL SPHINCTER (INTERNAL SPHINCTEROTOMY) The fibres ofthe internal sphincter may be ruptured by forcible stretching under anaesthesia (Recamier), they may be divided, after everting the anal canal and identifying the internal sphincter by palpation (Miles), or an anatomical dissection and section of the internal sphincter may be made under direct vision. In comparison with the first two methods, section of the internal sphincter under direct vision is to be commended for the precision and accuracy with which it can bE carried out. In the past, at St. Mark's Hospital, the fashioning of a drainage wound was included in the operation. The patients were admitted to hospital for a minimum period of three weeks. Now we believe that the cure of a fissure can be achieved in the majority of cases by dividing the internal sphincter 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 emphasised that the same care required for major must be applied to all minor operations upon the anal canal. Selection of patients Some patients are temperamentally unsuited for any operation under local anaesthesia, however well this may be given. Further, the fissure may be complicated by a chronic abscess, a fistula, a large polyp and skin tag; or the patient's home may be remote from the hospital. It is better to admit these patients to hospital and perform the operation under thiopentone anaesthesia. If the operation is performed as an out-patient procedure, the patient should always be accompanied by a relative or friend 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 the presence of large haemorrhoids, the haemorrhoids will prolapse and 110 SURGICAL ANATOMY OF THE ANAL CANAL thrombose and the patient's discomfort will be increased instead of being relieved. A patient with haemorrhoids and fissure should be admitted to hospital, a haemorrhoidectomy performed, and the internal sphincter formally divided in the wound of the left lateral haemorrhoid. A small or moderate sized haemorrhoid in the right anterior position may be injected with 5 per cent. Phenol in almond oil at the time of a sphinctero- tomy as an out-patient. Preparation The patient is advised to empty the bowel on the morning of operation. The perianal skin is shaved and prepared with Cetavlon and spirit. Anaesthesia With the patient in the right lateral position, an intradermal weal is raised in the mid-line posteriorly, one inch from the anal margin, using 2 per cent. Xylocaine with and a fine hypodermic needle. The needle is then changed and, using Gabriel's method, the ischio-rectal fossa on either side of the anal canal is infiltrated with I0ccs. of anaesthetic solution. In addition, 2 per cent. Xylocaine Gel or 10 per cent. Decicaine ointment should be introduced into the anal canal, and at least five minutes must elapse before the operation is commenced. Operation The patient is now placed in the left lateral position and a bivalve Ricord's speculum introduced. The blades of the speculum are gradually opened, thus putting the internal sphincter on the stretch. When there is much fibrosis present the blades of the speculum can only be partly opened until the lowest part of the sphincter has been divided. Thc blades will now usually open with ease. During the opening of the speculum the patient experiences a desire to defaecate and, to allay the patient'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 conjoint longitudinal muscle underneath. The wound should be carried outwards a short distance into the perianal skin and any well-developed commissural fibres of the subcutaneous external sphincter at the anal margin divided to avoid any " ridge " (Fig. 16 a, b and c). Bleeding is usually only slight, and ooze which may obscure the anatomy controlled 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 in 21 per cent. Milton solution, is inserted into the anal canal. Dressings are kept in place by a T-bandage. The patient should rest for half an hour and the dressings finally inspected for bleeding just before the patient leaves hospital. 111 C. NAUNTON MORGAN AND HENRY R. THOMPSON Post-operative care A patient operated on in the morning returns home to bed, taking two Compound Codeine tablets. The same evening, to ensure a comfortable night, Pethidine 100mgms. is taken by and in the early morning a further two Codeine tablets may be required. The next day the patient may be ambulatory and should take half an ounce of liquid paraffin night and morning with the object of having a bowel action on the following day. After a bowel action the patient has a bath and the dressing, consisting of a gauze swab moistened with 2- per cent. Milton solution, is tucked into the anal canal and maintained in place with the T-bandage. On the fifth post-operative day, a St. Mark's Hospital dilator is passed and, thereafter, twice a day until the fissure is healed. During the healing period, 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 " one man business" are back again in three days. Healing can be expected in fourteen to twenty-one days, but during the healing period the wound is relatively painless. Unless a long enough drainage incision is made posteriorly an area of exuberant granulation will develop inside the anal canal which, although painless, will give rise to bleeding, discharge, and perianal irritation. These granulations can become very indolent but will heal after a few applications of a silver nitrate stick. If the fissure is situated anteriorly, the internal sphincter should be divided in the left posterior quadrant. It is a mistake to make a wound in the mid-line anteriorly, especially in women, as a wound in this position does not heal well. The relief of pain following sphincterotomy, though an open wound is left in the anal canal, is dramatic. It is suggested that some of the pain experienced by a patient suffering from a fissure-in-ano may be initiated in the spastic internal sphincter itself, in much the same way as pain elsewhere occurs when plain muscle fails to relax. A visceral muscle is capable of prolonged and constant spasm whereas a somatic muscle quickly tires. Lastly, we would draw attention to a still common error in conception of the anorectal musculature. This is still spoken and written of as two rings of muscle, one superimposed upon the other, the external sphincter being the most caudally placed muscle ring at the anal margin, the one above, the internal sphincter. Division of the latter, it is still often stated, will result in rectal incontinence. In fact, the relationship of the internal sphincter to the external group of sphincter muscles is that of one circular muscle tube within another. 112 SURGICAL ANATOMY OF THE ANAL CANAL The anorectal ring, which is formed posteriorly and laterally by the specialised puborectalis portions ofthe levatores ani muscles and anteriorly by 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. This ring, as described by Milligan and Morgan, can be located by palpation and is seen closing over the proctoscope as it is withdrawn from the rectum into the anal canal. It is division of this anorectal ring which leads to rectal incontinence. The internal sphincter may be divided, as described, 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 the entire external sphincter and 'wishful' anatomy may unwittingly confuse the actual 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 microscopy and at operation. The name of Campbell Milligan, Consulting Surgeon to St. Mark's Hospital, will be forever remembered for research into the anatomy of the anorectum; we pay tribute to him for his unwavering search for the truth in this and in all things and for his inspiration, guidance and encouragement. SUMMARY (1) A new description of the anatomy of the anal canal is presented. (2) The visible interhaemorrhoidal depression is described: it does not coincide with the palpable anal intermuscular depression. (3) The varying relationships of external to internal sphincters are detailed and corrections made in the naming of anatomical details in previous observations on fissure-in-ano and in the St. Mark's Hospital haemorrhoid 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 anorectal musculature. ACKNOWLEDGMENT We would like to thank Mr. R. N. Lane for his patience and perseverance in preparing the illustrations. 113 C. NAUNTON MORGAN AND HENRY R. THOMPSON 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 the Great Hall of the College on 11th July, 1956. Sir Harry Platt, the President, was in the Chair and those present numbered 175, including Fellows and Members of the College and several distinguished visitors. It was a dinner jacket occasion, befitting the " family party " of the College. As is customary, the College plate was conspicuous on the tables, a high place of honour being given to the Riddell Cup, a large silver-gilt loving cup presented to the College in 1932 by Lord Riddell in memory of Sir Buckston 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 to the memory of the donor. The highlight of the occasion was a most generous gift. This was announced by Sir Archibald McIndoe, Chairman of the Finance Committee, who said that Sir Simon Marks had joined the great band of benefactors of the College and had given him a cheque for £7,500, the first of seven instalments of a gift of £52,500. The cheque was handed to the President, who then read the letter enclosing it as follows: THE SIMON MARKS CHARITABLE TRUST 9th 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 for a " Simon Marks Research Fund" to provide money for research to be carried out 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 the College, with the object ofincreasing knowledge of the sciences related to surgery and of elucidating surgical problems of current importance. I have pleasure in enclosing herewith the cheque for the first annual payment. Yours sincerely, SIMON MARKS. 114