Volume 68 November 1975
21
681
Section of Proctology President Alan G Parks Mch
Meeting 27 November 1974
President's Address Anorectal incontinence
Anatomy and Physiology The anorectal region is composite in its embryological origin; it consists of the termination of the alimentary viscus, surrounded by the external sphincters which are of somatic origin. In Fig 1 an attempt is made to show how the visceral and somatic components are integrated. These may each be regarded as two tubes, one of which surrounds the other. The inner tube, being visceral, consists of mucosa, submucosa, circular and longitudinal muscle; it is innervated by the autonomic nervous system and is therefore not subject to voluntary control. The outer tube, composed of skeletal muscle, has the shape of a funnel, the upper part of which (the levator ani muscles) closes off the pelvic hiatus. In this way a complete pelvic -muscular diaphragm is formed, which counteracts the force of intra-abdominal pressure. The external sphincters play a major role in establishing normal continence. The dual origin of the anorectal mechanism makes this highly specialized region complicated from both the anatomical and physiological points of view.
by Alan G Parks Mch (The London Hospital, Turner Street, London El, and St Mark's Hospital, City Road, London ECI) The plight of a patient with frank fiecal incontinence is a very unhappy one indeed. There is the obvious association with uncleanliness and the feeling of being a social outcast. Suchaperson will not meet people, will not leave the house, or be able to do any shopping. If the situation is known to the family the patient may well be rejected as a result, especially in old age. It is indeed a very grave social problem, particularly with the elderly, and anything that will improve it is highly desirable. The frequency of the problem is greater than is generally realized, because patients will not discuss it and will not even tell their nearest relatives or their medical advisers. They manage to cope for some years by wearing a great deal of padding, but finally even this is of no avail.
~~~~Rectum E
>
S "
Longitudinal Muscle of Rectum
Internal Sphincter Longitudinal Layer of Anal Canal
Genito-Urinary Viscus
Fig 1 The anorectal mechanism isformedfrom two components, one visceral and the other somatic. The visceralpart comprises the termination ofthe hindgut and includes the internal sphincter and longitudinal muscles. It is surrounded by the skeletal muscle or somatic component, which is made up ofthe external sphincter muscles and the levator ani muscles. (Reproducedfrom Parks 1971a by kindpermission)
682 Proc. roy. Soc. Med. Volume 68 November 1975
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lower border of which usually reaches the anal margin, and it appears to be merely a thickened extension of the muscle of the lower rectum. Physiologically, however, it behaves entirely differently from circular muscle elsewhere. It exists in a continuously tonic state, because of which it is almost certainly responsible for maintaining closure of the resting anal canal. Distension of the rectum or lower colon will cause immediate relaxation of the muscle. This occurs even if an anastomosis is interposed between the stimulated colon and the sphincter. There is no doubt that at times a strong tonic internal sphincter can maintain continence, even with total external sphincter paralysis. In some elderly people in whom the external sphincters are weak, Fig 2 This diagrammatic coronal section through the the internal sphincter may be the main factor at pelvicfloor again emphasizes its two-component and if this is stretched (as in the treatment work, constitution. There is aplane ofcleavage, the of fissure) incontinence can occur. intersphincteric plane, between the viscus and the The external sphincter may be divided anatosurrounding external sphincter mass mically into several parts. From the surgeon's The physiological mechanism of the pelvic point of view, however, the muscle bundles form a floor is designed to accomplish two tasks: first to continuous sheet and there are no obviously convert a potential perineal colostomy into an separate components except for the lowest fibres. automatically functioning sphincter, and second As the muscle mass is traced upwards, the puboto resist the force of intra-abdominal pressure, rectalis component is reached. This is a strong which if unopposed, would inevitably produce a bundle of fibres that almost completes a circle by perineal hernia. The linkage of these two tasks is running from one half of the arch of the pubic a complex one; at times it breaks down, for ramus around and behind the rectum to the instance, when fiecal stress incontinence occurs in ramus on the other side. It is almost a sphincter certain pathological situations. A terminal anatomically, but it does not quite meet anteriorly; storage reservoir is provided by a capacious it encircles the terminal parts of all the pelvic rectum; a complex sphincter mechanism controls viscera, and functions as a powerful sphincter in the outflow of the reservoir. In addition, a sensory the uppermost part of the anal canal. By its mechanism is required so that an awareness of contraction it maintains the anorectal angle, which is of great importance in the maintenance of rectal filling reaches the conscious level. The visceral component of the anal canal is normal continence. The plane between the visceral component of lined in its upper part by columnar cell, mucussecreting endodermal epithelium. In the course of the anal canal and the external sphincters is an embryonic development, however, ectoderm embryonic interspace. It contains connective migrates into the lower half of the anal canal, tissue linking the two parts together, but very few which is therefore lined by stratified squamous blood vessels cross it, neither does any nerve epithelium. This type of mucosa does not secrete tissue. Its main importance is a technical one; dissection can be carried out in this plane quite mucus and is dry. If endodermal mucosa reached the lower anal canal, constant mucous leakage easily and without blood loss. The visceral would occur, causing perianal pruritus and other component can be separated from the external symptoms. The squamous mucosa is very sensitive sphincters over a wide area, and it is a most and is richly supplied with nerve filaments from useful approach to the pelvic cavity and to the the inferior heemorrhoidal nerves (Duthie & visceral surfaces of the skeletal muscles of the Gairns 1960). The rich innervation, which is pelvic floor. Above the level of the puborectalis, the origin somatic and not autonomic, has great significance of the other levator muscles passes backwards as it enables the mucosa of the lower anal canal to become an important sensory component of along the sides of the wall of the pelvis; anatothe mechanism of continence. The slightest mically they are separated by their site of origin stimulation of this mucosa causes reflex contrac- into two groups, the pubococcygeus, which is a tion of the external sphincters. strong bundle, and the iliococcygeus, which is The circular muscle of the rectum continues much the weaker component. They fan out to downwards into the anal canal as the internal form a funnel-shaped structure which closes the sphincter (Fig 2). It is a powerful muscle, the pelvic hiatus on either side of the midline. Despite
23
Fig 3 The levator ani musclesform a cradle in which the lower rectum is contained. Any pressure or volume change within the rectum is therefore transmitted to the muscles
the various labels given to the different portions of the pelvic floor muscles it should be stressed that they are essentially an anatomical and physiological unit. The nerve supply comes via branches of the pudendal nerve, which courses along the undersurface of the muscles and sends branches into them, finally reaching the external sphincter. No nerve supply of any significance enters this muscle mass from the pelvic aspect; this fact has surgical significance, to be discussed later. The levator muscles form a bed in which the lower rectum lies (Fig 3). About half the rectum is thus encircled, and any change in the rectal size will immediately exert pressure on the muscle surrounding it. Muscles which are actuated only voluntarily would be useless for the task of maintaining continence, as a person's attention would constantly have to be given to them; an automatic mechanism is essential. To achieve this the pelvic floor muscles are endowed with a special type of physiological activity. They are activated by a reflex mechanism and are constantly in a state of contraction. This is in marked contrast to other skeletal muscles, most of which are inactive at rest (Fig 4 A, B). There is a reflex arc made up of stretch receptors in the pelvic floor muscles themselves; an afferent neurone passes to the cauda equina and an efferent motor neurone in turn activates the muscle. Several workers have demonstrated the presence of muscle spindles in both the levator ani muscles and the anal sphincters. This reflex ensures not only that the muscles are constantly in action, but also that their activity increases with a rise in intra-abdominal pressure.
Section ofProctology
683
Thus when a person coughs, walks, laughs and so forth, the change in tension induced in the stretch receptors reflexly activates nerve fibres supplying the levator ani and sphincter muscles. In this way, every increase in abdominal pressure that tends to produce pelvic herniation is counteracted by an equal and opposite force. There is an interesting linkage between rectal distension and activity in the external anal sphincters. Distension of the rectal ampulla with a balloon containing, say, 50 ml of fluid will generally cause an excitation of the pelvic floor muscles with an increase in the basal tone. The mechanism of this linkage is of great interest and importance. It is known that the effect ceases above about 8 cm from the anal margin. It has previously been postulated that there are receptors in the wall of the rectum which act on the centres of the cauda equina to increase the activity in the motor neurones supplying the pelvic floor (Parks, et al. 1962). It was shown that this reflex did not depend on the presence of the rectal mucosa, because in patients who had had total excision of the rectal mucosa (for instance, for diffuse villous tumour of the rectum) the response was nevertheless present. After anterior resection, however, it was found that this response was present only below the anastomosis, not above it. This was regarded as strong evidence that receptors existed in the rectal wall itself. In the last three years, however, very low anastomoses have been performed, so that the colon is brought down to the upper anal canal. In these cases distension of the colon above the anal canal does give rise to the normal response in the external
Fig 4 Electromyographic recordings to show, A, that the extensor muscles of the forearm are totally inactive at rest, but develop intense electrical activity as the result ofsynergistic contraction (between T and R), whereas, B, the pelvicfloor sphincters have a constant activity
684 Proc. roy. Soc. Med. Volume 68 November 1975
24
extensive pelvic fibrosis due to infection, the sensation is normal and the patient is aware when the colon needs to be evacuated. The anal valve mechanism: It has always been supposed that the anal sphincters established continence purely by their squeeze effect; indeed, this may well be the case when voluntary contraction is called into play, but the maximal length of time for which this can be maintained is not much more than one to two minutes. Some years ago it was suggested (Parks et al. 1966) that there was a flap valve mechanism at the anorectal junction which depended on the rightangle between the axes of the lower rectum and the anal canal. Because of this, the mucosa of the lowest part of the anterior rectal wall lies across the upper end of the anal canal, which is kept closed by muscular action. This small segment of Fig 5 The valve mechanism at the anorectaljunction. anterior rectal wall is driven into the closed end Due to the angulation of the rectum with the anal of the canal by intra-abdominal pressure (Fig 5). canal, the lower part ofthe rectal wallforms a valve Every increase in intra-abdominal pressure will which occludes the closed upper anal canal. force the anterior rectal wall on to the canal and (Reproducedfrom Parks 1971a by kindpernussion) occlude the lumen; the greater the abdominal sphincter. It is therefore necessary to abandon the force, the more secure the occlusive effect. In order that defecation may take place, the view that the receptors for this reflex lie in the rectal ampulla; they are almost certainly situated valve mechanism must be unlocked. Intrain the levator ani muscles which, as mentioned abdominal pressure cannot ordinarily do this; a above, wrap themselves around the lower part of rise in intrarectal pressure must occur. Fecal matter subjected to intraluminal pressure will the rectum. Inhibition of sphincter tone also occurs during automatically lift the anterior rectal wall off the micturition and straining on defiecation. The upper anal canal. Once this has occurred, either latter is probably part of the normal mechanism intrarectal or extrarectal pressure will tend to of deftecation, as it allows the pelvic floor to drop expel the contents through the anal canal; only somewhat and causes complete sphincter relaxa- sphincter contraction can now prevent it. To summarize the present state of knowledge tion. However, if excessive defecation straining occurs in a constipated person, the pelvic floor is regarding the reflex mechanism of the pelvic forced downwards at the same time that all the floor, the afferent limb is derived almost entirely muscles are relaxed. They are therefore likely to from the skeletal muscles and from the squamous be passively stretched. Though recovery is almost anal mucosa. The same afferent end-organs certainly complete after a temporary episode of probably cause excitation or relaxation according this nature, if the habit persists for years, the to their frequency of response. The afferent repelvic floor may gradually descend, the pubo ceptors in the muscles are spindles; these have rectalis becomes stretched and the sphincters been demonstrated by several workers (Winkler 1958, Walls 1959). In the anal mucosa there are weakened. It is always difficult to discuss rectal sensation: numerous specialized sensory receptors; as far as like pain, it is impossible to define, and the feeling is known, there are no receptors in the rectum cannot be readily communicated from one itself which affect the skeletal muscle activity. person to another. There is no doubt, however, that in the normal person a full rectum is appre- Causes ofIncontinence ciated by a sense of pelvic floor discomfort which Traumatic muscle damage: The results of treatment is often associated with a sense of urgency. This of traumatic muscle section have been reported sensation can be very readily produced by elsewhere (Parks & McPartlin 1971) and will not distending the lower rectum with a balloon and, be discussed further in this paper. as discussed above, it is probably caused by filling of the rectum affecting the levator ani muscles Rectal prolapse: Porter, in his several articles on surrounding it. This is very important from the this subject (e.g. Porter 1962), has shown that the point of view of function after low anterior majority of patients with this condition have a resection. Provided that there has been no long history of defecation straining, and that two-
685
25
Section ofProctology
thirds are incontinent before the prolapse is treated surgically. In those patients who do improve following rectopexy, the tone of the anal sphincter is also objectively improved. Nevertheless, one-third remain incontinent following rectopexy and their situation is then very similar to that of the next group to be discussed, those suffering from idiopathic incontinence without prolapse, both physiologically and from the point of view of treatment.
There must be some primary defect in the neuromuscular anorectal mechanism to account for it. Many forms of treatment for idiopathic incontinence have been tried in the past. Faradism has given disappointing results. The Thiersch wire operation is totally ineffective. Some years ago Caldwell (1963). described his technique of implanting electrodes into the sphincters, and it was hoped that this physiological approach would be the answer to many pelvic floor problems. Hopkinson & Lightwood (1966) described the external plug stimulators, and were enthusiastic about the results obtained in the treatment of prolapse. However, their experience in the treatment of anorectal incontinence itself has been most disappointing. Anterior sphincter repair, such as is performed after the method performed by the gynmecologists, gives disappointing results.
Idiopathic incontinence occurs in a group ofwomen similar to those who have rectal prolapse. When examined, the patient is usually found to have a patulous external sphincter; there is virtually no power of voluntary contraction. The puborectalis is lengthened backwards, thus abolishing the normal anorectal angle. Quite frequently, however, there is reasonable contraction in this muscle on voluntary effort; this is particularly noticeable in the younger patient. The response to coughing and other causes of increased intraabdominal pressure is the reverse of normal. Instead of these muscles contracting, they are passively stretched. An active anal reflex is seldom present. The pelvic floor is usually dropped in relation to the surrounding structures even at rest. In the normal state the anal canal is roughly situated on a line drawn between the pubis and the coccyx. In these patients it may be several centimetres below this level, even at rest. When the patient is asked to strain, as at deftecation, the pelvic floor descends even further, to as much as 7 or 8 cm, the anal canal is attenuated, and at the peak of straining the anus gapes and mucosal prolapse appears. The loss of tone and stretching of the puborectalis at rest leads to the loss of the normal anorectal angulation and of the efficiency of the flap valve mechanism. This can be shown by means of defecating proctograms, but more simply by taking lateral X-rays of the patients with a bariulm-soaked swab in the rectum. Physiological testing of the anorectal mechanism in these patients reveals a low-pressure profile, which is probably due to stretching of the internal sphincter. The pressures developed on voluntary contraction vary greatly, but are usually much less than normal. Electromyography shows some tonic reflex activity to be present, mostly in the puborectalis muscle but diminished in the external sphincter. This is inhibited much more readily than normally by defaecation straining or by distension of the rectum with a balloon. All these features are seen in the patient whose rectal prolapse has been cured by rectopexy, but who is still incontinent. In idiopathic incontinence, however, it is not possible to blame prolapse and its stretching effect for the muscle weakness.
Treatment by Postanal Repair of the Pelvic Floor Muscles Seventy-five patients with incontinence have been treated over the past fifteen years. The cases fell into two major groups, those who were in all other respects normal and those who had an associated massive procidentia. Patients with primary idiopathic incontinence without major prolapse were treated with an operation to reconstruct the pelvic floor, as a primary procedure. In those patients with a large rectal prolapse this was first treated by some form of rectopexy, usually the Ivalon sponge implant, coupled with lateral ligament suspension to the sacrum, which raises the whole pelvic floor. This not only fixes the rectum so that it does not prolapse and stretch the anal sphincters, but fixes the pelvic floor at a higher level. After this type of operation about half the patients who were incontinent prior to rectal fixation achieved reasonable though not perfect control. It is the remainder who continue to be incontinent who require pelvic floor reconstruction in addition. Therefore, the two groups consist of those who have incontinence but no prolapse and those who present with prolapse but remain incontinent following rectopexy, and are treated very
similarly. Operative technique: Any operation designed to relieve this condition must take into account the fact that the muscles are already partially degenerate. The aim is to make the residual function maximally effective. An essential part of any procedure must be the reconstruction of the anorectal angulation, with the restoration of the flap valve mechanism. This objective can be obtained by reconstructing the pelvic floor muscles, which is done by approaching them
26
686 Proc. roy. Soc. Med. Volume 68 November 1975
Fig 6 The incision is made about S cm behind the anal canal. Following repair it will be drawn nearer to the anal orifice. (Reproducedfrom Parks 1971b by kindpermission)
behind the rectum and anal canal. The access is one of great anatomical interest, as they must be approached from their visceral aspect. The approach is essential for two reasons: only in this manner can the sutures be placed so that the muscle ring is narrowed; and an approach from the opposite surface would interfere with both nerve and blood supply. To gain access to the visceral surface of the muscles the viscus must first be lifted off them and displaced forwards. This is made possible by the fact that the plane between the viscus and the muscles of the pelvic floor is one of embryonic fusion. It can be approached through an incision made about 4-5 cm behind the anal canal (Fig 6). The skin is reflected forwards and the plane between the internal and external sphincters identified. The internal sphincter is then swept off the external sphincters posteriorly and laterally, so that the inner surface of the sphincter muscles is exposed (Fig 7). If the plane is pursued further upwards the puborectalis is reached; the anorectal viscus is stripped off this muscle with blunt dissection as far forwards as possible, and once its upper limit is reached the pelvic cavity is entered. Waldeyer's fascia is divided and the pararectal fat is reached. This is swept off the levator ani muscles without difficulty, as far laterally and upwards as possible. In this way the visceral surface of about twothirds of the sphincter muscles and puborectalis is identified and almost all the surface of the levator ani muscles can be seen. The cavity is large and deep. Sutures can now be placed from one side of the pelvis to the other, incorporating the levator ani muscles on each side. These muscles will not meet and the sutures form only a lattice. However, a layer of sutures below this in the pubococcygeus will allow this muscle to be approximated, so that the anorectal angle is reconstituted (Fig 8). These sutures (floss nylon is
the material which has been almost routinely used) are loosely tied and, indeed, a gap is usually left between the muscles to make sure that necrosis does not occur. At a lower level still, the two limbs of the puborectalis are lightly opposed using the same suture material and once again this recreates the normal anorectal angle. It also greatly narrows the arc of action of the puborectalis, making it mechanically much more efficient. Similar stitches are placed in the external sphincters below the puborectalis to narrow the -. arc of these muscles as well. At the end of the operation there is a lattice across the pelvis joining the levator muscles, the two limbs of both pubococcygeus and puborectalis muscles are approximated to recreate the anorectal angle, and the sphincter muscles are tightened. Indeed, if a successful result is to be obtained, the whole anal canal must feel somewhat stenosed at the end of the operation. A Redivac drain is placed in the pelvis to prevent a hiematoma from forming. Postoperative care: Many of these patients have had atonic rectal function for years and have obtained evacuation only by abdominal straining.
Fig 7 Diagrams to show the stages ofdissection. The intersphincteric plane is pursued upwards,finally exposing the cavity between the pararectalfat and the levator ani muscles. (Reproducedfrom Parks 1971b by kindpermission)
27
Section ofProctology
687
the other 52, prolapse was the main symptom in 20, incontinence was the main symptom in 25, and in the remaining 7 incontinence and prolapse featured equally. Of the 23 patients with incontinence, 18 had had no previous rectopexy; 5 had, however, had rectopexy procedures performed elsewhere. Naturally, rectopexy has no beneficial effect in patients with idiopathic incontinence. Of the 52 with both prolapse and incontinence, 9 had a rectopexy performed first, followed by a postanal repair of their pelvic floor muscles. Forty-three had no rectopexy. These observations were Fig 8 To show the manner in which the sutures are extended over a period of fifteen years, and it is placed between the limbs of the muscles. The most likely that at the present time a rectopexy would important effect is to reconstruct the anorectal be performed first in a somewhat higher proporangulation. (ReproducedfromParks 1971b tion of cases. In view of the experimental work of by kindpermission) Dukes & Mitchley (1962) in which they showed Indeed, this may have been why they developed that Ivalon embedded in the tissues could induce the condition in the first instance. The repair acts a sarcomatous reaction, it was considered as an obstruction to defecation, and were they to undesirable to embed this substance in patients strain in the immediate postoperative period it is under the age of 40. In this group, even though very likely that it would give way, largely by prolapse was a major symptom, a muscle repair tearing the stitches from the muscles. This can be was usually performed in the first instance. avoided by two methods: either a temporary Another reason for avoiding a pelvic operation in colostomy can be performed (which is unpopular a young woman is to lessen the likelihood of with patients) or diarrhoea can be induced, so pelvic inflammation with secondary occlusion of that no straining is required to evacuate the the fallopian tubes. There were 68 women in the series, nearly 90 % rectum. The latter method is usually adopted; to achieve this, magnesium sulphate is given both of the total. This female preponderance could be before the operation and for twelve days after- due either to a basic difference in pelvic anatomy wards. The diarrhoea is unpleasant but is effective compared with the male, or to damage done to the sphincter mechanism during childbirth. Of in preventing breakdown of the repair. It is essential for the patient to realize that the the 68 females, 15 were nulliparous and 49 had operation is only part of the treatment. Because borne children; in 4 the parity is unknown and in most cases there has been such gross atrophy of the information cannot now be obtained. The the sphincters, the muscles are liable to be incidence of nearly 22% of nullipara does not stretched even after the most effective repair. If suggest that childbirth injury is a major factor. The age incidence of those treated is seen in patients continue to strain at deftecation, gradually the pelvic floor weakens and their symptoms Fig 9. The condition is commonest in the sixth recur. It is absolutely essential therefore that they and seventh decades, and is relatively uncommon do not strain, which is difficult for a group of under the age of 50, although 13 patients were people who have persistently done just this for operated on before this age. The fall in numbers many years. In order to stimulate rectal con- in the eighth decade is largely due to case selectraction they are taught to use a glycerin sup- tion. Initial results in this age group were not good pository routinely each morning to ensure that W Female. No.=68 of evacuation takes place by the force of rectal wall Number patients. vis a tergo rather than by abdominal straining. ,innMale. No.= 7 They are also encouraged to practise sphincter JV r exercises which may help in the recovery of sphincter tone and prevent further muscle 201 weakening. Results Before going into details of the results, it is interesting to consider some of the statistics
21
681
Section of Proctology President Alan G Parks Mch
Meeting 27 November 1974
President's Address Anorectal incontinence
Anatomy and Physiology The anorectal region is composite in its embryological origin; it consists of the termination of the alimentary viscus, surrounded by the external sphincters which are of somatic origin. In Fig 1 an attempt is made to show how the visceral and somatic components are integrated. These may each be regarded as two tubes, one of which surrounds the other. The inner tube, being visceral, consists of mucosa, submucosa, circular and longitudinal muscle; it is innervated by the autonomic nervous system and is therefore not subject to voluntary control. The outer tube, composed of skeletal muscle, has the shape of a funnel, the upper part of which (the levator ani muscles) closes off the pelvic hiatus. In this way a complete pelvic -muscular diaphragm is formed, which counteracts the force of intra-abdominal pressure. The external sphincters play a major role in establishing normal continence. The dual origin of the anorectal mechanism makes this highly specialized region complicated from both the anatomical and physiological points of view.
by Alan G Parks Mch (The London Hospital, Turner Street, London El, and St Mark's Hospital, City Road, London ECI) The plight of a patient with frank fiecal incontinence is a very unhappy one indeed. There is the obvious association with uncleanliness and the feeling of being a social outcast. Suchaperson will not meet people, will not leave the house, or be able to do any shopping. If the situation is known to the family the patient may well be rejected as a result, especially in old age. It is indeed a very grave social problem, particularly with the elderly, and anything that will improve it is highly desirable. The frequency of the problem is greater than is generally realized, because patients will not discuss it and will not even tell their nearest relatives or their medical advisers. They manage to cope for some years by wearing a great deal of padding, but finally even this is of no avail.
~~~~Rectum E
>
S "
Longitudinal Muscle of Rectum
Internal Sphincter Longitudinal Layer of Anal Canal
Genito-Urinary Viscus
Fig 1 The anorectal mechanism isformedfrom two components, one visceral and the other somatic. The visceralpart comprises the termination ofthe hindgut and includes the internal sphincter and longitudinal muscles. It is surrounded by the skeletal muscle or somatic component, which is made up ofthe external sphincter muscles and the levator ani muscles. (Reproducedfrom Parks 1971a by kindpermission)
682 Proc. roy. Soc. Med. Volume 68 November 1975
22
lower border of which usually reaches the anal margin, and it appears to be merely a thickened extension of the muscle of the lower rectum. Physiologically, however, it behaves entirely differently from circular muscle elsewhere. It exists in a continuously tonic state, because of which it is almost certainly responsible for maintaining closure of the resting anal canal. Distension of the rectum or lower colon will cause immediate relaxation of the muscle. This occurs even if an anastomosis is interposed between the stimulated colon and the sphincter. There is no doubt that at times a strong tonic internal sphincter can maintain continence, even with total external sphincter paralysis. In some elderly people in whom the external sphincters are weak, Fig 2 This diagrammatic coronal section through the the internal sphincter may be the main factor at pelvicfloor again emphasizes its two-component and if this is stretched (as in the treatment work, constitution. There is aplane ofcleavage, the of fissure) incontinence can occur. intersphincteric plane, between the viscus and the The external sphincter may be divided anatosurrounding external sphincter mass mically into several parts. From the surgeon's The physiological mechanism of the pelvic point of view, however, the muscle bundles form a floor is designed to accomplish two tasks: first to continuous sheet and there are no obviously convert a potential perineal colostomy into an separate components except for the lowest fibres. automatically functioning sphincter, and second As the muscle mass is traced upwards, the puboto resist the force of intra-abdominal pressure, rectalis component is reached. This is a strong which if unopposed, would inevitably produce a bundle of fibres that almost completes a circle by perineal hernia. The linkage of these two tasks is running from one half of the arch of the pubic a complex one; at times it breaks down, for ramus around and behind the rectum to the instance, when fiecal stress incontinence occurs in ramus on the other side. It is almost a sphincter certain pathological situations. A terminal anatomically, but it does not quite meet anteriorly; storage reservoir is provided by a capacious it encircles the terminal parts of all the pelvic rectum; a complex sphincter mechanism controls viscera, and functions as a powerful sphincter in the outflow of the reservoir. In addition, a sensory the uppermost part of the anal canal. By its mechanism is required so that an awareness of contraction it maintains the anorectal angle, which is of great importance in the maintenance of rectal filling reaches the conscious level. The visceral component of the anal canal is normal continence. The plane between the visceral component of lined in its upper part by columnar cell, mucussecreting endodermal epithelium. In the course of the anal canal and the external sphincters is an embryonic development, however, ectoderm embryonic interspace. It contains connective migrates into the lower half of the anal canal, tissue linking the two parts together, but very few which is therefore lined by stratified squamous blood vessels cross it, neither does any nerve epithelium. This type of mucosa does not secrete tissue. Its main importance is a technical one; dissection can be carried out in this plane quite mucus and is dry. If endodermal mucosa reached the lower anal canal, constant mucous leakage easily and without blood loss. The visceral would occur, causing perianal pruritus and other component can be separated from the external symptoms. The squamous mucosa is very sensitive sphincters over a wide area, and it is a most and is richly supplied with nerve filaments from useful approach to the pelvic cavity and to the the inferior heemorrhoidal nerves (Duthie & visceral surfaces of the skeletal muscles of the Gairns 1960). The rich innervation, which is pelvic floor. Above the level of the puborectalis, the origin somatic and not autonomic, has great significance of the other levator muscles passes backwards as it enables the mucosa of the lower anal canal to become an important sensory component of along the sides of the wall of the pelvis; anatothe mechanism of continence. The slightest mically they are separated by their site of origin stimulation of this mucosa causes reflex contrac- into two groups, the pubococcygeus, which is a tion of the external sphincters. strong bundle, and the iliococcygeus, which is The circular muscle of the rectum continues much the weaker component. They fan out to downwards into the anal canal as the internal form a funnel-shaped structure which closes the sphincter (Fig 2). It is a powerful muscle, the pelvic hiatus on either side of the midline. Despite
23
Fig 3 The levator ani musclesform a cradle in which the lower rectum is contained. Any pressure or volume change within the rectum is therefore transmitted to the muscles
the various labels given to the different portions of the pelvic floor muscles it should be stressed that they are essentially an anatomical and physiological unit. The nerve supply comes via branches of the pudendal nerve, which courses along the undersurface of the muscles and sends branches into them, finally reaching the external sphincter. No nerve supply of any significance enters this muscle mass from the pelvic aspect; this fact has surgical significance, to be discussed later. The levator muscles form a bed in which the lower rectum lies (Fig 3). About half the rectum is thus encircled, and any change in the rectal size will immediately exert pressure on the muscle surrounding it. Muscles which are actuated only voluntarily would be useless for the task of maintaining continence, as a person's attention would constantly have to be given to them; an automatic mechanism is essential. To achieve this the pelvic floor muscles are endowed with a special type of physiological activity. They are activated by a reflex mechanism and are constantly in a state of contraction. This is in marked contrast to other skeletal muscles, most of which are inactive at rest (Fig 4 A, B). There is a reflex arc made up of stretch receptors in the pelvic floor muscles themselves; an afferent neurone passes to the cauda equina and an efferent motor neurone in turn activates the muscle. Several workers have demonstrated the presence of muscle spindles in both the levator ani muscles and the anal sphincters. This reflex ensures not only that the muscles are constantly in action, but also that their activity increases with a rise in intra-abdominal pressure.
Section ofProctology
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Thus when a person coughs, walks, laughs and so forth, the change in tension induced in the stretch receptors reflexly activates nerve fibres supplying the levator ani and sphincter muscles. In this way, every increase in abdominal pressure that tends to produce pelvic herniation is counteracted by an equal and opposite force. There is an interesting linkage between rectal distension and activity in the external anal sphincters. Distension of the rectal ampulla with a balloon containing, say, 50 ml of fluid will generally cause an excitation of the pelvic floor muscles with an increase in the basal tone. The mechanism of this linkage is of great interest and importance. It is known that the effect ceases above about 8 cm from the anal margin. It has previously been postulated that there are receptors in the wall of the rectum which act on the centres of the cauda equina to increase the activity in the motor neurones supplying the pelvic floor (Parks, et al. 1962). It was shown that this reflex did not depend on the presence of the rectal mucosa, because in patients who had had total excision of the rectal mucosa (for instance, for diffuse villous tumour of the rectum) the response was nevertheless present. After anterior resection, however, it was found that this response was present only below the anastomosis, not above it. This was regarded as strong evidence that receptors existed in the rectal wall itself. In the last three years, however, very low anastomoses have been performed, so that the colon is brought down to the upper anal canal. In these cases distension of the colon above the anal canal does give rise to the normal response in the external
Fig 4 Electromyographic recordings to show, A, that the extensor muscles of the forearm are totally inactive at rest, but develop intense electrical activity as the result ofsynergistic contraction (between T and R), whereas, B, the pelvicfloor sphincters have a constant activity
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extensive pelvic fibrosis due to infection, the sensation is normal and the patient is aware when the colon needs to be evacuated. The anal valve mechanism: It has always been supposed that the anal sphincters established continence purely by their squeeze effect; indeed, this may well be the case when voluntary contraction is called into play, but the maximal length of time for which this can be maintained is not much more than one to two minutes. Some years ago it was suggested (Parks et al. 1966) that there was a flap valve mechanism at the anorectal junction which depended on the rightangle between the axes of the lower rectum and the anal canal. Because of this, the mucosa of the lowest part of the anterior rectal wall lies across the upper end of the anal canal, which is kept closed by muscular action. This small segment of Fig 5 The valve mechanism at the anorectaljunction. anterior rectal wall is driven into the closed end Due to the angulation of the rectum with the anal of the canal by intra-abdominal pressure (Fig 5). canal, the lower part ofthe rectal wallforms a valve Every increase in intra-abdominal pressure will which occludes the closed upper anal canal. force the anterior rectal wall on to the canal and (Reproducedfrom Parks 1971a by kindpernussion) occlude the lumen; the greater the abdominal sphincter. It is therefore necessary to abandon the force, the more secure the occlusive effect. In order that defecation may take place, the view that the receptors for this reflex lie in the rectal ampulla; they are almost certainly situated valve mechanism must be unlocked. Intrain the levator ani muscles which, as mentioned abdominal pressure cannot ordinarily do this; a above, wrap themselves around the lower part of rise in intrarectal pressure must occur. Fecal matter subjected to intraluminal pressure will the rectum. Inhibition of sphincter tone also occurs during automatically lift the anterior rectal wall off the micturition and straining on defiecation. The upper anal canal. Once this has occurred, either latter is probably part of the normal mechanism intrarectal or extrarectal pressure will tend to of deftecation, as it allows the pelvic floor to drop expel the contents through the anal canal; only somewhat and causes complete sphincter relaxa- sphincter contraction can now prevent it. To summarize the present state of knowledge tion. However, if excessive defecation straining occurs in a constipated person, the pelvic floor is regarding the reflex mechanism of the pelvic forced downwards at the same time that all the floor, the afferent limb is derived almost entirely muscles are relaxed. They are therefore likely to from the skeletal muscles and from the squamous be passively stretched. Though recovery is almost anal mucosa. The same afferent end-organs certainly complete after a temporary episode of probably cause excitation or relaxation according this nature, if the habit persists for years, the to their frequency of response. The afferent repelvic floor may gradually descend, the pubo ceptors in the muscles are spindles; these have rectalis becomes stretched and the sphincters been demonstrated by several workers (Winkler 1958, Walls 1959). In the anal mucosa there are weakened. It is always difficult to discuss rectal sensation: numerous specialized sensory receptors; as far as like pain, it is impossible to define, and the feeling is known, there are no receptors in the rectum cannot be readily communicated from one itself which affect the skeletal muscle activity. person to another. There is no doubt, however, that in the normal person a full rectum is appre- Causes ofIncontinence ciated by a sense of pelvic floor discomfort which Traumatic muscle damage: The results of treatment is often associated with a sense of urgency. This of traumatic muscle section have been reported sensation can be very readily produced by elsewhere (Parks & McPartlin 1971) and will not distending the lower rectum with a balloon and, be discussed further in this paper. as discussed above, it is probably caused by filling of the rectum affecting the levator ani muscles Rectal prolapse: Porter, in his several articles on surrounding it. This is very important from the this subject (e.g. Porter 1962), has shown that the point of view of function after low anterior majority of patients with this condition have a resection. Provided that there has been no long history of defecation straining, and that two-
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Section ofProctology
thirds are incontinent before the prolapse is treated surgically. In those patients who do improve following rectopexy, the tone of the anal sphincter is also objectively improved. Nevertheless, one-third remain incontinent following rectopexy and their situation is then very similar to that of the next group to be discussed, those suffering from idiopathic incontinence without prolapse, both physiologically and from the point of view of treatment.
There must be some primary defect in the neuromuscular anorectal mechanism to account for it. Many forms of treatment for idiopathic incontinence have been tried in the past. Faradism has given disappointing results. The Thiersch wire operation is totally ineffective. Some years ago Caldwell (1963). described his technique of implanting electrodes into the sphincters, and it was hoped that this physiological approach would be the answer to many pelvic floor problems. Hopkinson & Lightwood (1966) described the external plug stimulators, and were enthusiastic about the results obtained in the treatment of prolapse. However, their experience in the treatment of anorectal incontinence itself has been most disappointing. Anterior sphincter repair, such as is performed after the method performed by the gynmecologists, gives disappointing results.
Idiopathic incontinence occurs in a group ofwomen similar to those who have rectal prolapse. When examined, the patient is usually found to have a patulous external sphincter; there is virtually no power of voluntary contraction. The puborectalis is lengthened backwards, thus abolishing the normal anorectal angle. Quite frequently, however, there is reasonable contraction in this muscle on voluntary effort; this is particularly noticeable in the younger patient. The response to coughing and other causes of increased intraabdominal pressure is the reverse of normal. Instead of these muscles contracting, they are passively stretched. An active anal reflex is seldom present. The pelvic floor is usually dropped in relation to the surrounding structures even at rest. In the normal state the anal canal is roughly situated on a line drawn between the pubis and the coccyx. In these patients it may be several centimetres below this level, even at rest. When the patient is asked to strain, as at deftecation, the pelvic floor descends even further, to as much as 7 or 8 cm, the anal canal is attenuated, and at the peak of straining the anus gapes and mucosal prolapse appears. The loss of tone and stretching of the puborectalis at rest leads to the loss of the normal anorectal angulation and of the efficiency of the flap valve mechanism. This can be shown by means of defecating proctograms, but more simply by taking lateral X-rays of the patients with a bariulm-soaked swab in the rectum. Physiological testing of the anorectal mechanism in these patients reveals a low-pressure profile, which is probably due to stretching of the internal sphincter. The pressures developed on voluntary contraction vary greatly, but are usually much less than normal. Electromyography shows some tonic reflex activity to be present, mostly in the puborectalis muscle but diminished in the external sphincter. This is inhibited much more readily than normally by defaecation straining or by distension of the rectum with a balloon. All these features are seen in the patient whose rectal prolapse has been cured by rectopexy, but who is still incontinent. In idiopathic incontinence, however, it is not possible to blame prolapse and its stretching effect for the muscle weakness.
Treatment by Postanal Repair of the Pelvic Floor Muscles Seventy-five patients with incontinence have been treated over the past fifteen years. The cases fell into two major groups, those who were in all other respects normal and those who had an associated massive procidentia. Patients with primary idiopathic incontinence without major prolapse were treated with an operation to reconstruct the pelvic floor, as a primary procedure. In those patients with a large rectal prolapse this was first treated by some form of rectopexy, usually the Ivalon sponge implant, coupled with lateral ligament suspension to the sacrum, which raises the whole pelvic floor. This not only fixes the rectum so that it does not prolapse and stretch the anal sphincters, but fixes the pelvic floor at a higher level. After this type of operation about half the patients who were incontinent prior to rectal fixation achieved reasonable though not perfect control. It is the remainder who continue to be incontinent who require pelvic floor reconstruction in addition. Therefore, the two groups consist of those who have incontinence but no prolapse and those who present with prolapse but remain incontinent following rectopexy, and are treated very
similarly. Operative technique: Any operation designed to relieve this condition must take into account the fact that the muscles are already partially degenerate. The aim is to make the residual function maximally effective. An essential part of any procedure must be the reconstruction of the anorectal angulation, with the restoration of the flap valve mechanism. This objective can be obtained by reconstructing the pelvic floor muscles, which is done by approaching them
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Fig 6 The incision is made about S cm behind the anal canal. Following repair it will be drawn nearer to the anal orifice. (Reproducedfrom Parks 1971b by kindpermission)
behind the rectum and anal canal. The access is one of great anatomical interest, as they must be approached from their visceral aspect. The approach is essential for two reasons: only in this manner can the sutures be placed so that the muscle ring is narrowed; and an approach from the opposite surface would interfere with both nerve and blood supply. To gain access to the visceral surface of the muscles the viscus must first be lifted off them and displaced forwards. This is made possible by the fact that the plane between the viscus and the muscles of the pelvic floor is one of embryonic fusion. It can be approached through an incision made about 4-5 cm behind the anal canal (Fig 6). The skin is reflected forwards and the plane between the internal and external sphincters identified. The internal sphincter is then swept off the external sphincters posteriorly and laterally, so that the inner surface of the sphincter muscles is exposed (Fig 7). If the plane is pursued further upwards the puborectalis is reached; the anorectal viscus is stripped off this muscle with blunt dissection as far forwards as possible, and once its upper limit is reached the pelvic cavity is entered. Waldeyer's fascia is divided and the pararectal fat is reached. This is swept off the levator ani muscles without difficulty, as far laterally and upwards as possible. In this way the visceral surface of about twothirds of the sphincter muscles and puborectalis is identified and almost all the surface of the levator ani muscles can be seen. The cavity is large and deep. Sutures can now be placed from one side of the pelvis to the other, incorporating the levator ani muscles on each side. These muscles will not meet and the sutures form only a lattice. However, a layer of sutures below this in the pubococcygeus will allow this muscle to be approximated, so that the anorectal angle is reconstituted (Fig 8). These sutures (floss nylon is
the material which has been almost routinely used) are loosely tied and, indeed, a gap is usually left between the muscles to make sure that necrosis does not occur. At a lower level still, the two limbs of the puborectalis are lightly opposed using the same suture material and once again this recreates the normal anorectal angle. It also greatly narrows the arc of action of the puborectalis, making it mechanically much more efficient. Similar stitches are placed in the external sphincters below the puborectalis to narrow the -. arc of these muscles as well. At the end of the operation there is a lattice across the pelvis joining the levator muscles, the two limbs of both pubococcygeus and puborectalis muscles are approximated to recreate the anorectal angle, and the sphincter muscles are tightened. Indeed, if a successful result is to be obtained, the whole anal canal must feel somewhat stenosed at the end of the operation. A Redivac drain is placed in the pelvis to prevent a hiematoma from forming. Postoperative care: Many of these patients have had atonic rectal function for years and have obtained evacuation only by abdominal straining.
Fig 7 Diagrams to show the stages ofdissection. The intersphincteric plane is pursued upwards,finally exposing the cavity between the pararectalfat and the levator ani muscles. (Reproducedfrom Parks 1971b by kindpermission)
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the other 52, prolapse was the main symptom in 20, incontinence was the main symptom in 25, and in the remaining 7 incontinence and prolapse featured equally. Of the 23 patients with incontinence, 18 had had no previous rectopexy; 5 had, however, had rectopexy procedures performed elsewhere. Naturally, rectopexy has no beneficial effect in patients with idiopathic incontinence. Of the 52 with both prolapse and incontinence, 9 had a rectopexy performed first, followed by a postanal repair of their pelvic floor muscles. Forty-three had no rectopexy. These observations were Fig 8 To show the manner in which the sutures are extended over a period of fifteen years, and it is placed between the limbs of the muscles. The most likely that at the present time a rectopexy would important effect is to reconstruct the anorectal be performed first in a somewhat higher proporangulation. (ReproducedfromParks 1971b tion of cases. In view of the experimental work of by kindpermission) Dukes & Mitchley (1962) in which they showed Indeed, this may have been why they developed that Ivalon embedded in the tissues could induce the condition in the first instance. The repair acts a sarcomatous reaction, it was considered as an obstruction to defecation, and were they to undesirable to embed this substance in patients strain in the immediate postoperative period it is under the age of 40. In this group, even though very likely that it would give way, largely by prolapse was a major symptom, a muscle repair tearing the stitches from the muscles. This can be was usually performed in the first instance. avoided by two methods: either a temporary Another reason for avoiding a pelvic operation in colostomy can be performed (which is unpopular a young woman is to lessen the likelihood of with patients) or diarrhoea can be induced, so pelvic inflammation with secondary occlusion of that no straining is required to evacuate the the fallopian tubes. There were 68 women in the series, nearly 90 % rectum. The latter method is usually adopted; to achieve this, magnesium sulphate is given both of the total. This female preponderance could be before the operation and for twelve days after- due either to a basic difference in pelvic anatomy wards. The diarrhoea is unpleasant but is effective compared with the male, or to damage done to the sphincter mechanism during childbirth. Of in preventing breakdown of the repair. It is essential for the patient to realize that the the 68 females, 15 were nulliparous and 49 had operation is only part of the treatment. Because borne children; in 4 the parity is unknown and in most cases there has been such gross atrophy of the information cannot now be obtained. The the sphincters, the muscles are liable to be incidence of nearly 22% of nullipara does not stretched even after the most effective repair. If suggest that childbirth injury is a major factor. The age incidence of those treated is seen in patients continue to strain at deftecation, gradually the pelvic floor weakens and their symptoms Fig 9. The condition is commonest in the sixth recur. It is absolutely essential therefore that they and seventh decades, and is relatively uncommon do not strain, which is difficult for a group of under the age of 50, although 13 patients were people who have persistently done just this for operated on before this age. The fall in numbers many years. In order to stimulate rectal con- in the eighth decade is largely due to case selectraction they are taught to use a glycerin sup- tion. Initial results in this age group were not good pository routinely each morning to ensure that W Female. No.=68 of evacuation takes place by the force of rectal wall Number patients. vis a tergo rather than by abdominal straining. ,innMale. No.= 7 They are also encouraged to practise sphincter JV r exercises which may help in the recovery of sphincter tone and prevent further muscle 201 weakening. Results Before going into details of the results, it is interesting to consider some of the statistics
