Br. J. Surg. Vol. 62 (1975) 542-552

The nature of haemorrhoids* W . H. F . T H O M S O N t SUMMARY

An anatomicai and ciinicai study aimed at uncovering factors likely to be helpful in understanding the true nature of haemorrhoids is described. The main finding was of specialized ‘cushions’ of submucosal tissue lining the anal canal; it is argued that piles are merely the result of their displacement. THEtheory that haemorrhoids result from varicosity of the anal submucosal veins, although currently orthodox, is not the only one available nor has it always been the most popular. In the past century, in fact, most European authorities considered piles to be caused by some sort of vascular tissue hyperplasia -a concept which recent work in Germany seems to support. Another theory suggests that piles are caused simply by a downward displacement of the anal canal lining. The three theories will now be reviewed.

The varicose vein theory Dating from the time of Galen and Hippocrates (Parks, 1955), this theory probably stems from the observation of discrete dilatations on the course of the veins within the tissues of a haemorrhoid-John Hunter noticed them in a specimen that he dissected and clearly thought them to be the cause of haemorrhoids (Hunterian Museum (1 848) Descriptive Catnlogue). The dilatations being thought of as the basic pathological change, various explanations were put forward to account for their development. There are two main groups: (1) explanations incriminating a localized increase in venous pressure, and (2) explanations incriminating a localized weakness in the vein wall. The various mechanisms suggested as bringing about an increase in venous pressure are based on certain anatomical observations; the absence of valves in the portal vein and its tributaries, and the degree and site of the communications between the portal and systemic circulations in the anal canal. Morgagni (1 749) introduced the idea that localization of the ‘varices’ to the anus might be attributable to the upright posture of man (the effect of the hydrostatic pressure resulting from an uninterrupted column of blood), and agreed with Boerhaave that the increased intra-abdominal pressure of straining would be transmitted to the anal veins. Verneuil(1855b), after injecting and dissecting the superior rectal vein and failing to find comniunications between it and the systemic circulation, suggested that the dilatations might be the result of obstruction to the venous return at the point where he had found the veins to pass through unprotected muscular ‘button-holes’ in the rectal wall (he thought the success of forcible 542

dilatation of the anus-which he had introduced empirically in the treatment of piles-to be due to stretching of the ‘button-holes’ (Allingham and Allingham, 1896). Duret (1877) made similar dissections but discovered communications between the two systems traversing the anal sphincter. He therefore thought the fault lay in venous obstruction due to anal sphincter spasm and suggested a mechanism whereby the venous return upwards would also be cut off during defaecation. Because none of the ideas of Morgagni, Verneuil or Duret seemed to explain the curious localization of the ‘varices’ to the lower half of the anal canal, Parks ( 1 956) and later Graham-Stewart (1 963) put forward alternative theories (although based on Duret’s description of the anatomy) which seemed more adequately to fit the facts. However, free communications between the portal and systemic circulations in the anal canal have been demonstrated by Cruveilheir (1867), Konstantinowitch (1872), QuCnu (1892) and Tuttle (1906) and so the concept that a localized increase in venous pressure is to blame in haemorrhoids is based on uncertain anatomical evidence. Quenu, recognizing the lack of an anatomical mechanism to mediate a local increase in venous pressure, suggested that the fault lay in a weakness in the vein wall. He suggested that the venous dilatations, which he called ‘haemorrhoids in miniature’ (Quknu and Hartmann, 1895; Fig. I), might be a manifestation of vein wall destruction brought about by recurrent infections resulting from repeated minor trauma at defaecation. He recognized, however, that there was little histological evidence to back up his ideas and his theory was never generally accepted. Recently, in fact, Jackson and Robertson (1965) reported that they had found no evidence of past or current infection in the haemorrhoidectomy specimens they had examined over the course of 2 years. From this brief history the varicose vein theory can be seen to depend upon the observation of venous dilatations in the tissues of piles. However, Sappey (1874), Duret (1877) and Waldeyer (1899) have all reported finding dilatations on the course of the anal canal veins in children, suggesting that they are normal structures.

The vascular hyperplasia theory Popular in the nineteenth century-Malgaigne (1837), Velpeau (1826), Bourgery (1840) and Cruveilhier ( I 852) considering piles to result from a sort of erectile

* The subject of a thesis accepted by London University for a Master of Surgery degree, 1974. t Southampton General Hospital. Present address: Gloucester Royal Hospital.

The nature of haemorrhoids tissue metaplasia, and Virchow ( 1 863) and Allingham ( I 973) considering them to be haemangiomatous in nature-this theory probably arose out of the observed similarity between the tissues of a pile and cavernous tissue (Hunter, 1728-1793). The special nature of the anal submucosa, which Bourgery (1840) likened t o an ‘erectile w e b and which Treitz (1853) noticed t o be extraordinarily thick, was considered by Stieve (1928) to function as part of the anal continence mechanism by contributing t o anal closure. Staubesand et al. (1963) demonstrated arteriovenous communications in the anal submucosa which seemed to them to indicate that the anal submucosa (which they also likened to cavernous tissue and called the ‘corpus cavernosum recti’) might have erectile properties; if so it would enhance, they believed, its capacity to fulfil its supposed function. Their observations stimulated them and Stelzner (1963) to suggest that piles might result from hyperplasia of the ‘corpus cavernosum recti’. They cited in support the bright red colour of the bleeding (explicable, if coming from the venous spaces, on the basis of the existence of arteriovenous communications) and the fact that the bleeding of piles is said to be their earliest manifestation.

The sliding anal lining theory Gass and Adams (I 950) considered piles to resui t from degeneration of supportive tissue in the anal canal because of their observation, in 200 haemorrhoidectomy specimens, of fragmentation of connective tissue, and their belief that haemorrhoids were associated with a lax anus. Hughes (1957) and Patey ( I 972) supported the idea because it fitted the appearance of piles. Of relevance is the existence in the anal submucosa of a substantial layer of smooth muscle. It was first described by Treitz (1853), who noted that it arose partly from the internal sphincter and parlly, by passing through the internal sphincter, from the conjoined longitudinal muscle. He described it as passing downwards in the anal submucosa to form a supporting scaffold around the veins of the haemorrhoidal venous plexus and as making a significant contribution to the bulk of the columns of Morgagni. He considered it to function in preventing prolapse of the bulky tissues of the anal lining. Kohlrausch (1854), in describing it, expressed a similar view and called it the ‘sustentator tunicae mucosae’. Ellis also discovered it in 1854 (Ellis and Ford, 1867) and, ignorant of the other two reports, called it the ‘corrugator cutis ani’. Beraud (1858) next reported it, and later still, Roux (1881). Finally, it was described by Fine and Lawes (1940) who called it the ‘muscularis submucosi ani’. For the sake of brevity and in recognition of his original discovery it will be called here ‘Treitz’s muscle’. Despite its repeated documentation it has yet to find a proper place in modern textbooks of anatomy. The following investigation was undertaken in order to examine the premisses upon which the three hypotheses are based.

Fig. 1. Diagram from QuCnu and Hartmann’s (1895) Chirurgie drr Recrirtn, showing the haernorrhoidal venous plexus after injection and dissection. The appearance of the venous dilatations, which they thought to be pathological, seems to have given rise to the term ‘bunches of grapes’ in connection with haemorrhoids.

Materials and methods The study was partly anatomical and partly clinical. The anatomical study Ninety-five cadaveric anorectal specimens (obtained by pelvic exenteration en bloc with the anal canal from 10 infants, 3 adolescents and 82 adults) were prepared and dissected. Proctoscopy, with photography to provide a record, was carried out in 42 patients without haemorrhoids. Demonstration of the arterial system: Fifty adult specimens were used. Each was prepared by injecting the superior rectal artery with latex and slitting the specimen open in the anterior midline. The entire extrarectal and submucosal course of the superior, middle and inferior rectal arteries (the parts incorporated in the specimen) was then dissected and a diagram made from each dissection. Demonstrotion of the venous system: Fifty adult, 3 adolescent and 10 infant specimens were used. In 25 of the adult specimens the superior rectal vein was injected with a barium sulphate suspension and the specimen was slit open anteriorly and X-rayed. In the other 25 latex was injected and the venous system was dissected. The 10 infant and 3 adolescent specimens were prepared in a different way. First, the superior rectal vein was cannulated and injected retrogradely with diluted ammoniated latex (Tompsett, 1970)Fbefore removal of the specimen in order to facilitate cannulation (manipulation during removal usually empties the vein, which in infants then becomes invisible). Next the specimen was removed and the anorectum was slit open anteriorly. The anal canal lining, in 543

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Fig. 2. Diagrams of the posterior aspect of dissected anorectal specimens showing five different patterns of arterial supply. The extrarectal course is represented by a continuous line and the submucosal by a dotted one. The middle rectal arteries can be seen joining the specimens anterolaterally above the levatores ani, and the inferior rectal vessels below the muscle, mainly posteromedially.

continuity with a cuff of perianal skin, was then dissected off the internal sphincter and subcutaneous part of the external sphincter and pinned out in formalin. After fixation it was rendered translucent by Spalteholz’s technique (Culling, 1963) and studied under the dissecting microscope. Demonstration of the arteriovenous communications: An anorectal specimen removed from the corpse of a young man soon after death was prepared. Infusion with saline through cannulae in both the superior rectal artery and vein enabled all severed vessels to be detected and sealed and the vascular tree to be cleared of blood. On completion (when perfusion of the superior rectal artery resulted in an almost clear flow from the vein) simultaneous infusion of the artery and vein was carried out using diluted ammoniated and filtered latex at constant pressure (red latex at 200 mm Hg and blue latex at 80 mm Hg respectively). The anal canal lining was then removed, rendered 544

translucent as before and studied under the dissecting microscope. Demonstration of Treitz’s muscle : Treitz’s muscle was demonstrated both macroscopically and microscopically. It was seen with the naked eye on raising the flap of anal lining as described above. Thirty-five specimens, slit open anteriorly, were dissected in the following manner; the perianal skin was dissected off the ischiorectal fat and external sphincter and, working cephalad, off the lowermost part of the internal sphincter; the muscle was then seen as a continuous layer of longitudinally running fibres on the deep surface of the flap. Further dissection showed it to arise circumferentially from the deep surface of the internal sphincter in almost discrete bundles which passed downwards into the anal submucosa and which had to be divided in order to elevate the flap. The appearance was recorded photographically. For its microscopic demonstration longitudinal and transverse sections were made of the anal canal. In order to demonstrate its relationship to the venous plexus the veins were first distended by injecting the superior rectal vein with a mixture of barium sulphate and 4 per cent gelatin. Demonstration of the anal ‘cushions’: This term, introduced for the first time, is used here to describe cushions of submucosal tissue in the anal canal. They were first observed during the proctoscopic examination of 42 consecutive patients with neither symptoms nor signs of haemorrhoids, and subsequently demonstrated in the anatomical preparations. The completely dissected flap of anal canal lining described above was merely held up to the light; discrete masses of thickened submucosa could then be clearly seen. They were demonstrated in 35 consecutive specimens-25 from adults and 10 from infants. Prior injection of the venous plexus made the cushions more obvious. Proctoscopic examination of normal controls was carried out in the hope that it might provide information to explain the regular appearance of piles in the right anterior, right posterior and left lateral positions in the anal canal (Goodsall and Miles, 1900). It became clear that the anal lumen was not a simple anteroposterior slit as usually described (Phillips and Edwards, 1965) but a basically triradiate one. The appearance of the anal lumen in 42 normal patients was recorded photographically. The clinical study Eighty consecutive patients admitted to Southampton General Hospital for the surgical treatment of their prolapsing piles were asked which of their symptoms had started first, the bleeding or the prolapse. At operation the position and appearance of the piles were recorded by colour photography. The haemorrhoidectomy specimens were studied histologically.

Results The anatomical study The arterial system: Miles (1919) wrote that the branching pattern of the superior rectal artery was constant, being characterized by a bifurcation of the

The nature of haemorrhoids

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main trunk into right and left branches with the right branch then producing anterior and posterior divisions while the left remained substantially single. He stated that it thereby determined the position of piles around the anal circumference (accounting for their regular appearance in the right anterior, right posterior and left lateral positions)-piles being said to be due to varicosity of the radicles of the superior rectal vein which, he said, followed the branches of the artery. However, Miles’s description would not have been applicable to any of the 50 specimens which the present author has dissected, despite there being a wide variety of branching patterns amongst them (Fig. 2). In 23 specimens (46 per cent) the pattern was found to conform to the orthodox description (Warwick and Williams, 1973), the main trunk birfurcatiiig to produce right and left divisions which then divided into a variable number of branches supplying the ipsilateral side of the rectum and anal canal:, in the other 27 specimens various patterns were found. In some the main trunk passed to the right, giving off branches to the left, in others it passed to the left, supplying branches to the right, and in another group there was a trifurcation of the main trunk. The trifurcation group was also not uniform since the central component behaved in a number of different ways-supplying branches to both sides of the anal canal in some, to one side only in others and in yet others not reaching the anal canal, supplying only the rectum. Furthermore, the arrangement of the branches as they pierced the wall of the rectum to pass down into the anal submucosa was found to be unrelated to the primary branching pattern of the superior rectal artery; it was not unusual, in fact, to find a large primary branch being spent entirely in the supply of the rectum, not reaching the anal submucosa at all. An average of five branches of the superior rectal artery was found actually to reach the haemorrhoidal zone (Fig. 3). However, in 35 specimens (70 per cent) substantial branches of one or both middle rectal arteries could also be traced into the anal submucosa, and in 21 specimens (42 per cent) the inferior haemorrhoidal arteries were found to make a similar contribution. 39

Fig. 4. X-ray of an opened-out anorectal specimen in which the superior rectal vein has been injected with a barium sulphate suspension. There was no evidence of piles; in other specimens where gross pile formations were present the radiographic appearance was the same.

Fig. 5. Adult anorectal specimen prepared by latex injection of the superior rectal vein, followed by Spalteholz’s procedure to render the tissues translucent; specimen slit open anteriorly.

In 5 specimens (10 per cent) a n interesting and previously undescribed vascular anomaly was encountered, the middle rectal artery usurping, in the supply of the anal canal, part (and in 1 specimen, all) of the function of the superior rectal artery. Instead of piercing the muscle wall low down anteriorly as is usual (below the attachment of the levator ani at the 545

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Fig. 6. Anorectal specimens from a full-term neonate (a) and a 3-month old infant (b). The superior rectal vein had been injected with coloured latex and the tissues cleared by Spalteholz’s technique.

Fig. 7. A projection drawing of the arteriovenous communications in the anal submucosa; arteries white, veins stippled.

anorectal junction), the middle rectal artery pierced the rectal wall anterolaterally 3-4 cm above the levatores ani-where the superior rectal artery normally traverses the muscle wall. It then ran down into the anal submucosa to supply whole segments of it in place of the superior rectal; in the case of the specimen referred to in parentheses above the entire anal submucosa was supplied by the two middle rectal arteries. I n summary the anal lining derives a rich blood supply from the superior, middle and inferior rectal arteries, whose branches reach the anal submucosa in a most varied way. The venous system-venous dilatations: Each of the 50 adult specimens exhibited discrete dilatations on the course of the veins of the anal submucosal venous plexus. A typical X-ray is illustrated in Fig. 4 and the typical appearance of a latex-injected specimen is shown in Fig. 5. The dilatations may be fusiform, saccular or serpiginous and are confined to the lower half of the anal canal. Above the pectinate line they 546

occur in greatest profusion and complexity, but a second series-fewer in number and with a tendency to be larger in size-occurs below it. In 3 specimens thrombosis (confirmed histologically) had occurred recently in a dilatation below the pectinate line; the appearance was the same as that known as ‘perianal haematoma’. Of the 10 infant specimens, venous dilatations were found in 8 (Fig. 6). The 2 specimens in which they were absent were obtained from the bodies of very small stillbirths. The venous system-portosystemic communications : Free communications both below and through the anal sphincter were demonstrated between the tributaries of the superior, middle and inferior rectal veins in all 25 specimens in which dissection was possible (the ones in which the veins had been injected with latex). They were also seen in all 25 specimens where radiography was employed (see Fig. 4), although the two-dimensional limitations of the X-rays precluded determination of their exact course. The communicating veins passing below the anal sphincter to join the subcutaneous tributaries of the inferior rectal vein were seen in all the specimens in which the anal canal lining had been removed and rendered translucent (see Figs. 5 , 6). Arteriovenous communications : In the specimen prepared for their demonstration red latex from the arterial side was seen under the dissecting microscope to have filled some of the venous dilatations by way of tiny direct arteriovenous communications. Because they wound through different planes it was not possible to demonstrate them photographically. A few dissected ones were sketched using the drawing attachment on a Wild Stereo-Zoom dissecting microscope; a drawing is illustrated in Fig. 7. Treitz’s muscle: Easily found in all 35 specimens, Treitz’s muscle was seen to emerge from the internal sphincter at different levels in almost discrete, overlapping bands (Fig. 8). The bands passed downwards into the anal submucosa to form a continuous sheet on the deep surface of the submucosa from the pectinate line downwards. Microscopy demonstrated it to arise partly from the internal sphincter itselfthe circular fibres of which seemed to curve inwards

The nature of haemorrhoids and downwards to form it-and partly from the conjoined longitudinal muscle, the contributing fibres passing between the imbricated fasciculi of the internal sphincter. It was found to be distributed in three ways: to form a network around the haemorrhoidal venous plexus, to fan out into the perianal skin and to rejoin the longitudinal muscle (either around the lower border of the internal sphincter or through its lowermost fasciculus). It was found to contain a considerable amount of elastic tissue and to be hypertrophied, sometimes markedly so, in specimens exhibiting prolapsing haemorrhoids. The anal ‘cushions’: As a result of the proctoscopic examination of patients with neither the symptoms nor signs of piles, the anal lumen was observed to form a more or less triradiate slit (Fig. 9). The stem of the ‘Y’ so formed was found invariably to approach the midline posteriorly, with its arms embracing a pad of tissue anteriorly or, more usually, in the right anterior position. The three folds thus separated three pads of tissue, the anal ‘cushions’, lying in the left lateral, right anterior and right posterior positions. Secondary folds were found to intersect the cushions to a variable degree. The anatomical dissections (Fig. 10) demonstrated the cushions to be caused by thickenings in the submucosa, and histology showed them to be composed largely of blood vessels (the venous dilatations making the main contribution), smooth muscle (Treitz’s muscle) and elastic and connective tissue. The c o h l n s of Morgagni are produced by longitudinal clefts in the anal cushions. With little doubt they represent the mechanism whereby the cushions are able to adapt to the large changes in size of the anal lumen. Their relationship to the anal cushions can only be seen properly in specimens in which the haemorrhoidal venous plexus has been filled. The clinical study Order of appearance of symptoms: The results from questioning 66 patients with prolapsing piles are displayed in Fig. 11. The majority of patients (60 per cent) claimed that prolapse had been the first symptom. Only 8 patients (12 per cent) thought that bleeding had started first, of whom one had a coexistent rectal polyp, one had anal fissure and a third gave an unreliable history, being mentally retarded. I n only 5 patients, therefore, did it seem certain that the first manifestation of piles had been bleeding. Histology of haemorrhoidectomy specimens : Twentyfive haemorrhoidectomy specimens were examined. They showed a stroma of connective tissue containing many blood vessels, and interweaving bundles of smooth muscle. Large vascular spaces were found to a greater or lesser extent in all the specimens, but apart from exhibiting evidence of recent or past thrombosis they were similar to the ones seen in the submucosa Of cadaveric specimens in which there was no evidence Of Piles. There was no sign of vascular hyperplasia.

Haemorrhoida

Fig. 8. A composite diagram of Treitz’s muscle derived from longitudinal sections of the anal canal.

Fig. 9. The proctoscopic appearance of the anal ‘cushions’ in a normal individual. The triradiate configuration of the anal lumen is well shown.

547

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Fig. 10. Twelve anorectal specimens in which the anal lining has been dissected u p and viewed with transmitted light. The arrangement of the anal cushions is similar.

548

The nature of haemorrhoids The large vascular spaces were found lo be deep in the substance of the pile, separated from the surface not only by connective tissue but by the muscularis mucosae. Many piles were noticed t o have a red granular mucosa which histology revealed to be due to a rich network of dilated capillaries in the lamina propria (between the mucosal epithelium and the muscularis mucosae). Bleeding from these capillaries was clearly seen in some sections.

Prolapse started first Bleeding started first Bleeding and prolapse started simultaneously Prolapse onlyn o bleeding

Discussion

Patient could not remember which symptom started first

The arterial system

Konstantinovitch (1 872), QuCnu (1893) and Widmer (1955) made dissections of the superior rectal artery; no other reports of personal dissections have been found in the literature. The present author’s findings concerning its course and distribution are similar t o theirs. None of them reported a n arrangement similar to that described by Miles (1919), and Miles does not disclose the source of his information. No evidence from the author’s dissections o r from those reported by others supports his contention that the branching pattern of the superior rectal artery is responsible for the position of piles around the anal circumference.

The uetious system The present study has confirmed the observations of Sappey (1874), Duret (1877) and Waldeyer (1899) that the dilatations of the veins of the haemorrhoidal venous plexus are constant and normal structures, being present from birth and being found in all adults. Quenu (1892) seems t o be the only one to have looked for them in children in vain. His failure was undoubtedly due t o his technique-he was unable to cannulate the superior rectal vein in children because of its smallness and therefore could not inject it. The findings of Cruveilhier (1867), Konstantinovitch (1872), QuCnu (1 892) and Tuttle (1906) concerning the abundance of communications between the portal and systemic circulations both below and through the anal sphincter have also been confirmed. The fact that Verneuil(1855a) was unable t o find any a t all and that Duret (1877) only found the ones passing through the sphincter is presumably attributable to technique. Arteriouenoirs communications

Direct arteriovenous communications in the anal submucosa have been demonstrated by serial section (Stelzner et al., 1962) and by radiography (Schmidt and Staubesand, 1972) and now using the latexinjected preparation described here. As suggested by Staubesand et al. (1963), the anal submucosa may have a n erectile property and the arteriovenous communications may function in the erectile mechanism. The enormous blood supply that the anal submucosa receives-greatly in excess of the conceivable metabolic requirements of its constituent cells -is further evidence for the existence of such a mechanism.

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Fig. 11. The chronological order of appearance of symptoms in 66 patients admitted for treatment of prolapsing piles.

Treitz’s muscle

As described by Treitz (1853), the haemorrhoidal

venous plexus was found to be supported by a scaffold of smooth muscle and elastic tissue which was found t o arise partly from the internal sphincter and partly from the conjoined longitudinal muscle. Both Treitz (1853) and Kohlrausch (1854) thought its function to be the support of the anal lining during defaecation. I n view of the bulkiness of the anal lining (due to the anal cushions) and the strategic arrangement of the muscle their opinion is probably correct. The anai cushions Bourgery (1839) observed the anal lining t o form a bolster, and Treitz (1853) also commented o n its thickness. Stieve (1928) noted that it shared this characteristic with the mucosal lining of various other orifices in the body and suggested that its function was to assist in anal closure. As Staubesand et al. (1963) pointed out, a n erectile mechanism would greatly enhance such a property. The present study has shown that the submucosa does not form a continuous ring of thickened tissue in the anal canal but a discontinuous seriesof cushions, the three main ones being found constantly in the left lateral, right anterior and right posterior positions. Treitz (1853) also referred to cushions of tissue in the anal lining and noted that the submucosal smooth muscle contributes a great deal t o their bulk. In the present study the haemorrhoidal venous plexus was found to be congregated within the cushions as well, not forming a uniform network around the anal canal. The dilatations of the veins obviously enable the cushions t o vary considerably in size. The segregation of the submucosal pad into separate cushions seems an ideal arrangement for adapting the anal canal lining to great changes in size of the lumen. The importance of the cushions may be judged from the fact that they are formed early on in embryonic life, as the illustrations in Johnson’s (1914) paper on the development of the anorectum testify . 549

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Fig. 12. a , Anal varices in a patient with portal hypertension due to cirrhosis of the liver. 6, Prolapsed piles.

What are haemorrhoids ? The varicose vein theory: Stemming from the assumption that the dilatations of the veins of the internal rectal venous plexus are the result of a pathological change, the varicose vein theory is shown to be invalid by the confirmation that the dilatations are in fact normal. Furthermore, there is no evidence of a restriction of venous drainage from the anus or of a high venous pressure developing there. The fact that piles are no more common in patients with portal hypertension than in the population at large (Hunt, 1958) is additional evidence against the theory, as is the fact that,when anal varices occur as the result of portal hypertension (a rare event) the appearance is quite different from that of haemorrhoids (Fig. 12). The varicose vein theory also fails to account for the fact that piles are frequently single and more common in the right anterior position than elsewhere (Goodsall and Miles, 1900). The vascular hyperplusiu theory: The present histological studies, like those of Graham-Stewart (1962), suggest that haemorrhoidal bleeding comes not from the venous spaces (‘arterialized’ by direct communications or not) but from dilated capillaries in the lamina propria. Furthermore, although dramatic descriptions of haemorrhage are often given, only 1 patient in the present study was anaemic at the time of admission, and Graham-Stewart found only 1 patient to be anaemic in his series of 150 haemorrhoid sufferers. Although it is generally taught that bleeding is the first manifestation of piles (Gabriel, 1963; Goligher, 550

1967), there appears to have been no study, apart from the present one, which has been aimed at examining this dictum. The present findings suggest that bleeding is usually the later symptom and probably secondary to prolapse. There is, therefore, neither histological nor circumstantial evidence to support the vascular hyperplasia theory. The sliding anal lining theory: The discovery of the anal canal to be lined by specialized highly vascular cushions of submucosal tissue provides substantial support for the sliding anal lining theory. It would account for the regular appearance of piles in the right anterior, right posterior and left lateral positions and for their naked eye and histological appearances. Accepting that the cushions contribute to the mechanism of anal closure, it accounts for the high percentage of people who experience an impairment of continence after haemorrhoidectomy (Bennett et al., 1963). The triradiate configuration of the anal lumen due to the cushions might also explain the conflicting measurements of anal force as differently estimated by means of a force gauge and a balloon (Collins et al., 1967). That piles have been found to be associated with straining and an irregular bowel habit (Hyams and Philpott, 1970) is also compatible with the sliding anal lining theory. An irregular bowel habit is likely to be associated with hard and bulky stools, causing straining, which would be more likely to push the cushions out of the anal canal. Furthermore, straining, by producing a general increase in venous pressure, may cause engorgement of the

The nature of haemorrhoids cushions during defaecation, making their displacement more likely. Treitz’s muscle might become stretched and disrupted if repeatedly subjected to such forces, intermittent and then permanent prolapse of the cushions resulting. Perhaps the right anterior cushion is subjected to a greater downward force during defaecation than the others, accounting for its more frequent prolapse. Anal compliance may also be a factor in the production of haemorrhoids and may be associated with diet and stool consistency, accounting for the geographical distribution of the condition (Burkitt, 1972). If the anal canal is narrow and relatively rigid the cushions would be more likely to be pushed out o n defaecation (perhaps helping to explain the success reported for forcible anal dilatation (Sames, 1972) in the treatment of piles). Once prolapsed, the venous drainage from a haemorrhoid may be impeded by anal closure on the superior and middle rectal tributaries and by kinking of the inferior ones. The pile (displaced anal ‘cushion’) would then become engorged and therefore more difficult to replace. Such a situation may predispose to thrombosis-an ‘attack of the piles’. The success accorded to injection (Goligher, 1967) and banding (Barron, 1963) in the treatment of prolapsing piles is probably attributable to fibrosis in the cushion and a reduction in its size respectively. In summary, the available evidence suggests that the theory that piles are nothing more than a sliding downwards of part of the anal canal lining is probably the correct one.

Acknowledgements I would like t o thank M r T. Rowntree, M r J. D. Jenkins, D r J. Guthrie and the staff of the Morbid Anatomy Department, Southampton, Professor Sir James Fraser and the Wessex Regional Health Authority; without their help and encouragement this work could never have been undertaken. References

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