Paper - The relative frequency of the various positions of the vermiform appendix (1924)

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Gladstone RJ. and Wakeley CPG. The relative frequency of the various positions of the vermiform appendix - As ascertained by an analysis of 3000 cases: with an account of its development. (1924) Brit. J. of Surgery. 11(43):

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This historic 1924 paper by Gladstone and Wakeley is a description of the vermiform appendix.

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The Relative Frequency of the Various Positions of the Vermiform Appendix - As ascertained by an analysis of 3000 cases: With an account of its Development

By Reginald J. Gladstone and Cecil P. G. Wakeley, London.

A great deal has been written concerning the position of the caecum and appendix; but notwithstanding the excellent work which has already been done, there is a general feeling that the individual experience of many surgeons and anatomists does not conform with the statements that have been published and accepted with regard to the relative frequency of the different positions assumed by these organs. It was on this account that in 1914 we commenced making careful observations upon the position of the appendix as seen in the operating theatre, post-mortem and dissecting rooms, and by the middle of this year the total number of cases in which the position of the appendix had been recorded amounted to 3000. The cases will naturally include, in addition to those in which the normal position was unaffected by inflammatory adhesions or traction bands, the usual cases which are likely to be met with in surgical practiee—-for example, the acute and chronic cases of appendicitis. VVe have, however, thought it unnecessary to complicate the classification by introducing accidental factors into the statistics. The position of an abscess is most likely to be determined by the original position of the appendix and the surrounding folds of peritoneum, and the influence of inflammation in altering the normal position of the appendix is not of sufficient importance to interfere with the general value of the statistics which we have collected. One of the objects we have had in view has been to afford an explanation of the various typical positions in which the caecum and appendix are found, and we have thus examined a series of human embryos and foetuses up to the time of birth and included a description of the changes which they undergo during this period.

As the position of an inflamed or gangrenous appendix and its relationship to adjoining parts frequently determine the site of an abscess, it is important that the surgeon should have some knowledge of the relative frequency of the various situations in which the appendix may be found and its relationship to the surrounding pouches and folds of peritoneum.

A good deal of misconception arises out of the use of certain terms in regard to the folds of peritoneum and fossae around the caccum and appendix.

As it is of the greatest importance that these names should denote a definite condition, we have thought it necessary at the outset to define clearly what we understand by the terms employed in this article. The terms which we propose to use are given in the following table, and details with regard to the exact position of the appendix and the peritoneal folds and fossat follow.

Table Showing Positions of the Appendix, with their relative frequency

(table to be formatted)

3000 b 1000 I


1. Anterior or pre-ileal . . . . . . . . 27 0.9

2. ‘ Splenic ’ or post-ileal . . . . . . . . 15 05

3. ‘Pelvic’; on psoas muscle, near or hanging over the brim of the pelvis .. .. .. , 825 27'5

4. Sub-cazcal, beneath the ‘ caput cseci ’ . . ‘ 56 1-86

5. Post-caecal and retrocolic l 2076 69-2 6. Ectopic 1 1 0035 |

1. The Anterior or Pre-ileal Position (Fig. 290) is uncommon (0.9 per cent). The appendix is directed upwards a11d forwards towards the abdominal wall, and also medially in front of the terminal part of the ileum. The meso-appendix is unusually long; its free edge is directed upward and the appendicular border is to the right. The original posterior surface is thus turned forward and the anterior backward, so as to cover over the ileoceecal fossa, which may become obliterated as is shown in the drawing.

Should the organ become inflamed it may form adhesions to adjacent coils of small intestine, and an abscess may form between these coils and the appendix. Generally, however, the great omentum is early on the scene, and often completely surrounds the appendix ; in this case the inflamed mass may be felt on abdominal palpation.

In the case represented in Fig. 290, two lobulated folds of peritoneum containing fat extended upward one on each side of the appendix from root to tip. There was a well-marked genitomesenteric fold extending from the ileum, where it was attached to the left side of the meso-appendix, down to the margins of the aperture of a hernial sac. The sac was empty, about one inch in length, and its opening lay to the inner side of the origin of the deep epigastric artery, which vessel crossed above the neck from the outer to the inner side, and thus closely encircled the orifice of the sac in about twothirds of its circumference. The hernial sac, although ‘internal’, was oblique in position, and it did not appear ever to have contained any viscus. A lobulated mass of fat which occupied the lower part of the inguinal canal was adherent to its external surface and must have exerted traction on the peritoneum, drawing it downward into the canal. The ‘caput caeci’ descended to within one inch of the hernial orifice, and the outer and lower border of the caecum was bound down to the outer end of Poupart’s ligament and the iliac crest by four or five short parietocaecal folds of peritoneum. The posterior surface of the caecum was directly adherent to the floor of the iliac fossa. The terminal part of the ileum was directed downward at its junction with the caecum so as to form an acute angle with the ascending colon. At the point of attachment of the genitomesenterie fold there was a sharp bend with the convexity directed upward, and the ileum proximal to this was considerably dilated, and contained solid faecal matter. The specimen, therefore, forms a marked contrast to the case represented in Fig. 292, in which the ileum was kinked in a downward direction, and the tip of the appendix was also directed downward. In both'cases the ileum was held above and below by strong peritoneal bands; 111 Fzg. 291 it appears that the upper band had obtained the mastery over the lower band ; while in Fig. 292 it would appear that the lower of the two contending forces was the stronger. Both cases were found in old dissecting-room subjects, and the constriction of the ileum appeared to have been of long standing.

FIG. 290. Pre-ileal position of appendix. Observed in an aged male subject, in whom there was a well-developed genitomesenteric fold, connected below with the orifice of 3. hernial sac and the right ‘ plica hypogastrica ’ ; above, it was attached to the root of the appendix and its mesentery, and also to the terminal part of the ileum, which was kinked in an upward direction opposite the attachment of the fold. The part of the ileum proximal to the kink was distended with gas and hardened faeces.

Ap., Appendix caeci. BL, Bladder. G.M.F., Genitomesenteric fold. H.P., Orifice of hernial pouch. I.Ap.F., Ileocsecal fold. I.C’.F., Ileocaecal fossa. I.Ep.A., Fold raised by inferior epigastric artery. Il., Distended ileum. M.Ap., Meso-appendix. P.C., Pelvic colon. P.H., Plica hypogastrica.

2. The ‘splenic’ or Post-ileal Position is still more uncommon; only 15 (025 per cent) were observed in our 3000 cases. The appendix passes upward and to the left beneath the mesentery, or it may be curled up in the ileocaecal fossa (Fig. 291) under cover of the terminal part of the ileum and the ileocaecal or ‘bloodless’ fold of Treves. In the specimen figured this fold was loaded with fat, and, like the ileum, it has been drawn upward in order completely to expose the appendix. The appendix and its mesentery were adherent to a well-marked genitomesenteric fold, to the right of which was a parietocaecal band which passed upwards behind the ‘caput caeci’ to the root of the appendix. A narrow and deep recess lay between the genitomesenteric and parietocaecal folds, which we regard as a subdivision of the post—ca:cal fossa. In the ‘splenic’ type of the post-ileal position of the appendix, where the tip is directed upwards and to the left beneath the mesentery, there is a likelihood, should inflammation occur, of the appendix becoming adherent to the mesentery, and setting up mesenteric thrombosis. Should the appendix be retroperitoneal it may lie behind or even within the root of the mesentery (intramesenteric position). In such cases, if inflammation occurs, mesenteric thrombosis is almost inevitable.

3. The ‘ Pelvic’ or Descending Position is quite common, 27-5 per cent in our series. In this type the appendix passes downwards on the psoas muscle and may overhang the brim of the pelvis. The meso-appendix is usually long, and there,’ is often a genitomesenteric fold, lying medial to the appendix and its mesentery. This is usually attached to the ileum or the under surface of the mesentery of the small intestine about three inches from the ileoczccal

Fig. 291. Post-ileal position of appendix. From an old dissecting-room subject, showing the tip of the appendix lying in the ileocaecal fossa. The ileo-appendieular fold is loaded with fat, and with the terminal part of the ileum has been drawn upward, so as to expose the appendix. A subcaecal fossa is divided by a parietocaecal fold into an outer part lodging the caecum, and an inner which is bounded medially by a genito valve (Fig. 292). In this specimen there Was a marked constriction of the ileum and a kink in the downward direction, so that the terminal part of the ileum ascended to the ileoczecal mesenteric fo1d valve. The mesenteric attachAp Appendix. G.M.F., Genitomesenterio., ment of the meso-appendix had fold. I.Ap.F., Ileocaecal fold. I.C.F., Ileocaecal fossa. P.C'.F., Parietocaecal fold. In Consequence been drawn downwards with the terminal

part of the ileum, and the descending position of the appendix had thus been rendered possible. In Fig. 290, showing the ascending or pre-ileal type, the reverse condition is present, the meso-appendix is drawn upward with the ileum, which in this case descends from an upwardly-directed kink to the ileocaecal valve. In the example shown in Fig. 292 of the descending type it will be seen that there is great distension of the ileum on the proximal side of the constriction, and also that the testes are incompletely descended. The penis and scrotum are small, and the pubic hair scanty. The lower end of the genitomesenteric fold is subdivided into an ill—defined ridge continuous with the fold raised by the obliterated hypogastric artery and a fold running towards the internal abdominal ring.

If inflammation should occur in an appendix overhanging the pelvic brim in the female, it may become adherent to the right ovary, and pain may occur In the right iliac fossa during menstruation. An inflamed appendix sometimes becomes adherent to the bladder or rectum, and in such cases painful micturition or defazcation may occur; and should an appendicular abscess form, it may discharge into the bladder or rectum.

Fig. 292. Descending position of appendix. The appendix is directed downwards, and lies on the right psoas muscle. Its tip overhangs the brim of the pelvis and is in relation with a. tortuous external iliac artery. A well-developed genitomesenteric fold is present, which has caused a downward kink and constriction of the ileum. The portion of ileum proximal to the constriction was tensely distended with flatus. The testicles were incompletely descended, and the external genitalia small.

Ap., Appendix. 0., Constriction of ileum. G.JlI.F., Genitomesenteric fold. I.Ap.F., Ileocaecal fold. I l., Distended portion of ileum. I l.C., Iliac colon. 1M.Ap., Meso-appendix. P.C'.F. Parietocaecal fold.

4. The ‘Sub-caacal’ Position of the appendix beneath the ‘caput czeci’ (Fig. 293) is not so uncommon as one might be inclined to think—1-86 per cent in our cases. The appendix lies in the lower part of the iliac fossa, and is usually turned to the right. It is often coiled or kinked. The ileoappendicular fold is usually small or absent. In the specimen drawn a sharply-defined fold of peritoneum passed from the posterior surface of the ileum to the lower part of the iliac fossa, where it terminated above and to the outer side of the external abdominal ring. It limited the sub-eaecal fossa below and internally, and probably represented a genitomesenteric fold, the upper end of which had descended with the ileum, so that the direction of the band had been changed from the vertical to the horizontal. The terminal part of the ileum in these cases is frequently found ascending from the pelvis to the ileoeaecal junction, and having a direction which is in line with the ascending colon. If inflammation occurs in the appendix in this position, an abscess may form, which sometimes bursts through the fascia iliaca into the iliacus muscle, and gives rise to flexion of the hip-joint owing to spasm of the muscle. A variety of post—caecal fossa containing the appendix has been described beneath the iliac fascia. This we consider to be produced as a secondary result of inflammation.

5. The ‘ Post-caacal’ and Retrocolic Positions. The group including these positions is the most common in our series, there being 2076, or 692 per cent, This is in accord with the general experience of both surgeons and anatomists at the present time, but differs markedly from the statistics which have been published by previous writers and quoted in many of the standard text-books. This may be accounted for partly by the difficulties which arise from one group overlapping another, and partly from the subdivision of the posterior positions, which are essentially the same, into two or more groups, thus masking the true frequency of this most common type.

The appendix may be found -

a. Free in a post-caecal or retrocolic pouch of peritoneum.

b. Held in contact with the caecum or the ascending colon by a short mesentery. c. Adherent to the caecum or colon, which, with the appendix, form the anterior wall of a retrocolic pouch of peritoneum. d. Behind the caecum and ascending colon, but, owing to obliteration of the retrocolic‘ pouch, entirely extraperitoneal.

Fig. 293. Sub-eaecal position of appendix. The appendix lies under cover of the ‘ caput caeci ’ in a post-csecal fossa, which is limited below by a. horizontally placed genitomesenteric fold.

.41)., Appendix. G‘.M.F., Genitomesenteric fold. 11l.Ap., Mesentery of appendix.

There is no doubt that inflammatory changes occurring in the appendix may cause a perfectly free appendix in position (a) to become adherent to the caecum and so come into sub-division (c). There is also, however, a considerable amount of variation in the degree to which the eaecum and ascending colon become adherent to the posterior abdominal wall and iliac fossa in the course of normal development, apart from any secondary adhesion caused by inflammation.

As an aceura.te knowledge of the position of the appendix, and of the various foldings of the adjacent parts of the peritoneum during foetal life, are essential for the explanation. of the fixation of the caecum and appendix in the normal positions in which they occur in the adult, and more especially of some of the more unusual sites of the appendix such as the intramesenteric or extraperitoneal, we have considered it necessary to describe in some details the various phases of its development from its first appearance until birth. The unusual positions referred to may not only give rise to difficulty in finding the organ, but may predispose to obstruction, kinking, and inflammation, and a knowledge of the developmental aberration or defect which has produced a particular condition will prove of the greatest value in dealing with the condition quickly and effectively.

Fig. 294. A linear reconstruction from serial sections of a human embryo, 9 mm. in length, aged about 4.5 weeks. The embryo is seen at 9. magnification of 15 diameters. There were 407 sections, 10 ft. in thickness. Every second section was drawn, and the parts shown in the drawing were plotted on ‘ millimetre paper ’. The figure shows the cephalic or proximal limb of the umbilical loop of the intestine lying to the right of the caudal or distal limb, which it crosses near the thickening which marks the position of the future camoappendix and ileocaacal junction. The vitello-intestinal duct or stalk of the yolk-sac is attached to the summit of the umbilical loop.

1, Notochord. 2, Internal carotid artery. 3, Tongue. 4, Mandibular arch. 5, Ophthalmic artery. 6, Anterior cerebral artery. 7, Posterior cerebral artery. 8, Third arch. 9, Fourth arch. I0, Aorto-pulmonic trunk. 11, Allantois. 12, Vitelline duct. 13, Umbilical artery. 14, Cloaca. 15, Urethro-vesical tube. 16, Rectum. l7, Ureter. 18, Renal bud. ]9, Middle sacral artery. 20, Umbilical loop. 21, Cephalic limb. 22, Caudal limb. 23, Mesonephric duct. 24, Abdominal aorta. 25, Gall—bladder. 26, Left or dorsal pouch. 27, Right or ventral pouch. 28, Stomach. 29, Right lung. 30, Subclavian artery. 31, Trachea. 32, (Esophagus. 33, Pulmonary artery. 34, Sixth arch. 35, Primitive vertebral artery. C’. .42., Coeliac axis. S.M., Superior mesenteric artery.

The early stages of development have been admirably described by Kelly and Hurdon in their work on The Appendix Vermifomnis and its Diseases, 1905. This description is based on an investigation of 54 human embryos from the private collections of the late Franklin P. Mall and M. Max Brodel. We shall therefore merely allude to certain points of general interest which have been observed by us during its extra-embryonic stage, and shall describe more fully the later phases of its development, from the return of the intestine from the ‘umbilical coelom’ into the abdominal cavity until birth.

The first indication of the ileocaecal junction occurs in embryos from 5 to 5.5 weeks old and from 5 to 7.5 mm in length. The intestine then projects forwards into the root of the umbilical cord, in the form of a wide V-shaped loop. The proximal part of this loop is continuous with the duodenal end of the foregut, and is termed the cephalic limb; the apex projects forward within the umbilical extension of the peritoneal cavity or umbilical coelom into the root of the cord, and is continuous with the stalk of the yolk-sac; the distal part of the loop is continued into the hind-gut, and is termed the caudal limb. The loop is connected with the posterior wall of the abdomen by a dorsal mesentery, which is attached to this wall along an approximately medial line. It contains the omphalomesenteric or Vitelline vessels, which will afterwards be represented by the single superior mesenteric artery and vein. Near the distal end of the caudal limb of the loop a slight bulging is present, which is the first indication of the caecum and appendix, and of the junction of the small with the large intestine.

Fig. 295. Two stages illustrating the lifehistory of the ‘ transient appendix ’, after Max Briidel and Mall, from The Appendix Vermiformis and its Diseases (Kelly and Hurdon). A represents an early phase in its development dur ing the 6th week, B an atrophic stage preceding its degeneration and disappearance from a 7-weeks embryo.

In an embryo of 9 mm length, which has been reconstructed from serial sections by one of us (R. J. C.) after the linear projection method (Fig. 294), the loop of intestine is seen to project considerably farther forward into the umbilical cord, and has become twisted so that the caudal limb lies to the left and nearer the head end of the embryo, while the cephalic limb is to the right and nearer the tail. The stalk of the yolk-sac is now reduced to a narrow tube, the vitello—intestinal duct, which is attached to the summit of the loop, and at this stage helps to hold it in position. Between the 6th and 7th weeks, in embryos of from 10-mm. to 20-mm. length, a considerable elongation of the caecal bulging takes place, and its longitudinal axis, at first straight, and in line with the longitudinal axis of the colon, usually becomes bent so as to form a U-shaped figure with the commencement of the colon.

This is apparently the result of traction exerted on the caeco—appendix by its mesentery, which is drawn out from the common mesentery as the caecum elongates. A remarkable outgrowth from the tip of the caecum is also present at this stage of development (Figs. 295 and 296), which simulates in its position and form the true vermiform appendix; but since it atrophies in embryos of 20-mm. length, and afterwards completely disappears, it is believed to be an independent structure, and not connected with the permanent appendix caeci, which is differentiated later. Possibly it represents one of the two czecal diverticula which are found in birds, and appears only as a vestigial and transitory structure in the human embryo, whereas the other develops later and persists as the permanent ‘appendix caeci’. In the succeeding 8th and 9th weeks, the part of the umbilical loop which gives rise to the small intestine increases enormously in length and becomes massed in coils beneath the caeco-appendix and commencement of the colon, which lie above and to the left. The return of the intestine from the umbilical coclom into the abdominal cavity takes place in embryos of about 40 mm. length and 10 weeks of age. The small intestine slips back first and occupies a position to the right of the intra-embryonic mesocolon, while the caeco-appendix with the commencement of the colon, which lie above the small intestine in the umbilical coelom, return last, and assume a sub hepatic position near the middle line, below and to the right of the umbilical vein.

Fig. 296. Transverse section through the umbilical cord of a human embryo 20 mm in length, obtained from a 1aparotomy performed by Mr. Sidney Boyd. The ‘transient appendix’, T.Ap., is seen to the left (right side in the drawing, the section being seen from in front) of the umbilical loop of intestine and its dorsal mesentery. No lumen is present, except at its root, where it springs from the cascaappendix. The appendix is directed forward away from the embryo, and the portion of the distal limb of the loop, D.L., below and to the right of it is the terminal part of the ileum. (Compare Fig. 998.)

Al., Allantois. D.L., Distal limb of umbilical loop, cut near the termination of the ileum. L. U. V., Left umbilical vein, already greatly exceeding the right umbilical vein, R. U.V., in size. M ., Mesentery of small intestine containing branches and tributaries of the superior mesenteric artery and vein, S.M. In this position these vessels are incorporated in the mesentery, lying between its two layers; farther forward in the region of the vitello-intestinal duct they lie, like the vitelline vein, V.V., free in the umbilical coelom. P.L.,P.L— Proximal limb of umbilical loop. T.Ap., Transient appendix. U.A., Umbilical arteries. U.O., Cavity of umbilical coelom. W.J., VVhartonian jelly.

The mechanism of this return of the alimentary canal into the abdominal cavity, and the relative positions which are subsequently assumed by the large and small intestines, have been well described by Professor J. E. Frazer and Dr. R. H. Robbins in an article entitled “ Factors concerned in causing the Rotation of the Intestine in Man.”

The typical relations of the caeco-appendix soon after the return of the intestines into the abdomen are well seen in Fig. 297, which is a drawing, taken from in front, of a model reconstructed by one of us (R.J. G.) according to the wax-plate method of Born, from serial sections of a 45 mm human embryo. The position of the liver is indicated by an interrupted line. It will be seen that the caeco-appendix has moved to the right of the median plane and lies under cover of the right lobe of the liver. It is coiled in the form of a fl-shaped bend. The proximal limb of the loop runs upward from the ileocaecal junction behind the colon ; it then turns backwards formintr the 5 a summit of the fl-shaped bend, and finally downward as the descending limb which terminates in a free ex tremity, the tip of the appendix, which appears just below the inferior border of the liver. It is situated just below the ileocaccal junction, and above the highest point of the iliac crest, at the level of the body of the 4th lumbar vertebra. The differentiation of the caecum from the appendix has not yet taken place. It is probable, however, that the future caecum is represented by a slight bulge of the large intestine immediately below the ileocaecal junction, and that the whole of the fl-shaped bend will give rise to the appendix. The ileum passes forward medial to the caeco—appendix, and enters the colon from below and to the left (Fig. 299). Thus, the rotation of the ileocaecal junction from its primary position, which is on the right of the colon (Fig. 298), to its permanent position behind and to the left, has already taken .place. This rotation is due to the movement of the caeco—appendix from the median place in which it lies at the time of its entrance into the abdomen, in a direction downward and to the right, beneath the liver, combined with a movement of the terminal part of the ileum with its mesentery in the reverse direction from right to left. At this stage the lower part of the right lobe of the liver is lateral to the caeco-appendix (see Fin. 299) and the commencement of the colon, and coils of small intestine lie behind, and thus separate them from the posterior abdominal

Fig. 297. A, Drawing of a model, reconstructed from serial sections of a 4-5-cm. human embryo, showing the relative positions of the viscera in the upper part of the abdominal cavity. The outline of the liver, L., is represented by an interrupted line. It will be noted that the ascending colon, which is very short, lies entirely under cover of the liver, and in front of the lower part of the right kidney a. wide angle marks the position of the hepatic flexure of the colon, which lies between the c2eco~appendix and duodenum. Thence the transverse colon passes obliquely upwards and to the left, across the descending duodenum, head of pancreas, and commencement of the jejunum, to the left suprarenal body. Here it forms a loop behind the pyloric part of the stomach (splenic fiexure). This loop lies a considerable distance below the level of the spleen, which has not yet grown down to its permanent position relative to the left snprarenal body and kidney. The descending colon then passes obliquely downwards and to the right below the obliquely placed third portion of the duodenum. The ileocaecal junction lies just below the lower end of the right kidney, and is separated from the posterior abdominal wall by coils of ileum. The liver lies to the right and in front; coils of intestine lie in front of, as well as behind, the ezecum and appendix. (See Fig. 299, which is a drawing of a section from the series used in the construction of the model, taken just below the inferior pole of the right kidney.)

B represents the caecum and appendix, viewed from the right, and shows the n- shaped bend, the terminal part of the ileuul, and ascending colon.

Fig. 298. Drawing representing the lower half of the trunk and a. portion of the umbilical cord seen from above. Slightly modified from Frazer and Robbins. The figure shows diagrammatically the relation of the terminal part of the ileum to the caeco-appendix and the commencement of the colon. The caeco-appendix lies above the coils of the small intestine, and these authors believe that it is the last part of the loop to return into the abdominal cavity. This diagram should be compared with Fig. 296, which depicts a transverse section of the umbilical cord just beyond the tip of the caeco-appendix.

Fig. 299. A camera lucida drawing through the ileocsecal junction, from one of the sections of the 4-5-cm. embryo from which the model, Fig. 297, was reconstructed. The descending limb of the n-shaped czeco-appendix lies between the terminal part of the ileum and the right lobe of the liver, and coils of intestine intervene between the cz=ecoap endix and the posterior ab ominal wall. The descending colon and its mesentery (the future pelvic colon) are seen in front of the psoas muscle and ureter, and to the right of the latter are the sperrnatic vessels lying in the ‘ plica. vascular-is ’.

Ap., Appendix. Asc.O., Ascending colon. C'., Descending colon. Il., Ileum. Il.0., Ileocaecal orifice. P3,, Psoas major. Sp.V., Spermatic vessels. U., Ureter.

Wall and right kidney (F ig. 299) ; moreover, the attachment of the common mesentery of the small intestine and colon is still approximately mesial. In the duodenal region, however, the root of the mesentery is curved towards the right, and is continuous with the mesocolon, Where the mesenteric pedicle turns anti-clockwise round the axis of the superior mesenteric artery; the mesocolon thus crosses the head of the pancreas andthe descending part of the duodenum, as in the adult, though the omental bursa has not yet become adherent to the transverse colon a.nd its mesentery. Since coils of intestine intervene between the caeeo-appendix and the posterior abdominal wall, and there is a long mesocolon, the caecum is free to move in a downward direction into the iliac fossa. In the 45-mm. embryo from which the model has been reconstructed, it already lies just above the level of the iliac crest, although it is almost completely under cover of the right lobe of the liver. The position of St. the caeeo-appendix at this stage appears to vary considerably in different speci’_ AWQ mens. This is largely due to the degree I‘ 1 of rotation that has taken place at the

Av ileocolic junction; thus, in a 45-mm embryo figured by Frazer and Robbins, the ileum enters from the right side, and the appendix is directed upwards in front of it; in another specimen representing a later stage the ileum enters the colon from below, and the appendix is directed horizontally to the right; in our own specimen the rotation is complete, the ileum enters from behind and from the left (Fig. 297), and the appendix is retrocolic in position (Fig. 299). FIG’ 30°-—E°‘°P‘° P°Si‘i°“ 0‘ the Should coils of small intestine

caecum and appendix, from a dissecting _ . room subject in which the testes were remain between the right lobe of the

imperfectly descended. The csecum and ' . _ ' ' appendix were free, and displaced upwards hver and the C6800 appendlx’ thls’ wlth

and to the left beneath the stomach, in the proximal part Of the colon, may be pushed to the left (mg. am) and take between 3 and 4; the hepatic flexure lies up a position beneath the stomach and between 2 and 3 ; the splenic flexure at 4. 1 . . The loop formed by the‘ pelvic colon» transverse colon, with the tip of the remains in the foetal position, namely, in the lower Part of the abdomen and right appendix directed to the right and lying

iliac fossa; its course is represented by the below the proximal part Of the C0l0I],

dotted lines and arrows 5, 6, 7 ; it lay for ' . ‘ the most Pm behind the small intestine’ which courses horizontally from left to

except fora. small portion indicated by the right, instead Of ascending in the right

'fi:°:§g§:‘ivf’i::“fc?3s:'fd 7’ where ‘t °°°“p“’d lumbar region to the liver.

At this stage, immediately after the rotation of the terminal part of the ileum with its mesentery beneath the caecum and the proximal part of the colon, which are carried to the right, an angle is formed between the mesocolon carrying the right and middle colic arteries and the terminal part of the mesentery of the small intestine enclos ing the vasa intestini tennis; at the apex of this >—shaped bend is the ileocolic artery, which sends an anterior czecal branch in front of the ileocolic junction, and a posterior branch behind the ileum to the posterior surface of the cacco-appendix. This branch runs in the mesentery of the czeco-appendix and persists as the appendicular artery, which in the adult runs near the free border of the meso—appendix. Should the appendix become caught in the receding angle between the two laminae of the >-shaped fold, it will be held in are troperitoneal position at the root of the mesentery, (‘intramesenteric position ’*), or it may lie in the anterior wall of a retrocolic or retro-ileal pouch; and should the pouch become obliterated by adhesion and absorption of its walls, the appendix will be completely extraperitoneal. In the latter case it may be readily exposed bydividing the peritoneum below the caecum and carefully raising the ‘caput cwci’ fromthe iliac fossa. Connected with the lower surface of the mesentcric laminae of the >-shaped bend is an important fold of the peritoneum which runs vertically downwards to the brim of the true pelvis and vicinity of the future internal abdominal ring (Figs. 290-293 and 301). This fold has been described by various authors under different names, of which perhaps the best is the ‘genitomesenteric’. Its connections have been described by R. Douglas Reid in several articles recently published in the J oumal of Anatomy and Ph.y.9z'0l0g3/, and he believes it to he instrumental in causing the descent of the mesentery of the small intestine, with a consequent lowering of the mesenteric root; he also states that it is the commonest cause of a retrocolic position of the appendix. The fold is usually triangular, having an anterior surface directed forward and to the left, a posterior surface directed backwards and to theright. Of the three borders, two are fixed and one is free. Thus, there is usually a posterior fixed border attached to the posterior abdominal wall and extending from the duodenal region downwards on the right psoas muscle to the pelvis; an upper attached border connected with the under surface of the mesentery of the small intestine near the

Fig. 30l. Drawing of a dis section showing the caecum and appendix lying at the level of the right iliac crest, and the position of the colon and its mesentery in a foetus at the end of the third month. The small intestine has been removed so as to show the root of the mesentery and the mesocolon. The appendix was directed upwards behind the ileocaecal junction and ascendin colon. A genitomesenterio fol passed from the posterior aspect of the broad ligament and the brim of the true pelvis upwards over the ‘ plica hypogastrica ’ and right psoas major to the posterior aspect of the mesentery of the small intestine. It had a free border directed to the right, and a Wide basal attachment corresponding internally to the line of the ovarian vessels. Its lower part and root of attachment therefore correspond to the ‘ plica vascularis ’. A similar fold is present on the left side, which in the later stages of development would be covered and obliterated in the greater part of its extent by the growth over it of the pelvic mesocolon.

2112., Appendix. Bl., Bladder turned downwards with the anterior wall of the abdomen. G.M.F.,

Genitomesenterie fold. P.H., Plica hypogastrica. P. V., Plica vascularis (gin. beyond arrow).

ileocaecal orifice, or with the ileum in the same situation ; and a free border

An interesting example of the intramesenteric position of the appendix has been recorded by Nicola Novaro, in the Gaz. d, Osp., 1921, xlu, 147.

usually directed forward and to the right. The lower end of the fold in the female passes over the brim of the pelvis, on to the posterior aspect of the broad ligament of the uterus, and is frequently blended with the suspensory ligament of the ovary. In the male, it may end in the neighbourhood of the internal abdominal ring, or pass over the brim of the pelvis to the lower end of the fold raised by the obliterated hypogastri.c artery. The genitomesenteric fold may contain between its layers a thick stratum of extraperitoneal connective tissue, which in some cases forms a traction band of considerable strength; it may thus give rise to kinking and constriction of the terminal part of the ileum, or a displacement downwards and inwards of the ileum, and with it the caecum and appendix.

Various factors appear to be concerned in the formation of this fold. Of the folds which are present in the embryo, we may consider first the ‘urogenital mesentery’. This connects the genital gland and mesonephros (Wolflian body) to the posterior abdominal wall (Fig. 302). It is continuous at its upper end with the ‘plica vascularis’ or diaphragmatic ligament, and in the pelvic region is connected by the inguinal fold containing the gubernaculum with the internal abdominal ring. Following the degeneration which takes place of the upper part of the mesonephros and genital gland, there is also a degeneration and apparent displacement downwards of the diaphragmatic ligament as far as the origin of the internal spermatic or ovarian vessels

Fig. 302. Camera lucida drawing of a transverse section through a. 35-mm. human embryo, showing the relations of the testis and mesonephric fold to the duodenum, kidney, and liver.

1)., Duodenum. 1... Liver. M.D., which descend in the fold—now known Mullerian duct. M.N.F. Mesonephric . ‘ ' ‘ ’_ ‘ fem RX” Right kidney: RU” Right as the phca Vascularls to the testicle ureter. T., Testis. .s'.V., Internal or ovary. The lower end of the fold

%',gigé;) Iéf1‘g%f3”‘°"‘1 persists in the adult female as the ovariopelvie ligament, or suspensory ligament of the ovary, with which the genitomesenteric band is frequently incorporated; and in the male passes downwards on the external iliac vessels to the internal abdominal ring, with which the lower end of the fold is sometimes associated, as in a case of patent ‘processus vaginalis’ in an adult male described by Douglas Reid* in 1913. In this case, as in the specimens represented in Figs. 290, 291, and 293, the genitomesenteric fold formed the left boundary of a retrocolic fossa. In Reid’s case, the appendix, which was in contact with the right or posterior surface of the ‘plica genitomesenterica’, could not be withdrawn from the fossa on account of an adhesion of its mesentery to the genitomesenteric fold. On the left side, the upper part of the ‘plica vascularis’ is, in the normal course of development, obliterated by the adhesion of the left side of the primitive mesocolon to the peritoneum covering the posterior abdominal wall. When the descending and iliac portions of the colon are carried to the left by the pressure of the enlarging coils of small intestine which fill the concavity of the n-shaped curve of the colon, the ‘plica vascularis’ is completely covered over by the mesocolon, and disappears. A similar obliteration of the upper part of the ‘pliea Vaseularis’ takes place on the right side, owing to the folding over of the mesentery of the ascending colon and terminal part of the ileum, and its adhesion to the peritoneum‘on the right side of the posterior abdominal wall. On the right side, however, the obliteration is not so extensive, owing to the lower attachment. of the mesentery of the small intestine being at a considerably higher level than that at which the iliae colon crosses the brim of the pelvis to become continuous with the pelvic colon on the left. The primary position of the plica is well seen in Fig. 301, in which the colon is still almost medial in position. The small intestine has been cut away so as to show the relation of the upper end of the genitomesenteric fold to the posterior surface of the mesentery of the small intestine. It will be seen to cross the fold raised by the hypogastrie artery, and the free border is directed to the right. The relationship of the ‘plica vaseularis’ to the posterior abdominal wall in a 4-5-cm. human embryo is well seen in Fig. 299. It lies in front of the psoas muscle, and contains the spermatic vessels between its layers. The position of the urogenital fold and internal spermatic vessels at an earlier stage (35 mm.) is shown in Fig. 302, in which adhesion has not yet taken place. It will be observed that the genital gland and mesonephric fold are connected to the posterior abdominal wall by a thin mesentery, which, as it is common to the genital gland and mesonephros, is termed the ‘urogenital mesentery’. The testis is lying in the same horizontal plane as the permanent kidney, liver, and duodenum. Sections of the spermatic vessels are cut across in the hilum (mesogenitale) of the testis, and to the right is seen the degenerating Miillerian duct, lying in the free border of the tubal part of the fold. The Wolffian duct and some of the epigenital tubules of the mesonephros are cut across in the glandular part. Felix has shown that the apparent descent of the genital glands, mesonephroi, and Wolffian ducts in the early stages of development is due to a degeneration of the upper (cranial) portion, which occurs simultaneously with the growth of the lower (caudal) pole. Accompanying this degeneration of the structures contained in the urogenital fold is a descent of the diaphragmatic ligament as far as the level of the lowest 9 to 11 pairs of mesonephric arterieswhich are present in a l9—mm. embryo, and which are represented in the adult by the internal spermatic or ovarian arteries; these are contained in the urogenital fold, and extend from their origin from the abdominal aorta, at the level where this vessel is crossed by the duodenum, to the genital gland. The fold of peritoneum in which they lie is now spoken of as the ‘plica vascularis’; this corresponds in its upper part, where it lies on the psoas muscle, to the line of attachment of the genitomesenterie fold, and ends below in the genital gland. It appears probable, therefore, that the genitomesen terie fold originates from that part of the urogenital fold which contains the definitive internal spermatic or ovarian arteries. The position of the spermaticvessels on the psoas muscle as seen in Fig. 299, and the appearance of the border of a peritoneal fold to the outer side of these vessels, give the impression that degeneration of the urogenital fold above the level of the testis has not been complete, and that the fold has become adherent to the peritoneum covering the psoas muscle. At a later stage of development the mesentery of the terminal part of the small intestine and commencement of the colon will adhere to this part of the peritoneum, which, should the view expressed above be correct, affords a ready explanation of the relation of the upper end of the‘ genitomesenteric fold to the posterior surface of the mesentery of the ileum in this position, and its connection below with the suspensory ligament of the ovary or-~in the male—~vthe upper end of the inguinal canal.

The upper part of the genitomesenterie fold thus appears to originate from an adhesion of the ileac mesentery to the right ‘plica vascularis’ and remnant of the mesonephric fold; and its lower part appears to be related in the male subject to the inguinal ligament and gubernaculum testis, and in the female to the suspensory ligament of the ovary. It is probable also, as has been suggested by R. Douglas Reid, that by its traction on the ileum the band is instrumental in causing the descent of the czccum and appendix into the right iliac fossa.

The strong bands that are sometimes present in this situation in adult and more especially aged subjects (Figs. 290 and 292), and which may give rise to kinking and obstruction of the ileum, are obviously due to an abnormal development of fibrous and muscular tissue within the normal fold. The abnormal development or hypertrophy of the sub— or extra-peritoneal tissue may be explained, as has been demonstrated by Arbuthnot Lane, on the assumption that forces, such as peristaltic action, or gaseous distension of the intestine, exert traction which is resisted by the development of a band which will act as a counteracting force in the opposite direction. Should these forces, as frequently happens, be exerted along the line of the normal fold as described above, this fold will become exaggerated, and the extraperitoneal tissue between its layers will become hypertrophied and condensed so as to form a strong ‘retention band’ capable of causing displacement and obstruction of the intestine.

We do not propose in this paper to describe variations in the form of ‘the caeeum and appendix, nor to refer further to peculiarities in the position of the various folds and fossae associated with this region. These have been ably and exhaustively described by various authors, reference to whom, along with detailed descriptions, will be found in articles by Sir Frederick Treves, Douglas Reid, and in Kelly and Hurdon’s The Vermiform Appendix and its Diseases.

Among the rarer conditions of the caecum and appendix which are of surgical interest, we may, however, refer to two important abnormalities, namely : (1) Congenital absence of the appendix; (2) Its position in the left iliac fossa in transposition of the viscera. An example of the former was described by one of us, in 1916, in the Journal of Anatomy and Physiology. The condition is extremely rare. No instance of it has occurred in the 3000 cases on which our classification has been based; and in another series of 1352 systematic observations, only one example, recorded by Fawcett and Blatchford, occurred. Several other cases, however, have been published or preserved in museums. These illustrate arrest of development at different stages, namely : “ Absence of the caecum and appendix ” (Robinson). “ Rudimentary czecum without appendix” (Sutton and Chill). “Blunt, conical caecum without appendix ” (Huntington). “ A caecum having a rounded symmetrical form, with the longitudinal muscular bands converging towards its apex, but without appendix ” (Huntington). “ Asymmetrical form without appendix ” (Gladstone).

The position of the caecum and appendix in the left iliac fossa associated with general transposition of the viscera, although rare, is of sufficient practical importance to merit a brief notice in this article. As was the case in absence of the appendix, no instance of this abnormality has occurred in our 3000 observations. One of us, however, when a student attending the Pathological Department of the General Hospital, Vienna, met with an example of general transposition of the viscera in a female child, age 18 months, who died from pyaemia secondary to scarlet fever, and through the kindness of the acting Professor of Pathology, Herr D’A1brecht, was enabled to obtain the specimen for the Middlesex Hospital Museum. It presented the ordinary characters of complete transposition; the caecum and appendix, however, lay at the level of the iliac crest uudcr cover of the large left lobe of the liver, as they had not fully descended into the left iliac fossa.

Apart from these cases of transposition of the viscera, ectopic positions of the caecum and appendix may usually be explained under one of the following headings: (1) Arrest of their descent towards the right iliac fossa. (2) Continuation of their descent beyond the normal limit, into the pelvis or into a hernial sac. (3) Deflection to some abnormal position——usually to the left—-associated with a failure in the adhesion of the ca.-cum and ascending colon to the posterior wall of the abdomen, and retention of the primitive dorsal mesentery.

In addition to the above-mentioned congenital causes of ectopia, displacement may occur as the result of a loaded caecum, giving rise to a low pelvic position, and other pathological conditions such as visceroptosis.

In concluding this account the authors consider that a brief reference is necessary to the statistics dealing with the position of the appendix by previous observers, which appear to differ markedly from their own series. In some cases this may be explained by different methods of classification. For example, M. Lafforgue (Anatom/is Humaine, Testut), from an examination of 200 cases, of all ages and both sexes, records the following percentage of frequencies :—

Ascending type . . . . . . 13 per cent

Descending type . . . . . . 41 '5

Lateral and internal type . . . . 26

Lateral and external type . . . . 17 ,, 97'5 ,,

Of his atypical rare cases, the appendix was twisted round the ileum in one case, and round the caecum in another

The classification is here based on the direction of the tip or longitudinal axis of the appendix, rather than on its position relative to the ileum, caecum, pelvic brim, or peritoneal fosszc. In comparing these figures with the authors’ series, it is probable that the 13 per cent grouped together in Lafforgue’s ascending type would have included, in addition to the authors’;ip1'e-ileal and ‘ splenic ’ or post-ileal types, a considerable number of the post-caecal and retrocolic cases in which the tip of the appendix happened to have been directed upwards in a retrocolic fossa. The descending type (~11-5 per cent) would have included, in addition to the authors’ ‘pelvic’ or descending type, a certain number of the sub-caecal and post-caecal types. The discrepancy, therefore, is obviously not so great as might be supposed.

From the clinical standpoint, however, the classification of the position of the appendix adopted in this article appears to be the more practical, since the appendix is often coiled or kinked (Figs. 29] and 293), and also since, from the surgical standpoint, the relations are often essentially different. For example, an ascending pre-ileal appendix, lying free in the peritoneal cavity, is totally different from an ascending retrocolic appendix confined in a fossa behind the colon, or perhaps extraperitoncal. In conclusion, We wish to emphasize the frequency with which we have found the appendix lying in the post-caecal and retrocolic positions, namely, in 69-2 per cent of the total number of 3000 cases. We regard this, therefore, as the typical and most common position of the appendix, and the descending or ‘pelvic’ type as the next in order of frequency.


CONNELL, F. G., “ Etiology of Lane’s Kink, Jackson’s Membrane, and Cazcum Mobile”, Surg. Gynecol. and 0bst., 1913, April, 353.

EASTMAN, J. R., “The Foetal Peritoneal Folds of Jonesco, Treves, and Reid, and their Probable Relation to Jackson’s Membrane and Lane’s Kink ", Surg. Gynccol. and 0bst., 1913, April, 341.

FELIX, W., Manual of Human Embryology, Keibel and Mall, 1912, ii, 823, 940.

FRAZER, J. E., and ROBBINS, R. H., “ On the Factors Concerned in Causing Rotation of the Intestine in Man ”, Jour. of Anal. and Physiol., 1915, 1, 75.

GLADSTONE, R. J ., “ Congenital Absence of the Appendix Vermiformis ”, Jour. ofiAnat. and Physiol., 1916, xlix, 4-14.

HURDON, E., vidc KELLY, H. A.

KELLY, H. A., and HURDON, E., The Vermzform Appendix and Its Diseases, 1905.

LANE, ARBUTHNOT W., The Operative Treatment of Chronic Intestinal Slasis, 1915, 3rd ed.


MAYO, C. H., “ Intestinal Obstruction due to Kinks and Adhesions of the Terminal Ileum”, Surg. Gynecol. and 0bst., 1911, March, 227 .

NOVARO, NICOLA, “ Su Pappendice ileo-caecale a sede intramesenterica ”, Gaz. d. 0.91)., 1921, xlii, 147.

REID, DOUGLAS G., “ Studies of the Intestine and Peritoneum in the Human Fcztus ”, Jaar. of Anat. and Ph_2/siol., 1911, xlv, 73, 406; “ Notes on the Folds of Perltoneum connected to the Appendix. and a. C3300-appendicular Fold ”, Jam-. of Anal. and Physiol., 1912, xlvi, 239; "‘ Notes on the Retrocolic Fossa, Splenic Process of Peritoneum, and Bloodless Fold of Treves”, Jour. of Anal. and Physiol., 1913, xlvii, 479.

ROBBINS, R. H., vide FRAZER, J. E .

TREVES, F., Hunterian Lectures, 1885, “The Anatomy of the Intestinal Canal and Peritoneum in Man ”, Brit. Med. Jaur., 1885.

TESTUT, L., Anatomic Ilumaine, 1905, iii.

WAKELEY, C. P. G., “ A Hundred and Twenty Cases of Acute Appendicitis treated by Operation ”. Lancet, 1919, ii.

Cite this page: Hill, M.A. (2024, June 25) Embryology Paper - The relative frequency of the various positions of the vermiform appendix (1924). Retrieved from

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