The human vermiform appendixA general surgeon’s reflectionsFirst published:TJ (now Journal of Creation) 3(1):31–38April 1988

by J. Warwick Glover

The Year 1986 Was

i. the 250th anniversary1 of the first successful removal of the appendix (appendectomy) and

ii. the 100th anniversary2 of the word ‘appendicitis’ (inflammation of the appendix) being used in the surgical literature.

The Disease

Acute appendicitis, although on the decline again, still looms large in the everyday life of a surgeon. It is still by far the commonest cause of a patient presenting with an acute abdomen. Although the results of treatment have improved dramatically in the past 75 years, generally reflecting the great advances surgery has made in that time, there is still a morbidity and mortality that cannot be considered insignificant.2,3,4 The present decline in incidence of the disease is possibly due to recent improvements in the previously deteriorating diet of Western civilisation (Rendle Short,5 Burkitt6).

The Organ—Macroscopic2,7,8,9,10

The appendix is commonly referred to as a classic example of a vestigial organ. Such a statement implies that the appendix represents a vestige of an organ with a former greater existence in the evolutionary sense, rather than in an earlier stage of its development.

It was because of Charles Darwin’s ‘Descent of Man’ (1871)11 in fact, that the vermiform caecal appendage became widely regarded as a rudimentary organ representing the much more developed distal caecum present (if evolution is assumed) in man’s more herbivorous ancestors.

Darwin’s Argument

Darwin’s argument about the appendix being vestigial was incorrect in his application of:

i. homology, and ii. Lamarckian inheritance.

Darwin and Homology

When he based his ideas concerning the organ’s function on homology, Darwin erred by:

a. regarding the caecum and appendix as part of the same unit organ, structurally and functionally, rather than (albeit in continuity) separate structures with different functions,

b. comparing the unit between different animal kinds, assuming similar functions of the complex, with emphasis on organ functioning being directly proportional to its size, and then

c. inferring the appendix is a rudiment in man on account of its small size and variability!

In thus making his comparison, he thus assumed evolution to explain the interpreted regression, but later argued that it was this regression that was later good evidence for evolution—a circular argument.

Darwin and Lamarckian Inheritance

Once Darwin erred in assuming that function declines with size, he erred further in assuming:

a. the mechanism for this decline was disuse, and that b. such an interpreted regression was inheritable, that is, successive generations acquire the

characteristic of a smaller and smaller caecum and appendix and transmit this characteristic to their offspring.

This type of inheritance, or should we say disinheritance, according to disuse is distinctively Lamarckian (even admitted by Ruse12 in his ‘Darwinism Defended’, p. 43) and such a mode of inheritance has long been discarded as it contradicts our basic understandings of Mendelian genetics.

Darwin’s Influence

After Darwin said the appendix was vestigial and useless, he and others went on to suggest it was more susceptible to disease. This propensity for the appendix to be diseased, and possibly dangerously so (‘Descent of Man’, p.27), is in no way due to the organ having a lowered vitality and tending towards an atrophic (wasted) defenceless state, but simply a consequence of one of its functions placing it in the body’s front-line in the battle against infection. Akin to the tonsil guarding the upper alimentary tract from bacteria etc., so does the appendix guard the entrance from the almost sterile ileum into the normally bacteria-infested colon (see Fig. 1).

Figure 1. Sketch of the human vermiform appendix and its location at the apex of the caecum below the entrance of the ileum.

Later still, Darwinists suggested the ready dispensability of the appendix proved its uselessness. This type of logic would have a daughter believing her mother’s womb was useless if her mother was unaffected after a hysterectomy in later life for a disease of the uterus.

The Organ -Microscopic2,7,8,9,13,14

Present day histology textbooks are starting to acknowledge that the appendix with its complicated and rich blood supply and marked tissue differentiation is a complex and highly specialised organ. Of course, the histological appearance of the appendix has been exactly the same all the time, but people are now starting to look at it from a different perspective.

The most recent edition of ‘Gray’s Anatomy’9 indicates in its embryology section that the appendix is a vestigial remnant indicative of man’s ancestors’ more herbivorous dietary habits, whereas the anatomical section says, ‘In view of its rich blood supply and histological differentiation, the vermiform appendix is probably more correctly regarded as a specialised than as a degenerate, vestigial structure. The configuration of the caecum and appendix in man and the anthropoid apes, is probably less primitive than in the monkeys.’9 Surely one can’t have it both ways!

From what has been said so far it can be seen that whereas in the past it was considered the appendix was becoming vestigial (involution with evolution), it is now generally accepted that

the appendix is a highly specialised, well-differentiated organ apparently developed to the maximum in its specialisation in man.

Comparative Mammalian Alimentary Tracts And Digestive Processes.2,7,10,15,16,17

A careful examination and comparison of aspects of digestion in several kinds of animal is now in order.

Rabbits

The rabbit gains amino acid nitrogen and other nutriments from the bacteria which digest the cellulose from grass etc. in its large caecum. The rabbit passes two types of stool; the one which is mucus-coated the rabbit eats (coprophagy), recycling it through the intestine to allow for absorption of the bacteriolytic products of grass digestion. Few animals would eat more grass than a rabbit, yet although it has a very large caecum acting as a fermentation tank, it also has a sizeable and distinctive appendix containing lymphoid aggregations in its wall.

Ruminants

With cleft hooves, the ruminants such as cows, sheep and goats have a four-chambered stomach and gain many of their nutriments from the bacteriolytic digestion of cellulose in the rumen chamber of their stomach after regurgitation many times to improve the mix-chewing the cud. The ruminant digestive mechanism also allows for some recycling of urea into the saliva for bacteria to utilise, as well as the bacteria converting the plant cell amino acids into its own type which are more akin to what the cow, for example, requires. These animals have a seizable caecum for additional bacterial fermentation to occur, but no appendix.

Horses

The horse has a more human-like stomach and gains nourishment by absorbing similar by-products of the bacteriolytic digestion of cellulose, as do most herbivores possessing such cellulase-producing bacteria in their gut. But the main absorption site of such products in the horse is through its very coiled and redundant caecum and colon. Once again the bacteria convert plant amino acids etc. to the preferred animal types. However, the horse does not have an appendix.

Dogs and Cats

Dogs and cats favour a mixed-to-carnivorous diet (or CAN-ivorous in domestication!) and obtain most of their nourishment from absorption of products of food digestion by their own small bowel juices, not unlike man. They have a bigger caecum than man where some bacterial fermentation occurs, but no appendix.

Monkeys

Whether so-called ‘New World’, or ‘Old World’, monkeys do not have an appendix. Eating more nutritious food, such as fruit and nuts, their digestion is aided to a greater degree by their own digestive juices, so that more absorption occurs higher in the alimentary canal. They have a caecum which is not terribly big, so it has been compared to the embryonic stage of the developing human caecum and appendix unit. But of course, if we were to follow this line of argument, we would have to say the appendix, rather than becoming rudimentary and disappearing, is appearing and developing as we ascend the supposed evolutionary scale. This raises other difficulties.

Anthropoid Apes and Man

The anthropoid apes (gibbon, orangutan, chimpanzee and gorilla) and man also have a small caecum but with a distinctive terminal appendix (see Fig. 1). Although they eat a mixed diet, they are predominantly herbivorous, but the bacteria in their caeca do not secrete cellulase. the necessary enzyme for cellulose degradation and digestion. Nourishment is mainly from the absorption of food breakdown-products resulting from their own digestive-juice actions in the small intestine not dissimilar from digestion and absorption which occurs in monkeys, cats and dogs.

Thus considering the digestive processes and absorption areas in several representatives of the animal kingdom, we see similarities and differences—mosaicism18,19 in the use of plan and purpose among animal kinds and discontinuity between animal kinds. The appendix, as a distinctive organ separate from the caecum, has been present and absent among the above examples.

Only A Few Diverse Mammals Possess An Appendix2,7,10,17

In a study of the alimentary tracts of animals we find the appendix is not present in any invertebrate. Among the vertebrates, it is absent in fish, amphibians, reptiles, birds and most mammals. In fact, the vermiform appendix, recognised as a worm-like, narrow extension beginning abruptly at the caecal apex (see Fig. 1 again) is only present in a few marsupials such as the wombat and South American opossum, a few rodents (rabbits and rats) and few primates (only the anthropoid apes and man). Note that monkeys do not have such an organ.2,7,10,17

Taking any evolutionary tree an evolutionist cares to suggest, and trying to correlate the appearance and disappearance of the appendix with such a tree, is impossible. A typical defence is either to argue that soft parts don’t fossilise and things must have been different in the past (evolutionists then ignoring their cherished axiom ‘The present is the key to the past’), or calling upon ‘convergent evolution’, which is a type of explain-anything phrase without mechanism that is frequently used to defy the above obvious type of mosaicism.

The Evolutionist Has A Mammoth Problem

If formerly the evolutionist had the appendix going and now has it coming, he cannot explain why it is first present in some marsupial animals like the wombat, but absent in all the mammals

between the wombat and apes and man, apart from the rabbit and a few rodents, and especially explaining the absence in monkeys.

Evolutionary postulations would have us believe that a tailed mammal without an appendix gave rise to a monkey with a tail but still without an appendix, which then gave rise to an ape without a tail but with an appendix, and then on to man where the appendix has developed to the extreme! Although an oversimplification, the above exemplifies the incredible problem the evolutionist now has with his supposedly vestigial appendix. With one argument he has us believing it’s going and with the other it’s coming. Perhaps it is neither going nor coming.

The Creationist Viewpoint

The fiat creationist would expect various kinds of animals to have alimentary tracts based on a common design, with modifications and specialisations on that basic blueprint being made in appropriate areas.19 Such alterations would still be according to plan and purpose, and conforming to the structural and functional needs of the organism in question in its natural environment. The organism would also have an inbuilt ability to adapt within a fixed range to allow for growth to maturity and adjustment to environmental variations. The caecum and appendix, when viewed as separate but related specialised entities in structure and function in the digestive tracts of different animal kinds, do not contradict creationist expectations.

Functions Of The Human Appendix2,4,7,8,20,21

The appendix completes most of its functions at the early end of the spectrum of life. The vital aspects of these are probably complete at least by early infancy. While it is freely admitted that the precise functions of the human vermiform appendix are still unclear, so much more is now known that clarification is at hand. It is my intention to discuss this further under the following headings:

1. Embryological 2. Physiological

3. Microbiological (Bacteriological)

4. Biochemical

5. Immunological

1. Embryological2,22

During the fifth foetal week it is the appendix which develops from a bud at the junction of the small and large bowel and undergoes rapid growth into a pouch. In the sixth week there is a transient nubbin surmounting the pouch indicative of being involved in the rapid development of the pouch which is very strategically placed near the apex of the highly significant mid-gut loop. It is only after the fifth foetal month that the proximal end of this pouch, which has appeared to

be a very insignificant structure up until this stage, starts growing differentially to give rise to the true caecum which continues to develop into infancy.

The embryonic appendix has finger-like projections (villi) on its inside surface and it is only around birth that the long ribbons (taeniae) causing the sacculation of the large bowel start to develop. These ribbons, of course, converge on the base of the appendix.

2. Physiological2,23,24,25

The goblet cells lining the appendix and adjacent caecum and colon secrete a special type of mucus which can be regarded as an antibacterial paint controlling the organisms which develop in the bowel in the region. The paint contains a high concentration of IgA type immunoglobulins, secretory antibodies produced for mucosal or surface immunity and part of the bowel-blood barrier .

3. Bacteriological2,23,24,25

Through the cells within and overlying the lymphoid follicles and their production of secretory and humoral antibodies the appendix would be involved in the control of which essential bacteria come to reside in the caecum and colon in neonatal life. As well it would be involved in the development of systemic tolerance to certain antigenic agents within the alimentary tract whether they are derived from bacteria, foodstuffs or even the body’s own proteolytic enzymes.

4. Biochemical2

One in three hundred or so appendectomy specimens contains a carcinoid tumour composed of a highly specialised type of cell rich in vaso-active peptides such as serotonin. The exact function of such agents in the entire bowel is still being elucidated, but the fact that the majority4 of such tumours occur within the appendix is indicative that the appendix could well be involved in some way with such substances.

5. Immunological2,4,9, 13,14,20,2.1,23,25,26,27,28,29

This is the area where the appendix would seem to have its predominant functions due to its content of lymphoid follicles, which are highly specialised structures. Although it was thought the appendix itself could be the site for B-lymphocyte induction (a Bursa of Fabricius equivalent)26 the latest opinions favour this programming being more centralised in the bone marrow. The appendix may still have a role in this highly significant function, but not alone, and its lymphoid tissue is known for certain to be involved in antibody production (the function of B- type lymphocytes). These antibodies are of two types:

i. IgA type immunoglobulins for secretory or mucosal surface immunity, and ii. IgM and IgG immunoglobulins for humoral or bloodstream immunity.

The above type functions have proven the appendix to be part of the G.A.L.T.2,4,23,25 (Gut Associated Lymphoid Tissue), but it has also been shown that the appendix after the neonatal

period is dispensable, meaning that normal G.A.L.T. functions remain after appendectomy. This result is not unexpected as similar lymphoid tissue is distributed up and down the alimentary tract, there being a considerable reserve potential. Experiments in rabbits have shown that the appendix alone can provide normal humoral antibody levels if necessary27 and also replenish depleted lymphocyte populations secondary to neonatal thymectomy.28

These results have been in rabbits, and the rabbit appendix is not exactly the same as the human. Studies of the functions of the human appendix, however, have tended to concentrate on extrapolating across from animal models where it is difficult to escape evolutionary overtones and possibly repeating the errors Darwin made when using homology.

Other studies on the human appendix have tended to concentrate on tissue from young adults when the appendix has probably completed its major role. Recently the topography14 of immune cells and their products in the appendix have been described both in the presence and absence of acute inflammation, as well as it becoming evident that lymphocytes individually move into the appendix between the tenth and twentieth foetal week.14 Such studies have also highlighted the mode of immune cell reactions both with each other and other cells in the area in a detail not known before and quite significant advances have been made. Of course, lymphoid follicles do not actually appear as such in the appendix until two weeks after birth4 at the same time that colonisation of the large bowel with bacteria which are safe to their host begins. The follicles increase steadily in number to a maximum of two hundred at about fifteen to twenty years of age and decline back to about one hundred by thirty years of age and decline further, even to disappearance, throughout the rest of life. The peak incidence of acute appendicitis coincides very well with the peak number of lymphoid follicles and their enlargement with infection, whether it be initially viral or bacterial, probably contributes significantly to the luminal obstruction29 so important in the initiation of acute appendicitis.

In the past decade we have increased our knowledge considerably of the cells lining the gastrointestinal tract, especially in the small bowel and ileocaecal region, where new hormones and their functions have been discovered and so have received a lot of attention in appropriate journals. Clarification of B-lymphocyte induction9,13,26 and topography of the cells in foetal and neonatal appendiceal tissues is awaited with interest.

In summary therefore, the human vermiform appendix appears to be a complex and organised structure both in its development and maturation, and almost certainly has corresponding complexity in its functions which, like most gastrointestinal functions, are still awaiting further clarification. It would appear that the functions of the appendix would be most important when the organ itself has most prominence, and this is in the developing foetus and early existence after birth. The inside of the bowel is outside the body and the area where substances foreign to it have their greatest chance of attack. The appendix appears to be strategically placed and structurally composed of tissues which are vital in establishing and maintaining the various types of body defences or immunity necessary in recognition of such assaults and having a part to play in their repulsion. The appendix is thus one of the guardians of the internal environment of the body from the hostile external environment.

Conclusions

The vermiform appendix occurs only in a few diverse mammals.10 This supports the view that among animal kinds with respect to the occurrence of such a particular and specialised feature one sees mosaicism in its distribution with discontinuity between animal kinds. A careful assessment of the embryology of the appendix in humans indicates that quantitatively it has a very early and rapid development during the critical stages of bowel growth and organisation. However, microscopically the tissues of the appendix are complicated and highly specialised, but this qualitative aspect of the organ’s growth does not occur until just after birth when the neonate takes on essential bacteria to reside in its colon.

The appendix would appear to have a role (although not as the sole organ) in establishing and maintaining the bowel-blood barrier for such bacteria in its area. The special aspects of the mucus produced in this area (the antibacterial paint-like action) along with the appendix figuring in the development of its region have been discussed. It has also been shown that the appendix can in no way be vestigial in an evolutionary sense. The hallmarks of the appendix thus appear to be creative design and organisation as if it is formed according to a plan to play a specific purpose. If one studies any organ or organism in the living world, one comes across such a discontinuous and mosaic distribution of structural and functional features among animal kinds. The features for structure and function go hand in glove with each other, obeying sound principles of design engineering and organisation yet possessing incredible functional capacities. Notwithstanding such features, there is also an economy of effort to achieve them and within the system an inherent beauty. Such studies speak of an all-wise Great Architect having dominion over His every creation, be it big or small, fat or thin, so that no one can deny we are ‘fearfully and wonderfully made’.

Recommended Resources

References

1. Williams, G.R., 1983. A history of appendicitis. Ann. Surg., 197:495f. 2. Glover, J.W., 1984. The appendix revisited. Proceedings of the Provincial Surgeons of

Australia 20th A.G.M., pp.1-5.

3. Maingot, R., 1974. Abdominal Operations, Appleton-Century- Crofts, 6th edition, Vol. 2, p. 1350f.

4. Schwartz, S., 1984. Principles of Surgery, McGraw-Hill, fourth edition, p.1245f.

5. Rendle Short, A., 1920. Br. J. Surg., 8:171f. (Arthur Rendle- Short, 1880-1953, was the father of the present chairman of Creation Science Foundation, Professor John Rendle-Short. He wrote on appendicitis and diet in this classic 1920 paper.)

6. Burkitt, D.P., 1971. The aetiology of appendicitis. Br. J. Surg., 58:695f.

7. Kelly, H.A. and Hurdon, E., 1905. The Vermiform Appendix and Its Diseases, W. B. Saunders, Philadelphia.

8. Robbins, S.L. and Cotran, R.S., 1979. Textbook of Pathology. Saunders, second edition.

9. Williams, P.L. and Warwick, R., 1980. Gray’s Anatomy, Churchill Livingstone, 36th edition.

10. Berry, R.J.A., 1900. The true caecal apex, or the vermiform appendix: Its minute and comparative anatomy. J. of Anat. and Physiol., 35:83f.

11. Darwin, C., 1871. The Descent of Man, J. Murray, London; esp. pp.17-33.

12. Ruse, M., 1982. Darwinism Defended, Addison-Wesley.

13. Wheater, P.R., Burkitt, H.G. and Daniels, V.G., 1982. Functional Histology: A Text and Colour Atlas, Churchill Livingstone. ELBS edition.

14. Tome, V.A. and Retief, F.P., 1978. Human vermiform appendix, Immunocompetent cell topography and cell to cell interactions in situ. J. of Immunolog. Methods, 20:333f.

15. Wilson, E.O., Eisner, T., Briggs, W.R., Dickerson, R.E., Metzenberg, R.L., O.Brien. R.D., Susman, M. and Boggs, W.E., 1978. Life on Earth -Biology Text, second edition.

16. Curtis. H., 1984. Biology, Worth, fourth edition.

17. Kavanagh, M., 1983. A Complete Guide to Monkeys, Apes and Other Primates, Cape.

18. Denton, M., 1985. Evolution: A Theory in Crisis, Burnett, London.

19. Parker, G., 1980. Creation: Facts of Life, Creation-Life Publishers, San Diego.

20. Sleisenger. M.H. and Fordtran. J.S.. 1983. Gastrointestinal Disease. Saunders, third edition, p.1268f.

21. Way, L.W., 1985. Current Surgical Diagnosis and Treatment, Lange. seventh edition.

22. England. M.A.. 1983. A Colour Atlas of Life Before Birth. Wolfe Med.

23. Chadwick. V.S. and Phillips. S., 1982. Small Intestine B.I.M.R. Gastroenterology 2. Butterworth.

24. Alexander-Williams. I. and Binder. H.I., 1983. Large Intestine B.I.M.R. Gastroenterology 3. Butterworth.

25. Doe. W., 1986. Immunology of the gastrointestinal tract. Medicine International. 2:1044f.

26. Perey. D. Y., Cooper. M.D. and Good. R.A.. 1968. The mammalian homologue of the avian Bursa of Fabricius. Surgery, 64:614f.

27. Sussdorf. D.M. and Draper. L.R.. 1956. Antibodies in rabbits after irradiation; shielding the appendix. J. of Infect. Dis., 99:129f.

28. Archer. O.K.. Sutherland. D.R. and Good. R.A.. 1963. The appendix in rabbits after neonatal thymectomy. Nature. 200:337f.

29. Wangensteen. O.H. and Dennis. C.. 1939. Experimental proof of the obstructive origin of appendicitis in man. Ann. Sorg., 110:629.

The Appendix—An Addition on the Appendix

The Latin word ‘addendum’ means an addition.

The Latin word ‘appendix, appendicis f.’ means an appendage -an addition at the end (of a book for example), being an addition almost as an afterthought and not regarded as of great value to the overall theme of the topic at hand. Thus whereas the choice of the adjective ‘vermiform’, meaning worm-like, is accurately descriptive of the organ, the choice of the noun ‘appendix’ from the beginning of the organ’s nomenclature, gave it little chance of ever being considered important.

In an excellent review article on ‘A History of Appendicitis’, in a presidential address to the 94th meeting of the Southern Surgical Association, G. Rainey Williams, of the University of Oklahoma Department of Surgery, pointed out that the reason the appendix is not mentioned in very early anatomical studies is probably because the studies were done on animals not possessing an appendix.’ Perusing the above and other excellent review articles on the history of the appendix (Kelly and Hurdon,2 Shepherd,3 Seal4 and Maingot5) allows one to outline the highlights of such a history:

1492 Leonardo da Vinci clearly depicted the organ in his anatomical drawings.

1521 Berengario DaCarpi first described the organ.

1530 Vido Vidius first named the worm-like organ as the vermiform appendix.

1543 Andreas Vesalius had it well illustrated in ‘De Humani Corporis Fabrica.’

1711Lorenz Heister gave the first good description of a case of acute appendicitis—a post mortem on an executed criminal.

1735Claudius Amyand performed the first recorded successful appendicectomy -the appendix, perforated by a pin, and surrounding omentum were removed through a scrotal wound while dealing with a faecal fistula in a chronic hernia in an 11-year-old boy.

1767 John Hunter described a gangrenous appendix at post mortem.

1812 John Parkinson first described a faecolith in a perforated appendix at post mortem.

1827Francois Melier suggested the possibility of appendicectomy as an operation. Dupuytren opposed this view.

1839Bright and Addison published a medical textbook clearly outlining the symptomatology of acute appendicitis. Hodgkin agreed.

1850sonwards—anaesthesia took off, perityphlitis abscesses drained —Hancock (1848), Willard Parker (1867) and others (1870s)

1867 Joseph Lister gave his first paper on ‘Antisepsis’.

1880Lawson Tait operated with the express intent of performing appendicectomy having made a pre-operative diagnosis of disease of the organ.

1883 Abraham Groves of Ontario did likewise.

1884Mikulicz in Krakow recommended and performed surgery for appendicitis. Kronlein in Germany did likewise.

1885Charter Symonds, an Englishman, performed the first interval operation for appendicitis but did not remove the appendix.

1886Hall of New York in May performed appendicectomy but had not commenced the operation with such an intent.

1887

Sir Frederick Treves of London unkinked an appendix in February of that year. Morton, seven years after Tait in England and four years after Groves in Canada, in April of that year performed the first deliberated appendicectomy for appendicitis in the United States. Treves recommended interval appendicectomy in September of that year. Sands in December of that year removed an appendix, thus following what he had been preaching for some time.

1888onwards for a decade brought improvement of technique -Treves, Senn, McBurney, Weir, Worcester, Fowler, Deaver, Marcy and Richardson.

1886

When —June 18, 1886, at the first meeting of the Association of American Physicians.Where—in Washington DC.With the likes of Sternberg, Welch and Osler.What—the first good description of perityphlitis and iliac passion was given.By—Reginald Heber Fitz who was Shattuck Professor of Pathological Anatomy at Harvard University. R.H. Fitz read a paper entitled ‘Perforating Inflammation on the Vermiform Appendix with Special Reference to its Early Diagnosis and Treatment’. He had been a pupil of Virchow, and being a pathologist gave a detailed description of the pathology of the condition. He used the term ‘acute appendicitis’ which mixes a Latin root ‘appendix, appendicis f.’ and the Greek suffix ‘-itis’ implying inflammation and recommended early surgery removal as treatment. He is also noted for a very good paper in 1889 on ‘Pancreatitis’.

1894June -McArthur was to speak on a muscle- splitting incision but the meeting went over time and he did not present his paper. July -McBurney outlined the grid-iron incision and named his ‘point’.

1902Oschner and Sherren suggested a conservative regime to prevent infection spreading making subsequent surgery safer.

1904Murphy reported 2.000 appendicectomies between 1880 and 1903 mostly being what we call interval appendicectomies and named his triad (pain, vomiting and R.I.F. tenderness).

1905 Rockey described a transverse skin incision which Elliot had done in 1896.

1906 Davis, Harrington, Weir and Fowler all wrote on appendicectomy and incisions.

Among famous American surgeons of the time, Ephraim McDowell died of the disease, as did Fowler, whereas Wangensteen survived. Walter Reid died of the disease. Harvey Gushing, the father of modern neurosurgery, survived and Halsted was his surgeon.

Sir Frederick Treves was ‘The Elephant Man’s surgeon.

In 1902 he operated on Edward VII for an acute appendicitis with abscess the very day before the King (as successor to his mother Queen Victoria, who died in 1901) was to have his coronation. The coronation, of course, had to be postponed.

Treves performed the first unkinking of the appendix operation (1887) and in England and Europe was known as a proponent for interval appendicectomy (also 1887). He described the bloodless fold as part of the mesentery of the appendix, wrote on the positions or the appendix around the caecal apex according to a clock race, and also wrote on the types or caecum to which the appendix was attached. His own daughter died of acute appendicitis.

References

1. Williams. G.R., 1983. A history or appendicitis. Ann. Surg., 197:495f. 2. Kelly. H.A. and Hurdon. E., 1905. The Vermiform Appendix and Its Diseases. W.B.

Saunders, Philadelphia.

3. Shepherd. J.A., 1960. Surgery of the Acute Abdomen. E. & S. Livingston Ltd. p.401f.

4. Seal. A., 1981. Appendicitis: a historical review. Canadian J. of Surg., 24(4):427f.

5. Maingol. R., 1974. Abdominal Operations. Applelon-Century- Crofts, 6th edition. Vol.2., p.1370 f.

The vestigiality of the human vermiform appendix

A modern reappraisal

Copyright © 2003-2007 by Douglas Theobald, Ph.D. [Last Update: April 19, 2007]

"The vermiform appendage—in which some recent medical writers have vainly endeavoured to find a utility—is the shrunken remainder of a large and normal intestine of a remote ancestor. This interpretation of it would stand even if it were found to have a certain use in the human body. Vestigial organs are sometimes pressed into a secondary use when their original function has been lost."

Joseph McCabe The Story of Evolution (1912), p. 264

"Its major importance would appear to be financial support of the surgical profession."

Alfred Sherwood Romer and Thomas S. Parsons The Vertebrate Body (1986) , p. 389.

Other Links: "Your appendix: It's there for a reason", by Ken Ham and Carl Wieland

An overstated view from the most influential creationist organization on the function and purpose of the human appendix.

"The Human Vermiform Appendix – a General Surgeon's Reflections", by J. Warwick Glover, M.D.

An anti-evolutionist and special-creationist doctor speaks on the possible functions of the appendix.

Outline

Introduction The vermiform appendix: background information

The caecum

The caecal apex and the appendix are homologous

Intermediates between the caecum and the appendix

Possible functions of the appendix

The appendix is a suboptimal design

Evolutionary misconceptions in the medical literature

How to disprove that the appendix is a vestige

Conclusion

Acknowledgements

References

Introduction

Many biological structures can be considered vestiges given our current evolutionary knowledge of comparative anatomy and phylogenetics. In evolutionary discussions the human vermiform appendix is one of the most commonly cited vestigial structures, and one of the most disputed. Evolutionary vestiges are, technically, any diminished structure that previously had a greater physiological significance in an ancestor than at present. Independently of evolutionary theory, a vestige can also be defined typologically as a reduced and rudimentary structure compared to the same homologous structure in other organisms, as one that lacks the complex functions usually found for that structure in other organisms (see, e.g. Geoffroy 1798).

Classic examples of vestiges are the wings of the ostrich and the eyes of blind cavefish. These vestigial structures may have functions of some sort. Nevertheless, what matters is that rudimentary ostrich wings are useless as normal flying wings, and that rudimentary cavefish eyes are useless as normal sighted eyes. Vestiges can be functional, and speculative arguments against vestiges based upon their possible functions completely miss the point.

For more discussion of the vestigial concept, extensive modern and historical references concerning its definition (especially the allowance for functionality), see the Citing Scadding (1981) and Misunderstanding Vestigiality and 29+ Evidences for Macroevolution: Anatomical vestiges FAQs.

The following discussion makes four main points:

1. The human appendix may have bona fide functions, but this is currently controversial, undemonstrated in humans, and irrelevant as to whether the appendix is a true vestige or not.

2. The appendix is a prime example of dysteleology (i.e. suboptimal structural design), a prediction of genetically gradual evolution.

3. The appendix is a rudimentary tip of the caecum and is useless as a normal, cellulose-digesting caecum.

4. Thus, the appendix is vestigial by both the evolutionary and non-evolutionary, typological definitions of vestigiality.

The vermiform appendix: background info

Figure 1: The human vermiform appendix (image reproduced with modifications from Gray 1918)

In humans, the vermiform appendix is a small, finger-sized structure, found at the end of our small caecum and located near the beginning of the large intestine (Fawcett and Raviola 1994, p. 636; Oxford Companion to the Body 2001, pp. 42-43; Williams and Myers 1994). The adjective "vermiform" literally means "worm-like" and reflects the narrow, elongated shape of this intestinal appendage. The appendix is typically between two and eight inches long, but its length can vary from less than an inch (when present) to over a foot. The appendix is longest in childhood and gradually shrinks throughout adult life. The wall of the appendix is composed of all layers typical of the intestine, but it is thickened and contains a concentration of lymphoid tissue. Similar to the tonsils, the lymphatic tissue in the appendix is typically in a constant state of chronic inflammation, and it is generally difficult to tell the difference between pathological disease and the "normal" condition (Fawcett and Raviola 1994, p. 636). The internal diameter of the appendix, when open, has been compared to the size of a matchstick. The small opening to the appendix eventually closes in most people by middle age. A vermiform appendix is not unique to humans. It is found in all the hominoid apes, including humans, chimpanzees, gorillas, orangutans, and gibbons, and it exists to varying degrees in several species of New World and Old World monkeys (Fisher 2000; Hill 1974; Scott 1980).

The caecum: a specialized herbivorous organ

Our appendix is a developmental derivative and evolutionary vestige of the end of the much larger herbivorous caecum found in our primate ancestors (Condon and Telford 1991; Williams and Myers 1994, p. 9). The word "caecum" actually means "blind" in Latin, reflecting the fact that the bottom of the caecum is a blind pouch (a dead-end or cul-de-sac).

In most vertebrates, the caecum is a large, complex gastrointestinal organ, enriched in mucosal lymphatic tissue (Berry 1900), and specialized for digestion of plants (see Figure 2; Kardong 2002, pp. 510-515). The caecum varies in size among species, but in general the size of the caecum is proportional to the amount of plant matter in a given organism's diet. It is largest in obligate herbivores, animals whose diets consist entirely of plant matter. In many herbivorous mammals the caecum is as large as the rest of the intestines, and it may even be coiled and longer than the length of the entire organism (as in the koala). In herbivorous mammals, the caecum is essential for digestion of cellulose, a common plant molecule. The caecum houses specialized, symbiotic bacteria that secrete cellulase, an enzyme that digests cellulose. Otherwise cellulose is impossible for mammals to digest.

The structure of the caecum is specialized to increase the efficiency of cellulose fermentation. As a "side branch" from the gut it is able to house a large, dense, and permanent colony of specialized bacteria. Being a dead-end sac at the beginning of the large intestine, it allows more time for digesting food to reside in the gut and ferment more completely, before passing through the large intestine where the resulting nutrients are absorbed. However, even though humans are herbivorous, the small human caecum does not house significant quantities of cellulase-excreting bacteria, and we cannot digest more than but a few grams of cellulose per day (Slavin, Brower, and Marlett 1980).

Figure 2: Gastrointestinal tracts of various mammals. For each species, the stomach is shown at top, the small intestine at left, the caecum and associated appendix (if present) in magenta, and the large intestine at bottom right. Scale

differs between species. Reproduced with modifications from Kardong 2002, p. 511. Copyright © 2002 McGraw-Hill.

The human appendix is homologous to the end of the mammalian caecum

In vertebrate comparative anatomy, it has long been known that the human appendix and the end of the mammalian caecum are structurally homologous (Berry 1900; Fisher 2000; Hill 1974; Hyman 1979, p. 412; Kardong 2002, pp. 513-515; Kluge 1977, p. 1977; Neal and Rand 1936, p. 315; Romer and Parsons 1986, p. 389; Royster 1927, p. 27; Smith 1960, p. 305; Weichert 1967, p. 189; Wiedersheim 1886, p. 236; Wolff 1991, p. 384). Of course, the end of the caecum and the appendix can be homologous and have different functions. Being the termination of the caecum, the human vermiform appendix is also a "blind pouch," and another name for the appendix is in fact the "true caecal apex" (Berry 1900). Within the gastrointestinal tract of many vertebrates, mammals, and primates in particular, the termination of the caecum and the vermiform appendix share the same relative position (Figure 2), both have a similar structure and form, both are blind sacs enriched with lymphatic tissue (Berry 1900), both have a common developmental origin (Condon and Telford 1991; Williams and Myers 1994, p. 9), and, as discussed below, in the primates both are connected by an extensive series of intermediates. These observations firmly

establish these structures as homologous by standard systematic criteria (Kitching et al. 1998, pp. 26-27; Remane 1952; Schuh 2000, pp. 63-64; Rieppel 1988, p. 202), a conclusion confirmed by cladistic systematic analysis (Goodman et al. 1998; Shoshani 1996).

A few other mammals appear to have a structure similar to the hominoid vermiform appendix, including the wombat, South American opossum (both marsupials), some rodents, and the rabbit. However, extensive comparative analysis has shown that the caecal appendixes of humans and these other mammals were derived from the caecum independently; these structures are not homologous as appendixes (Shoshani and McKenna 1998). The relationship between these other caecal structures and the hominoid vermiform appendix is similar to the homology of bat and bird wings. The wings of bats and birds are homologous as modified forelimbs, yet they are not homologous as wings. Likewise, the appendixes of rabbits and humans are homologous as modified caeca, yet they are not homologous as appendixes. If the rabbit and human appendix have similar functions (which has never been experimentally demonstrated), they are the result of independent convergence of function and form (Shoshani and McKenna 1998). The many significant morphological, histological, and cellular differences between the rabbit and human appendixes (discussed below) all are consistent with a superficial convergent relationship.

Structural intermediates of the appendix and caecum in primate phylogeny

The primate family tree provides a rather complete set of intermediates between the states "large caecum/appendix absent" to "small caecum/appendix present". Many primates have both a caecum and an appendix, or a structure intermediate between the two. The anatomical definition of a vermiform appendix is a narrowed, thickened, lymphoid-rich caecal apex (Fisher 2000 and references therein). As already mentioned, the hominoid apes all bear a vermiform appendix, but many non-anthropoid primates also have structures that fit the above definition to varying degrees. In fact, recent reevaluation of the anatomy of the primate caecum and appendix has highlighted the difficulties in determining exactly where the caecum ends and the appendix begins in different species (Fisher 2000). This complication arises from the continuous, variable, and overlapping nature of caecal and appendicular tissues, both histologically and anatomically. For example, in most primates the caecal apex is rich in lymphoid tissue and is thickened, but whether it is narrowed into a conical or "worm-like" structure is variable (Fisher 2000).

From systematic analysis of comparative anatomy, it is known that in primates a large caecum with a small or absent appendix is the ancestral, primitive state (Goodman et al. 1998; Shoshani 1996). In general, the length of the caecum, relative to that of the colon, decreases as one traverses the primate phylogenetic tree from monkeys to humans. Concurrently, the size of the appendix increases. The appendix is mostly absent in prosimians and New World monkeys, yet they have a large caecum. In Old World monkeys the appendix is more recognizable, and it is well-developed in the anthropoid apes, which lack the large cellulose-fermenting caecum found in their ancestors and other primates (Fisher 2000; Goodman et al. 1998; Hill 1974; Shoshani 1996; Scott 1980).

Possible function of the appendix

"The appendix n, of the colon n m, is a part of the caecum and is capable of contracting and dilating so that excessive wind does not rupture the caecum."

Leonardo da Vinci FB 14v (1504-1506). from O'Mally and Saunders 1952, Leonardo da Vinci on the human body, p. 185.

Earliest known drawing of the appendix,

by Leonardo da Vinci.

Throughout medical history many possible functions for the appendix have been offered, examined, and refuted, including exocrine, endocrine, and neuromuscular functions (Williams and Myers 1994, pp. 28-29). Today, a growing consensus of medical specialists holds that the most likely candidate for the function of the human appendix is as a part of the gastrointestinal immune system. Several reasonable arguments exist for suspecting that the appendix may have a function in immunity. Like the rest of the caecum in humans and other primates, the appendix is highly vascular, is lymphoid-rich, and produces immune system cells normally involved with the gut-associated lymphoid tissue (GALT) (Fisher 2000; Nagler-Anderson 2001; Neiburger et al. 1976; Somekh et al. 2000; Spencer et al. 1985). Animal models, such as the rabbit and mouse, indicate that the appendix is involved in mammalian mucosal immune function, particularly the B and T lymphocyte immune response (Craig and Cebra 1975). Animal studies provide limited evidence that the appendix may function in proper development of the immune system in young juveniles (Dasso and Howell 1997; Dasso et al. 2000; Pospisil and Mage 1998).

However, contrary to what one is apt to read in anti-evolutionary literature, there is currently no evidence demonstrating that the appendix, as a separate organ, has a specific immune function in humans (Judge and Lichtenstein 2001; Dasso et al. 2000; Williams and Myers 1994, pp. 5, 26-29). To date, all experimental studies of the function of an appendix (other than routine human appendectomies) have been exclusively in rabbits and, to a lesser extent, rodents. Currently it is unclear whether the lymphoid tissue in the human appendix performs any specialized function apart from the much larger amount of lymphatic tissue already distributed throughout the gut. Most importantly with regard to vestigiality, there is no evidence from any mammal suggesting that the hominoid vermiform appendix performs functions above and beyond those of the lymphoid-rich caeca of other primates and mammals that lack distinct appendixes.

As mentioned above, important differences exist in nearly all respects between the human and rabbit appendixes (Dasso et al. 2000; Williams and Myers 1994, p. 57). The rabbit appendix, for instance, is very difficult to identify as separate from the rest of its voluminous caecum (see Figure 2). Unlike the human appendix, the rabbit's appendix is extremely large, relative to the colon, and is the seat of extensive cellulose degradation due to a specialized microflora. The large rabbit appendix houses half of its GALT lymphoid tissue, whereas the contribution of the human appendix to GALT is significantly less (Dasso et al. 2000). In humans the vast majority of GALT tissue is found in hundreds of Peyer's patches coating the small intestine and in nearly 10,000 similar patches found in the large intestine. Additionally, there are important differences in lymphoid follicular structure, in T-cell distribution, and in immunoglobulin density (Dasso et al. 2000). Furthermore, from systematic analysis we know that the rabbit, rodent, and human

appendixes are convergent as outgrowths and constrictions of the caecum (Shoshani and McKenna 1998). It is thus very questionable to conclude from these animal studies that the human appendix has the same function as the other non-primate appendixes.

Of course, over a century of medical evidence has firmly shown that the removal of the human appendix after infancy has no obvious ill effects (apart from surgical complications, Williams and Myers 1994). Earlier reports of an association between appendectomy and certain types of cancer were artifactual (Andersen and Isager 1978; Gledovic and Radovanovic 1991; Mellemkjaer et al. 1998). In fact, congenital absence of the appendix also appears to have no discernable effect. From investigative laparoscopies for suspected appendicitis, many people have been found who completely lack an appendix from birth, apparently without any physiological detriment (Anyanwu 1994; Chevre et al. 2000; Collins 1955; Hei 2003; Host et al. 1972; Iuchtman 1993; Kalyshev et al. 1995; Manoil 1957; Pester 1965; Piquet et al. 1986; Ponomarenko and Novikova 1978; Rolff et al. 1992; Saave 1955; Shperber 1983; Tilson and Touloukian 1972; Williams and Myers 1994, p. 22).

In sum, an enormous amount of medical research has centered on the human appendix, but to date the specific function of the appendix, if any, is still unclear and controversial in human physiology (Williams and Myers 1994, pp. 5, 26-29).

The appendix is suboptimally designed

The human appendix is notorious for the life-threatening complications it can cause. Deadly infection of the appendix at a young age is common, and the lifetime risk of acute appendicitis is 7% (Addiss et al. 1990; Hardin 1999; Korner et al. 1997; Pieper and Kager 1982). The most common age for acute appendicitis is in prepubescent children, between 8 and 13 years of age. Before modern 20th-century surgical techniques were available, a case of acute appendicitis was usually fatal. Even today, appendicitis fatalities are significant (Blomqvist et al. 2001; Luckmann 1989).

The small entrance to this dead-end pocket makes the appendix difficult to clean out and prone to physical blockage, which ultimately is the cause of appendicitis (Liu and McFadden 1997). This peculiar structural layout is quite beneficial for a larger cellulose-fermenting caecum, but it is unclear why gut lymphoid tissue would need to be housed in a remote, dead-end tube with negligible surface area. In fact, 60% of appendicitis cases are due to lymphoid hyperplasia leading to occlusion of the interior of the appendix, indicating that the appendix is unusually prone to abnormal proliferation of its lymphoid tissue (Liu and McFadden 1997). Such an occurrence would be much less problematic if the interior of the appendix were not so small, confined, and inaccessible from the rest of the gut. In many other primates and mammals, the GALT lymphoid tissue appears to function without difficulty in a much more open, bulbous caecum with ample surface area.

Furthermore, there is mounting evidence that removing the appendix helps prevent ulcerative colitis, a nasty inflammatory disease of the colon (Andersson et al. 2001; Buergel et al. 2002; Judge and Lichtenstein 2001; Koutroubakis and Vlachonikolis 2000; Koutroubakis et al. 2002; Naganuma 2001; Rutgeerts 1994). This evidence suggests that the appendix is actually

maladaptive, and that the lymphoid tissue contained in the appendix is prone to chronic pathological inflammatory states. If the appendix does have an important function that we have yet to find, it is a leading candidate for the worst designed organ in the human body. How nice if the appendix would just degenerate away after it is no longer needed, so it could never get infected and kill us needlessly. Any biological structure that supposedly ensures our livelihood by its functions, yet paradoxically and unnecessarily kills a large fraction of its bearers prematurely, is poorly designed indeed.

Why do some medical sources question the vestigiality of the appendix?

The reasons for this are multiple, but they largely stem from the simple fact that most physicians are not trained in evolutionary biology. The erroneous "completely nonfunctional" definition of a vestige is primarily found in medical papers, textbooks, and dictionaries (e.g. Williams and Myers 1994, p. ix). Using this incorrect and nonevolutionary definition, it is logical to conclude that a structure is not vestigial if its function is discovered. For instance, based upon this incorrect definition, Williams and Myers 1994 incorrectly argue that an evolutionary vestige cannot be both a complex and a "regressive" structure (p. 27). Similarly, a modern version of Gray's Anatomy confusingly implies that the appendix cannot be both vestigial and specialized (Williams and Warwick 1980). However, vestiges are very often complex or specialized structures, in fact overly complex for their functions, and prime examples are the wing of the ostrich and the eyes of blind cavefish. A vestige can be a complex structure, in an absolute sense, while simultaneously being rudimentary or degenerate relative to the same homologous structure in other organisms.

Perhaps most important is the fact that a vestige can be identified only via comparative analysis. Physicians are experts on human anatomy and physiology, but rarely do discussions in medical publications consider phylogenetic and comparative issues. Medical articles that attempt to consider phylogenetics often provide a gross misconception of evolutionary fundamentals. For instance, the most thorough and in depth source on the physiology of the human appendix, Williams and Myers 1994, refers to how the appendix changes as "the primate scale is ascended" and to the "evolutionary scale" with humans at its end (pp. 26-27). These are long-refuted orthogenetic concepts which have been contradicted by basic evolutionary theory since Darwin. Scott 1980 similarly argues against vestigiality based upon orthogenetic concepts and a belief in evolutionary "progress." Fisher 2000 (p. 229) and Scott 1980 both incorrectly imply that a vestige cannot be a derived character, a curious assessment since a vestige must be a phylogenetically derived character by definition.

How would we know if the appendix were not vestigial?

Whether the appendix has a function of some sort or not has no direct bearing on whether it is a bona fide vestige. However, at least three possible observations would help negate the conclusion that the human appendix is vestigial, using either the evolutionary or the typological definitions of vestigiality:

(1) if the human appendix were actually as large and developed as, say, the caecum of a prosimian or New World monkey;

(2) if the human appendix contributed significantly to cellulose fermentation and contained a large amount of cellulose-digesting bacteria;

(3) if we could demonstrate via phylogenetic or systematic methods that the apex of the cellulose-fermenting caecum in other primates and the vermiform appendix were not structurally homologous as side branches from the intestine.

An additional possible observation would contradict the conclusion of vestigiality by the evolutionary definition:

(4) if phylogenetic methods indicated that no predicted ancestors of humans ever had a large, cellulose-fermenting caecum (i.e., that a large, cellulose-digesting caecum is actually a derived primate character, not a primitive one).

All four of these potential observations are demonstrably false. Additionally, each is based upon positive scientific evidence: (1) we can measure and quantitate the size of the appendix; (2) we can measure and quantitate the amount of cellulose digestion occurring in the appendix; (3) we can observe and compare the relative positions, underlying structures, forms, and development of the organs in the gastrointestinal tracts of various organisms; and (4) we can determine primitive and derived characters by independent phylogenetic analysis. Therefore, the conclusion of vestigiality is susceptible and open to scientific testing against empirical observation. As such the concept of vestigiality is not an "argument from ignorance." It is clearly scientific in nature, based completely upon positive evidence.

Conclusion: The vermiform appendix is vestigial

Currently, arguments against the vestigiality of the human vermiform appendix have been based upon misunderstandings of what constitutes a vestige and of how vestiges are identified.

From an evolutionary perspective, the human appendix is a derivative of the end of the phylogenetically primitive herbivorous caecum found in our primate ancestors (Goodman et al. 1998; Shoshani 1996). The human appendix has lost a major and previously essential function, namely cellulose digestion. Though during primate evolution it has decreased in size to a mere rudiment, the appendix retains a structure that was originally specifically adapted for housing bacteria and extending the time course of digestion. For these reasons the human vermiform appendix is vestigial, regardless of whether or not the human appendix functions in the development of the immune system.

From a nonevolutionary, typological perspective, the human appendix is homologous to the end of the physiologically important, large, cellulose-fermenting caeca of other mammals. Even though humans eat cellulose, the contribution to cellulose digestion by both the human caecum and its associated appendix is negligible. Regardless of whether one accepts evolutionary theory or not, the human appendix is a rudiment of the caecum that is useless as a normal mammalian, cellulose-digesting caecum. Thus, by all accounts the vermiform appendix remains a valid and classic example of a human vestige.

Vermiform AppendixAuthor: Steven L Lee, MD, Chief, Pediatric Surgery, Department of Surgery, Kaiser-Permanente, Los Angeles Medical CenterCoauthor(s): Shant Shekherdimian, MD, Consulting Surgeon, Department of Surgery, Kaiser Foundation Hospital; Jeffrey J DuBois, MD, Consulting Staff, Division of Pediatric Surgery, Kaiser Permanente, North Sacramento Medical CenterContributor Information and Disclosures

Updated: Nov 24, 2008

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Introduction

In 1886, Reginald H. Fitz, a Harvard pathologist, first described the clinical condition of acute appendicitis.1 He correctly pointed out the importance of its early diagnosis and timely treatment, based on his analysis of 257 cases of perforating inflammation of the appendix and 209 cases of typhlitis or perityphlitis.2

A few years later, Charles McBurney described the clinical findings prior to rupture and advocated early surgical intervention. Despite aggressive intervention, mortality and morbidity rates remained high through the rest of the 19th century and the first half of the 20th century. The

mortality rate associated with appendicitis declined with the introduction of antibiotics and with the development of anesthesia and better perioperative care.

Currently, the diagnosis of acute appendicitis remains a challenge. Only slightly more than half of patients present with classic signs and symptoms of acute appendicitis. Atypical presentations often lead to a delay in diagnosis, perforation, prolonged hospitalization, and increased morbidity.3 Thus, all clinicians must be knowledgeable about diagnosing and managing this disease process.

For excellent patient education resources, visit eMedicine's Esophagus, Stomach, and Intestine Center. Also, see eMedicine's patient education articles, Appendicitis and Abdominal Pain in Adults.

History of the Procedure

The appendix was probably first noted as early as the Egyptian civilization (3000 BC). During the mummification process, abdominal parts were removed and placed in Coptic jars with inscriptions describing the contents. When these jars were uncovered, inscriptions referring to the "worm of the intestine" were discovered.4

Aristotle and Galen did not identify the appendix because they both dissected lower animals, which do not have appendices. Celsus, however, probably discovered the appendix because he was allowed to dissect criminals executed by Caesar.4 Leonardo da Vinci first depicted the appendix in anatomic drawings in 1492.5 In 1521, Jacopo Beregari da Capri, a professor of anatomy in Bologna, identified the appendix as an anatomic structure. In the 1500s, Vesalius (1543) and Pare (1582) referred to the appendix as the caecum. Laurentine compared the appendix to a twisted worm in 1600, and Phillipe Verheyen coined the term appendix vermiformis in 1710.4

Problem

Acute appendicitis remains one of the most common surgical diseases encountered by physicians. When appendicitis manifests in its classic form, it is easily diagnosed and treated. Unfortunately, these classic symptoms occur in just over half of patients with acute appendicitis; therefore, an accurate and timely diagnosis of atypical appendicitis remains clinically challenging and one of the most commonly missed problems in the emergency department. Furthermore, the consequence of missing appendicitis, thus leading to perforation, significantly increases morbidity and prolongs hospitalization.6

Frequency

In Western countries, approximately 7% of individuals develop appendicitis at some time during their lives. Approximately 200,000 appendectomies are performed annually in the United States.1

The peak incidence of acute appendicitis has gradually declined to about half of its peak incidence in the early 20th century, with the current annual incidence of 1 per 1000 population in the United States and 86 cases for every 100,000 persons worldwide.7,8

Acute appendicitis is less common in Africa and in parts of Asia because of the high-residue diets of the inhabitants.

Etiology

Appendicitis results from obstruction of the lumen of the appendix. Obstruction may be from lymphoid hyperplasia (60%), fecalith or fecal stasis (35%), foreign body (4%), and tumors (1%).9

Pathophysiology

The basic pathophysiology of appendicitis is obstruction of the lumen of the appendix followed by infection. In 60% of patients, obstruction is caused by hyperplasia of the submucosal follicles. This form of obstruction is mostly observed in children and is known as catarrhal appendicitis. A fecalith or fecal stasis causes luminal obstruction 35% of the time and is usually observed in adults. Obstruction may also be caused by foreign bodies (4%) and tumors (1%).

Following obstruction, an increase in mucous production occurs, and this leads to increased pressure. With increased pressure and stasis from obstruction, bacterial overgrowth ensues. The mucus then turns into pus that causes a further increase in luminal pressure. This leads to distention of the appendix and visceral pain, which is typically located in the epigastric or periumbilical region.

As the luminal pressure continues to increase, lymphatic obstruction occurs, leading to an edematous appendix. This stage is known as acute or focal appendicitis. The overlying parietal peritoneum becomes irritated, and the pain now localizes to the right lower quadrant (RLQ). This series of events results in the classic migrating abdominal pain described in patients with appendicitis.

Further increase in pressure leads to venous obstruction, causing edema and ischemia of the appendix. At this stage, bacterial invasion of the wall of the appendix occurs and is known as acute suppurative appendicitis. Finally, with continued pressure increases, venous thrombosis and arterial compromise occur, leading to gangrene and perforation.9 If the body successfully walls off the perforation, the pain may actually improve. However, symptoms do not completely resolve. Patients may still have underlying right lower quadrant pain, decreased appetite, change in bowel habits (eg, diarrhea, constipation), or intermittent low-grade fever. If the perforation is not successfully walled off, then diffuse peritonitis will develop.

Presentation

The classic presentation of a patient with appendicitis includes a history of initial periumbilical or epigastric abdominal pain migrating to the RLQ. The pain is gradual in onset and

progressively worsens. Anorexia, nausea, and vomiting are typically associated with the disease. In early appendicitis, the patient is initially afebrile or has a low-grade fever. Higher fevers are associated with a perforated appendix.3

On physical examination, the patient is usually lying still, as movement worsens the pain. Having the patient cough elicits localized pain in the RLQ. Local tenderness to palpation is usually observed. Percussion tenderness is also noted in this area. Tenderness on the right side during rectal examination may occur, whereas pelvic and testicular examination findings are normal. Other signs (eg, Rovsing, psoas, obturator) are unreliable and typically occur late in the disease process.3

Unfortunately, only 55% of patients with appendicitis present with classic history and physical findings. This is because the early signs and symptoms are primarily dependent upon the location of the tip of the appendix, which is highly variable.9

Indications

Indications for surgical consultation

A surgeon should evaluate any patient with classic migrating abdominal pain and RLQ tenderness. Because only a little more than half of patients with appendicitis present with a classic history and physical findings, acute appendicitis should be on the list of possible diagnoses for any patient with abdominal pain. Thus, a surgeon should also evaluate patients with focal RLQ tenderness or progressively worsening abdominal pain.

To minimize the time between presentation and appendectomy, obtain surgical consultation prior to performing additional diagnostic studies, such as CT scan, ultrasound, and technetium (Tc)-labeled WBC scan.3

Indications for operation

Any patient with suspected appendicitis who has (1) persistent pain and becomes febrile, (2) an increasing WBC count, or (3) worsening clinical examination findings should undergo appendectomy or at least diagnostic laparoscopy. In patients with an atypical presentation, the most important determination for appendectomy is serial physical examinations. The WBC count often does not increase after the patient is admitted and hydrated; therefore, any patient sent home from the emergency department should undergo a follow-up evaluation the next day.3

Relevant Anatomy

Embryologically, the appendix is a continuation of the cecum and is first delineated during the fifth month of gestation. The appendix does not elongate as rapidly as the rest of the colon, thus forming a wormlike structure.1

The appendix averages 10 cm in length but can range from 2-20 cm. The wall of the appendix consists of 2 layers of muscle, an inner circular and outer longitudinal. The longitudinal layer is a continuation of the taeniae coli. The appendix is lined by colonic epithelium.1

Few submucosal lymphoid follicles are noted at birth. These follicles enlarge, peak from 12-20 years, and then decrease. This correlates with the incidence of appendicitis.

Blood supply to the appendix is mainly from the appendicular artery, a branch of the ileocolic artery. This artery courses through the mesoappendix posterior to the terminal ileum. An accessory appendicular artery can branch from the posterior cecal artery. This artery can lead to significant intraoperative and postoperative hemorrhage and should be searched for carefully and ligated once the main appendicular artery is controlled.9

The base of the appendix is fairly constant and is located at the posteromedial wall of the cecum about 2.5 cm below the ileocecal valve. This is also where the taeniae converge.9

The base is at a constant location, whereas the position of the tip of the appendix varies. In 65% of patients, the tip is located in a retrocecal position; in 30%, it is located at the brim or in the true pelvis; and, in 5%, it is extraperitoneal, situated behind the cecum, ascending colon, or distal ileum. The location of the tip of the appendix determines early signs and symptoms.

Contraindications

No contraindications to performing an appendectomy in patients with suspected appendicitis exist; however, patients with a well-developed abscess (detected on CT scan) following perforated appendicitis may be initially treated with percutaneous drainage and intravenous antibiotics.

Once bowel function resumes, the patient may be discharged on oral antibiotics (total IV plus PO antibiotics for 7-10 d) with consideration for interval appendectomy in 6 weeks.10

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Wikipedia

Vermiform appendixInfobox Anatomy Name = Vermiform Appendix Latin = appendix vermiformis GraySubject = 249 GrayPage = 1178

Caption = Arteries of cecum and vermiform appendix. (Appendix visible at lower right, labeled as "vermiform process").

Caption2 = Normal location of the appendix relative to other organs of the digestive system (frontal view).

Precursor = Midgut System = Digestive Artery = appendicular artery Vein = appendicular vein MeshName = Appendix MeshNumber = A03.556.124.526.209.290 DorlandsPre = a_54 DorlandsSuf = 12147735 In human anatomy, the appendix (or vermiform appendix; also cecal (or caecal) appendix; also vermix) is a blind ended tube connected to the cecum (or caecum), from which it develops embryologically. The cecum is a pouch-like structure of the colon. The appendix is near the junction of the small intestine and the large intestine.

The term "vermiform" comes from Latin and means "worm-like in appearance".

ize and location

The appendix averages 10 cm in length, but can range from 2 to 20 cm. The diameter of the appendix is usually between 7 and 8 mm. The longest appendix ever removed measured 26 cm in Zagreb, Croatia. [http://www.guinnessworldrecords.com/records/human_body/body_parts/largest_appendix_removed.aspx Guinness world record for longest appendix removed.] ] The appendix is located in the lower right quadrant of the abdomen, or more specifically, the right iliac fossa.Paterson-Brown S. The acute abdomen and intestinal obstruction. Chapter 15 in Garden O.J., Bradbury A.W., Forsythe J.L.R., Parks R.W. (2007) Principles and Practise of Surgery, Fifth Edition, Churchill Livingstone Elsevier.] Its position within the abdomen corresponds to a point on the surface known as McBurney's point (see below). While the base of the appendix is at a fairly constant location, 2 cm below the ileocaecal valve , the location of the tip of the appendix can vary from being retrocaecal (74% ) to being in the pelvis to being extraperitoneal. In rare individuals with situs inversus, the appendix may be located in the lower left side.

Function

Given the appendix's propensity to cause death via infection, and the general good health of people who have had their appendix removed, the purpose of the appendix has mystified scientists for some time. There have been cases of people who have been found, usually on laparoscopy or laparotomy, to have a congenital absence of an appendix. There have been no reports of impaired immune or gastrointestinal function in these people.

Vestigiality

The most common explanation is that the appendix is a vestigial structure which now has no purpose. In " [http://onlinebooks.library.upenn.edu/webbin/gutbook/lookup?num=1043 The Story of Evolution] ", Joseph McCabe argued thus:

The vermiform appendage—in which some recent medical writers have vainly endeavoured to find a utility—is the shrunken remainder of a large and normal intestine of a remote ancestor. This interpretation of it would stand even if it were found to have a certain use in the human

body. Vestigial organs are sometimes pressed into a secondary use when their original function has been lost.

One potential ancestral purpose put forth by Darwin Darwin, Charles (1871) "Jim's Jesus". "The Descent of Man, and Selection in Relation to Sex". John Murray: London.] was that the appendix was used for digesting leaves as primates. Over time, we have eaten fewer vegetables and have evolved, over thousands of years, for this organ to be smaller to make room for our stomach. It may be a vestigial organ of ancient man that has degraded down to nearly nothing over the course of evolution. Evidence can be seen in herbivorous animals such as the Koala. The cecum of the koala is attached to the juncture of the small and large intestines and is very long, enabling it to host bacteria specific for cellulose breakdown. Early man’s ancestor must have also relied upon this system and lived on a diet rich in foliage. As man began to eat more easily digested foods, they became less reliant on cellulose-rich plants for energy. The cecum became less necessary for digestion and mutations that previously had been deleterious were no longer selected against. These alleles became more frequent and the cecum continued to shrink. After thousands of years, the once-necessary cecum has degraded to what we see today; the appendix.

Evolutionary theorists have suggested that natural selection selects for larger appendices because smaller and thinner appendices would be more susceptible to inflammation and disease [cite news|title=The old curiosity shop|work=New Scientist|date=2008-05-17|url=http://www.newscientist.com/channel/being-human/mg19826562.100-vestigial-organs-remnants-of-evolution.html] .

Immune Use

Loren G. Martin, a professor of physiology at Oklahoma State University, argues that the appendix has a function in fetuses and adults. [cite news|url=http://www.sciam.com/article.cfm?id=what-is-the-function-of-t|title=What is the function of the human appendix? Did it once have a purpose that has since been lost?|work=Scientific American|date=1999-10-21|accessdate=2008-07-01] Endocrine cells have been found in the appendix of 11 week old fetuses that contribute to "biological control (homeostatic) mechanisms." In adults, Martin argues that the appendix acts as a lymphatic organ. The appendix is experimentally verified as being rich in infection-fighting lymphoid cells, suggesting that it might play a role in the immune system. Zahid [Zahid, A. (2004) "The vermiform appendix: not a useless organ." J Coll Physicians Surg Pak. 14:256-258. [http://www.ncbi.nlm.nih.gov/entrez/query.fcgi?cmd=Retrieve&db=PubMed&list_uids=15228837&dopt=Abstract PubMed] ] suggests that it plays a role in both manufacturing hormones in fetal development as well as functioning to 'train' the immune system, exposing the body to antigens in order that it can produce antibodies. He notes that doctors in the last decade have stopped removing the appendix during other surgical procedures as a routine precaution, because it can be successfully transplanted into the urinary tract to rebuild a sphincter muscle and reconstruct a functional bladder.

Latest Interpretation: Maintaining gut flora

Although it was long accepted that the immune tissue, called gut associated lymphoid tissue, surrounding the appendix and elsewhere in the gut carries out a number of important functions, explanations were lacking for the distinctive shape of the appendix and its apparent lack of importance as judged by an absence of side-effects following appendectomy. Robbins Pathologic

Basis of Disease, 4th edition, 1989, pages 902-903 ] William Parker, Randy Bollinger, and colleagues at Duke University proposed that the appendix serves as a haven for useful bacteria when illness flushes those bacteria from the rest of the intestines. [cite news|url=http://www.msnbc.msn.com/id/21153898/|title=Scientists may have found appendix’s purpose: Seemingly useless organ may produce, protect good germs for your gut|date=2007-10-05|accessdate=2008-07-01|work=MSNBC] Bollinger, R.R., Barbas, A.S., Bush, E.L., Lin, S.S. & Parker. W. (2007) Biofilms in the large bowel suggest an apparent function of the human vermiform appendix. J. Theoretical Biology. doi:10.1016/j.jtbi.2007.08.032.] This proposal is based on a new understanding of how the immune system supports the growth of beneficial intestinal bacteria [ Sonnenburg JL, LT Angenent, JI Gordon. Getting a grip on things: how do communities of bacterial symbionts become established in our intestine? Nature Immunology. 2004;5:569-73 ] [ Everett ML, D Palestrant, SE Miller, RR Bollinger, W Parker. Immune exclusion and immune inclusion: a new model of host-bacterial interactions in the gut. Clinical and Applied Immunology Reviews. 2004;5:321-332. ] , in combination with many well-known features of the appendix, including its architecture and its association with copious amounts of immune tissue. Such a function is expected to be useful in a culture lacking modern sanitation and healthcare practice, where diarrhea may be prevalent. Current epidemiological data [ Statistics on the cause of death in developed countries collected by the World Health Organization in 2001 show that acute diarrhea is not the fourth leading cause of disease-related death in developing countries (data summarized by The Bill and Melinda Gates Foundation).Fact|date=December 2007 Two of the other leading causes of death are expected to have exerted limited or no selection pressure on humans in the distant past because one (HIV-AIDS) only very recently emerged and another (ischaemic heart disease) primarily affects people in their post-reproductive years. Thus, acute diarrhea may have been one of the primary disease-related selection pressures on the human population in the past. (Lower respiratory tract infection (pneumonia) is the remaining of the top four leading causes of disease-related death in third world countries.) ] show that diarrhea is one of the leading causes of death in developing countries, indicating that a role of the appendix as an aid in recovering beneficial bacteria following diarrhea may be extremely important in the absence of modern health and sanitation practices.

Diseases

The most common diseases of the appendix (in humans) are appendicitis and carcinoid tumors.Appendix cancer accounts for about 1 in 200 of all gastrointestinal malignancies. Adenomas also (rarely) present.

Appendicitis (or epityphlitis) is a condition characterized by inflammation of the appendix. Pain often begins in the center of the abdomen, corresponding to the appendix's development as part of the embryonic midgut. This pain is typically a dull, poorly localised, visceral pain.

As the inflammation progresses, the pain begins to localise more clearly to the right lower quadrant, as the peritoneum becomes inflamed. This peritoneal inflammation, or peritonitis, results in rebound tenderness (pain upon "removal" of pressure rather than "application" of pressure). In particular, it presents at McBurney's point, 1/3 of the way along a line drawn from the Anterior Superior Iliac Spine to the Umbilicus. Typically, point (skin) pain is not present until the parietal peritoneum is inflamed as well. Fever and an immune system response are also characteristic of appendicitis.

Many cases of appendicitis require removal of the inflamed appendix, either by laparotomy or laparoscopy. Untreated, the appendix may rupture, leading to peritonitis, followed by shock, and, if still untreated, death.

The surgical removal of the vermiform appendix is called an appendicectomy (or appendectomy). This procedure is normally performed as an emergency procedure, when the patient is suffering from acute appendicitis. In the absence of surgical facilities, intravenous antibiotics are used to delay or avoid the onset of sepsis; it is now recognized that many cases will resolve when treated non-operatively. In some cases the appendicitis resolves completely; more often, an inflammatory mass forms around the appendix. This is a relative contraindication to surgery.