Anastomosis : an important clinical term with multiple non-standardized definitions and no formal classification

Introduction Anastomosis is a frequently used and important clinical term with multiple meanings and no obvious standardized definition or classification. Anastomosis differs in meaning depending on whether the context is anatomical, physiological or surgical, which leads to confusion. Few textbooks offer a complete or working definition of ‘anastomosis’ even though the term is used ubiquitously. This review investigated the definition of ‘anastomosis’. Materials and methods A literature search was conducted on the most commonly used texts: anatomical, physiological and surgical along with common web-based resources to examine the use of ‘anastomosis’ and to determine the completeness of the definition. Results The literature search revealed that the most common definition, when presented, was ‘a communication of one vessel to another’. Collectively, three separate definitions were identified. Surprisingly, many textbooks did not offer a definition of anastomosis; those that did provided a single and limited definition. Conclusion Our suggested definition is: ‘The communication of a luminal vessel with another region of itself or branch of itself with another luminal vessel from a separate origin, or when capillary beds from separate origins interact to maintain tissue viability’. Due to its clinical importance, the results of our review suggest the term anastomosis could be defined comprehensively and classified. Introduction Anastomosis is a term that has existed since classical antiquity. The term can be traced back in recorded history to Erasistratus (Figure 1) and Galen (Figure 2), who both believed that the arteries are linked to the veins at their extremities by extremely fine, imperceptibly small, connecting channels1. This single definition has evolved into several distinct variations. At least three groups (anatomists, physiologists and clinicians) have variations on the term anastomosis and all are different. Some anatomists on the topic of the Circle of Willis may state that the Circle of Willis is an anastomosis amongst cerebral arterial vessels. They may further clarify that the Circle of Willis fails to provide adequate blood to an obstructed area, thus leading to a cerebrovascular accident ( Figure 3). Therefore, this type of definition is a structural, rather than a functional arterial anastomosis. Some physiologists may describe an anastomosis as the sharing of two sets of capillary beds and may note the importance of including an anastomosis to ensure tissue viability. This would represent a functional tissue viability anastomosis ( Figure 4). A surgeon might give an example of an anastomosis using a procedure referred to as an end-toend bowel anastomosis (Figure 5); * Corresponding author Email: bbenninger@westernu.edu Departments of Medical Anatomical Sciences1, Neuromuscular Medicine2, Family Practice3, Western University of Health Sciences, COMP– Northwest, Lebanon, OR, USA. Faculty, College of Dental Medicine4, Pomona CA. Departments of Orthopaedics5 and General Surgery6, Samaritan Health Services, Corvallis, OR, USA. Departments of Oral Maxillofacial Surgery7, Surgery8, Orthopaedics & Rehabilitation9, Oregon Health & Science University, Portland, OR, USA. Figure 1: Erasistratus, the father of physiology.


Introduction
Anastomosis is a term that has existed since classical antiquity.The term can be traced back in recorded history to Erasistratus (Figure 1) and Galen (Figure 2), who both believed that the arteries are linked to the veins at their extremities by extremely fine, imperceptibly small, connecting channels 1 .
This single definition has evolved into several distinct variations.At least three groups (anatomists, physiologists and clinicians) have variations on the term anastomosis and all are different.Some anatomists on the topic of the Circle of Willis may state that the Circle of Willis is an anastomosis amongst cerebral arterial vessels.They may further clarify that the Circle of Willis fails to provide adequate blood to an obstructed area, thus leading to a cerebrovascular accident ( Figure 3).
Therefore, this type of definition is a structural, rather than a functional arterial anastomosis.Some physiologists may describe an anastomosis as the sharing of two sets of capillary beds and may note the importance of including an anastomosis to ensure tissue viability.This would represent a functional tissue viability anastomosis ( Figure 4).A surgeon might give an example of an anastomosis using a procedure referred to as an end-toend bowel anastomosis (Figure 5);    In each illustrated case, the person using the term anastomosis is correct, but significant differences exist in the meaning of the term in each case.Some uses suggest tissue death and others tissue preservation.Without a comprehensive definition, such a range of uses may dilute the precision and breadth of the term anastomosis making it difficult to appreciate the uses of the term anastomosis.
This review set out to locate original definition(s) and current interpretations and to provide a more comprehensive definition if appropriate.

Materials and methods
A literature search was conducted examining historical and modern definitions of anastomosis.Historical collections, institutes, libraries and rare books were investigated and analysed regarding the definition of anastomosis.Our examinations of modern sources included commonly used anatomy, medical and surgical textbooks, atlases and Internet sources.

Results
Historical definitions of anastomosis are shown in Table 1. Figure 6 shows the frequency of the term  (άναστομόειυ, to bring to a mouth).The intercommunication of vessels.Anastomotic arteries of the thigh, etc., branches of the brachial, femoral, etc., whereby the collateral circulation is established after ligature for aneurysm, etc.The term has been inaccurately used of the junction of nerve-filaments.A., Crucial, an arterial anastomosis in the upper part of the thigh, formed by the anastomotic branch of the sciatic, the first perforating, the internal circumflex, and the transverse branch of the external circumflex.A., Intestinal, an operation consisting in establishing a communication between the intestine above and that below the obstruction, in cases of intestinal obstruction.In this way the impermeable portion of the bowel is excluded from the fecal circulation.
anastomosis in popular modern textbooks and the frequency of a definition for anastomosis.

Discussion
The objective of this review was to identify the definition of anastomo-

Classifications of Anastomos is Explanation Example
Type I The connection of one luminal vessel to another.Surgically created to circumvent or remove an obstruction.
Type II Non-viable anatomical anastomos is.Circle of Willis.

Type III
The overlap of capillary beds that ensures tissue viability even if one of the prominent feeders into the capillary beds is obstructed.
Capillary beds of the face.are direct connections between smaller arteries and veins' 15 .Some definitions described anastomosis as a convergence or joining of arteries 16,17 ; others described it as a network 18 .None of the six common definitions found in textbooks offered a comprehensive definition.
In clinical and didactic settings, this term is voiced frequently with varied meanings with which the learner is unlikely to be familiar.For example, the term anastomosis implies a different outcome when it is used by the following experts: • Surgeons-bowel anastomosis, femoral-popliteal anastomosis • Anatomists-cerebral circulation -Circle of Willis (nonviable tissue) • Physiologists-the sharing of two sets of capillary beds (viable tissue).
The difference in clinical relevance is significant enough to create a comprehensive definition, which would include a table of subcategories ( Table 2).Our suggested definition is: 'The communication of a luminal vessel with another region of itself, or branch of itself, or with another luminal vessel from a separate origin with or without the sharing of capillary beds'.

Conclusion
This review found that the term anastomosis was generally undefined in many modern texts.In the few instances where a definition is given, the definitions were inconsistent and no comprehensive universal definition could be identified.This review suggests a universal definition, 'The communication of a luminal vessel with another region of itself, or branch of itself, or with another luminal vessel from a separate origin with or without the sharing of capillary beds'.This will allow trainees to better understand this very common term.
Departments of Medical Anatomical Sciences1 , Neuromuscular Medicine 2 , Family Practice 3 , Western University of Health Sciences, COMP-Northwest, Lebanon, OR, USA.Faculty, College of Dental Medicine 4 , Pomona CA.Departments of Orthopaedics 5 and General Surgery 6 , Samaritan Health Services, Corvallis, OR, USA.Departments of Oral Maxillofacial Surgery 7 , Surgery 8 , Orthopaedics & Rehabilitation 9 , Oregon Health & Science University, Portland, OR, USA.

Figure 4 :
Figure 4: Capillary as an example of functional tissue viability anastomosis.

Figure 3 :
Figure 3: Circle of Willis: an example of a structural anastomosis.

Figure 6 :
Figure 6: Graph showing the frequency of the term anastomosis in popular modern textbooks and the frequency of a definition for anastomosis.

Table 1 Chronological account of the usage of the term anastomosis. Year Source Definition
Expounding Such Words, as Being Terms of Art, or Otherwise Derived From the Greek and Latin, Are Dark to the English Reader 2 .An opening of the Mouths of Veins, by which means Blood iffues.1715The Physical Dictionary.Wherein The Terms of Anatomy, the Names and Causes of Diseases, Chyrurgical Instruments, and their Use, are accurately describ'd 3 .An Effluxion of the Blood, the Lympha or Chyle, at the meeting of Vessels that close not narrowly.It is also taken for the mutual opening of Veins and Arteries into one another, as some long ago falslyimagin'd; for this were to offer Violence to the Laws of Circulation, yet it is not impossible neither, since Veins open into Veins, and Ar-Anatomists and surgeons imply by this term the communications of the blood-vessels with each other, or their running and opening into each other, by which the continuance of a free circulation of the blood is greatly ensured, and the danger of mortification lessened.The immense importance of this part of our structure in all cases in which the main artery or veins of a limb are obliterated, is particularly conspicuous in the disease called aneurism.
teries into Arteries; as is plain in the Spermatick Vessels, the Plexus Choroides, Rete mirabile, &c.1787 Lexicon Physico-Medicum; or, a New Medicinal Dictionary.Explaining the Difficult Terms Used in the Several Branches of the Profession, And in Such Parts of Natural Philosophy, As are Introductory thereto 4 .From ανα, through, and ςσμα, the mouth.To relax, or open the mouths of the vessels.This sometimes expresses such an aperture of the mouths of the vessels as lets out their contents: but more commonly a unison between the arteries and veins, where the former open into the latter; or where an artery ceases any longer to be so, and begins to be a vein.1819TheLondon Medical Dictionary; Including, Under Distinct Heads, Every Branch of Medicine, Viz.Anatomy, Physiology, and Pathology, the Practice of Physic and Surgery, Therapeutics, and MateriaMedica; With Whatever Relates to Medicine in Natural Philosophy, Chemistry, and Natural History 5 .Anatomists use the word to express the inosculation of the arteries and veins, or their running into one another.The menses, discharged, are said to be discharged by anastomosis, i.e. by the opening the mouths of the vessels into the uterus.1832ADictionary of Practical Surgery: Comprehending All the Most Interesting Improvements, Form the Earliest Times Down to the Present Period; An Account of the Instruments and Remedies Employed in Surgery; the Etymology and Signification of the Principal Terms; and Numerous References to Ancient and Modern Works: Forming a 'Catalogue Raisonné' or Surgical Literature 6 .(Fromανα,through, and στομα, a mouth.)(στόμα,a mouth).The communication of vessels with each other, as of the arteries with the veins, which by touching at numerous points, form a network of reticulation.See Inosculation.

Table 1 (continued) 1874
A Dictionary of Medical Science: Containing a Concise Explanation of the Various Subjects and Terms of Anatomy, Physiology, Pathology, Hygiene, Therapeutics, Medical Chemistry, Pharmacology, Pharmacy, Surgery, Obstetrics, Medical Jurisprudence, and Dentistry; Notices of Climate, and of Mineral Waters; Formulae for Officinal, Empirical, and Dietetic Preparations; with the Accentuation and Etymology of the Terms, and the French and Other Synonyms 9 .(αναστομωσις,fromana,στομα,'a mouth', and osis.)Inoscula'tioseuReu'niovaso'-rum,Exanastomo'sis,Concur'sus, Inosculat'tion,(F.)Anastomose,Aboucement.Communication between two vessels.By considering the nerves to be channels, in which a nervous fluid circulates, their communication has been called Anastomosis.By means of anastomoses, if the course of a fluid be arrested in one vessel, it can proceed along others.(αναστομοω, to bring to a mouth).The junction or intercommunication of vessels.Anastomotic arteries of the thigh, etc., branches of the brachial, femoral, etc., whereby the collateral circulation is established after ligature for aneurysm, etc.The term has been inaccurately used of the junction of nervefilaments.1890TheNational Medical Dictionary: Including English, French, German, Italian, and Latin Technical Terms Used in Medicine and the Collateral Sciences, and a Series of Tables of Useful Data 12 .1.Union of two vessels by which their canals become continuous.2. Union or conjunction between two nerves.