Ananastomosis (/əˌnæstəˈmoʊsɪs/,pl.:anastomoses) is a connection or opening between two things (especially cavities or passages) that are normally diverging or branching, such as betweenblood vessels,leaf veins, orstreams. Such a connection may be normal (such as theforamen ovale in a fetus' heart) or abnormal (such as thepatent foramen ovale in an adult's heart); it may be acquired (such as anarteriovenous fistula) or innate (such as the arteriovenous shunt of ametarteriole); and it may be natural (such as the aforementioned examples) or artificial (such as asurgical anastomosis). The reestablishment of an anastomosis that had become blocked is called a reanastomosis. Anastomoses that are abnormal, whethercongenital or acquired, are often calledfistulas.
The term is used inmedicine,[1]biology,mycology,geology, andgeography.
Anastomosis: medical or Modern Latin, from Greek ἀναστόμωσις, anastomosis, "outlet, opening", Greek ana- "up, on, upon", stoma "mouth", "to furnish with a mouth".[2] Thus the-stom- syllable is cognate with that ofstoma in botany orstoma in medicine.
An anastomosis is the connection of two normally divergent structures.[3] It refers to connections betweenblood vessels or between other tubular structures such as loops ofintestine.
Incirculatory anastomoses, many arteries naturally anastomose with each other; for example, theinferior epigastric artery andsuperior epigastric artery, or the anterior and/or posterior communicating arteries in theCircle of Willis in the brain. The circulatory anastomosis is further divided into arterial and venous anastomosis. Arterial anastomosis includes actual arterial anastomosis (e.g.,palmar arch,plantar arch) and potential arterial anastomosis (e.g.coronary arteries and cortical branch ofcerebral arteries). Anastomoses also form alternative routes aroundcapillary beds in areas that do not need a large blood supply, thus helping regulatesystemic blood flow.[citation needed]
Surgical anastomosis occurs when segments ofintestine, blood vessel, or any other structure are connected together surgically (anastomosed). Examples include arterial anastomosis inbypass surgery, intestinal anastomosis after a piece of intestine has been resected,Roux-en-Y anastomosis andureteroureterostomy. Surgical anastomosis techniques include linear stapled anastomosis,[4] hand sewn anastomosis,[4] end-to-end anastomosis (EEA).[5] Anastomosis can be performed by hand or with an anastomosis assist device.[6] Studies have been performed comparing various anastomosis approaches taking into account surgical "time and cost, postoperative anastomotic bleeding, leakage, and stricture".[7]
Anastomotic leakage in colorectal cancer surgery
Failure of an intestinal anastomosis with leakage of intestinal content in to the abdominal cavity is one of the most severe complications after bowel surgery. The severity of anastomotic leakage varies ranging from mild with minimal impact on the patient to severe and potentially fatal, with negative impact on both short- and long-term outcomes. The incidence has not changed in recent decades, despite improvement in surgical techniques, prehabilitation and perioperative care. Anastomotic leakage after rectal cancer surgery is higher and documented to occur in 9-11%, after colon resection the incidence of leakage is lower and about 6%.[8][9] Systemic factors contributing to anastomotic failure include sepsis, anemia, diabetes mellitus, previous irradiation, malnutrition, steroid use, smoking, heavy alcohol consumption, obesity and certain disease conditions like Chron’s disease.[10][11]
Signs of an anastomotic leak include fever, abdominal pain or peritonitis, leukocytosis and tachycardia or new-onset arrythmias. Anastomotic leakage is usually diagnosed 5-8 days post-surgery.[11] A CT scan with pneumoperitoneum and significant free fluid or inflammatory changes around the anastomosis are suggestive of an anastomotic failure. Depending on the magnitude of the defect and leak different treatments are indicated. A localized anastomotic leak without systemic sepsis or peritonitis can be managed with antibiotics and if possible, drainage of the abscess. Anastomotic leaks associated with peritonitis or systemic sepsis requires an operation with either revision of the anastomosis if feasible or fecal diversion proximally or at the site of the anastomosis with a stoma.[10]
Pathological anastomosis results fromtrauma ordisease and may involveveins,arteries, orintestines. These are usually referred to asfistulas. In the cases of veins or arteries, traumatic fistulas usually occur between artery and vein. Traumatic intestinal fistulas usually occur between two loops of intestine (entero-enteric fistula) or intestine andskin (enterocutaneous fistula).Portacaval anastomosis, by contrast, is an anastomosis between a vein of theportal circulation and a vein of thesystemic circulation, which allows blood to bypass theliver in patients withportal hypertension, often resulting inhemorrhoids,esophageal varices, orcaput medusae.[citation needed]
Inevolution, anastomosis is a recombination of evolutionary lineage. Conventional accounts of evolutionary lineage present themselves as the branching out of species into novel forms. Under anastomosis, species might recombine after initial branching out, such as in the case of recent research that shows that ancestral populations along human and chimpanzee lineages may have interbred after an initial branching event.[12] The concept of anastomosis also applies to the theory ofsymbiogenesis, in which newspecies emerge from the formation of novel symbiotic relationships.[citation needed]
Inmycology, anastomosis is the fusion between branches of the same or differenthyphae.[13] Hence the bifurcating fungal hyphae can form true reticulating networks. By sharing materials in the form of dissolvedions,hormones, andnucleotides, the fungus maintains bidirectional communication with itself. The fungal network might begin from several origins; several spores (i.e. by means ofconidial anastomosis tubes), several points of penetration, each a spreading circumference of absorption and assimilation. Once encountering the tip of another expanding, exploring self, the tips press against each other inpheromonal recognition or by an unknown recognition system, fusing to form a genetic singular clonal colony that can cover hectares called agenet or just microscopical areas.[14]
For fungi, anastomosis is also a component of reproduction. In some fungi, two differenthaploid mating types – if compatible – merge.Somatically, they form a morphologically similar mycelial wave front that continues to grow and explore. The significant difference is that eachseptated unit is binucleate, containing two unfusednuclei, i.e. one from each parent that eventually undergoeskaryogamy and meiosis to complete the sexual cycle.[citation needed]
Also the term "anastomosing" is used for mushroom gills which interlink and separate to form a network.[15]
The growth of astrangler fig around a host tree, with tendrils fusing together to form a mesh, is called anastomosing.[16]
Ingeology,veins ofquartz (or other) minerals can display anastomosis.[17]
Ductileshear zones frequently show anastomosing geometries of highly-strained rocks around lozenges of less-deformed material.[18]
Moltenlava flows sometimes flow in anastomosedlava channels[19] orlava tubes.[20]
In cave systems, anastomosis is the splitting of cave passages that later reconnect.[21]
Anastomosing rivers,anastomosing streams consist of multiple channels that divide and reconnect and are separated by semi-permanent banks formed of cohesive material, such that they are unlikely to migrate from one channel position to another. They can be confused withbraided rivers based on their planforms alone, but braided rivers are much shallower and more dynamic than anastomosing rivers. Some definitions require that an anastomosing river be made up of interconnected channels that enclose floodbasins,[22] again in contrast with braided rivers.
Rivers with anastomosedreaches include theMagdalena River inColombia,[23] the upperColumbia River inBritish Columbia, Canada,[24] theDrumheller Channels of theChanneled Scablands of the state of Washington, US, and the upperNarew River inPoland.[25] The termanabranch has been used for segments of anastomosing rivers.
Braided streams show anastomosing channels aroundchannel bars ofalluvium.[26]