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An anastomosis (, : anastomoses) is a connection or opening between two things (especially cavities or passages) that are normally diverging or branching, such as between , leaf veins, or . Such a connection may be normal (such as the foramen ovale in a fetus' heart) or abnormal (such as the patent foramen ovale in an adult's heart); it may be acquired (such as an arteriovenous fistula) or innate (such as the arteriovenous shunt of a metarteriole); and it may be natural (such as the aforementioned examples) or artificial (such as a surgical anastomosis). The reestablishment of an anastomosis that had become blocked is called a reanastomosis. Anastomoses that are abnormal, whether congenital or acquired, are often called .
The term is used in medicine, biology, mycology, geology, and geography.
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%.Snijders HS, Wouters MWJM, Van Leersum NJ, Kolfschoten NE, Henneman D, De Vries AC, et al. Meta-analysis of the risk for anastomotic leakage, the postoperative mortality caused by leakage in relation to the overall postoperative mortality. Eur J Surg Oncol EJSO. 2012 Nov;38(11):1013–9Meyer J, Naiken S, Christou N, Liot E, Toso C, Buchs NC, et al. Reducing anastomotic leak in colorectal surgery: The old dogmas and the new challenges. World J Gastroenterol. 2019 Sep 14;25(34):5017–25 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.Chen C. The Art of Bowel Anastomosis. Scand J Surg. 2012 Dec;101(4):238–40Chiarello MM, Fransvea P, Cariati M, Adams NJ, Bianchi V, Brisinda G. Anastomotic leakage in colorectal cancer surgery. Surg Oncol. 2022 Mar;40:101708
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. 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.
For fungi, anastomosis is also a component of reproduction. In some fungi, two different haploid 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 each septum unit is binucleate, containing two unfused cell nucleus, i.e. one from each parent that eventually undergoes karyogamy and meiosis to complete the sexual cycle.
Also the term "anastomosing" is used for mushroom gills which interlink and separate to form a network.
Ductile frequently show anastomosing geometries of highly-strained rocks around lozenges of less-deformed material.
Molten lava flows sometimes flow in anastomosed or .
In cave systems, anastomosis is the splitting of cave passages that later reconnect.
Rivers with anastomosed River reach include the Magdalena River in Colombia, the upper Columbia River in British Columbia, Canada,Abbado, D., Slingerland, R.L., and Smith, N.D., 2005, The origin of anastomosis in the upper Columbia River, British Columbia, Canada: In Blum, M.D., Marriott, S., and Leclair. S. (eds.), Fluvial Sedimentology VII, Internat. Assoc. Sedim. Special Publ. 35. the Drumheller Channels of the Channeled Scablands of the state of Washington, US, and the upper Narew River in Poland. The term anabranch has been used for segments of anastomosing rivers.
Braided river show anastomosing channels around Braid bar of alluvium.
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