anastomoses

Anastomosis refers to a connection between two hollow or tubular structures, such as blood vessels, lymphatics, or ducts, that allows fluid or other contents to pass between them. An anastomosis can be a natural, congenital feature or a surgically created connection designed to restore continuity after tissue resection or to bypass a blockage. The term encompasses various configurations and functions across organ systems.

In the circulatory system, anastomoses provide alternative routes for blood flow and contribute to collateral circulation. They include arterial-to-arterial connections, venous-to-venous connections, and arteriovenous connections, as well as intervascular networks such as capillary beds. Examples in humans include the cerebral circle of Willis, bronchial–pulmonary artery connections, and coronary collaterals that may develop after coronary obstruction. Lymphatic and biliary anastomoses also occur, connecting lymphatic vessels or biliary ducts.

Common modes of surgical or clinical anastomosis are end-to-end, end-to-side, and side-to-side configurations, depending on how the ends of two structures are joined. An arteriovenous fistula is a deliberate AV anastomosis created for hemodialysis access. Intraorgan anastomoses, such as intestinal or biliary anastomoses, restore continuity after tissue resection or rerouting.

Patency and proper healing of anastomoses are essential for function. Complications can include leakage, thrombosis, stenosis, or fistula formation. In disease, natural anastomotic pathways can become clinically relevant, for example in portal hypertension where portal-systemic collaterals form varices, or in tissue ischemia when collateral vessels enlarge.

Anastomosis is a fundamental concept across anatomy, surgery, and pathology, reflecting the body's capacity to connect conduits and adapt to changes in flow or obstruction.