Shunt

A shunt is a passage or conduit that diverts all or part of a flow, current, or signal from the main path. Shunts are used to redirect flow for measurement, regulation, safety, or relief of pressure. The term is used across engineering, medicine, and infrastructure to describe a bypass that preserves primary function while providing an alternative route.

In electrical engineering, a shunt typically refers to a low-resistance element placed in parallel with a load. A shunt resistor allows the current in a circuit to be measured by converting a small portion of the current into a measurable voltage drop. Because the resistor is of known small resistance, the majority of current remains through the main path. Shunts are also used in protective devices and current regulators to provide alternate paths during fault or overload conditions.

In medicine, implantable shunts create alternate fluid pathways to relieve pressure or drain excess fluid. A ventriculoperitoneal shunt diverts cerebrospinal fluid from the brain's ventricles to the abdominal cavity to treat hydrocephalus; other forms include ventriculoatrial and ventriculopleural shunts. Arteriovenous shunts connect an artery and vein to enable hemodialysis or to bypass obstructed vessels. Common considerations include the risk of infection, blockage, and over- or under-drainage, requiring regular monitoring and sometimes revision.

In infrastructure and civil contexts, shunts may be bypass lines or valves that redirect flow to maintain pressure, relieve surges, or balance systems in plumbing, heating, or drainage. In rail transport, 'shunting' refers to moving rail cars within a yard to assemble or detach trains.