A medical shunt is a device that diverts fluid or blood from one area of the body to another, typically to relieve pressure or facilitate a physiological process. These devices are surgically implanted, serving as bypasses to redirect fluids for absorption or external processing. Shunts are designed to ensure continuous flow and are tailored to address specific medical conditions.
Common Shunt Types and Their Placement
Medical shunts are placed in various locations, forming specific pathways within the body.
A common type is the ventriculoperitoneal (VP) shunt, which manages excess cerebrospinal fluid (CSF). One end is placed in a brain ventricle, often the lateral ventricle, to drain CSF. The tubing then runs under the skin, usually behind the ear and down the neck and chest, with the other end inserted into the peritoneal cavity in the abdomen, where the fluid is absorbed.
Another type, the ventriculoatrial (VA) shunt, also drains CSF from the brain’s ventricles. Its distal end is routed to the heart’s right atrium, typically through a neck vein. Lumboperitoneal (LP) shunts offer an alternative CSF diversion, with one end placed in the lumbar subarachnoid space of the spinal canal, often between two lumbar vertebrae. The shunt then extends under the skin to the peritoneal cavity in the abdomen for absorption.
For blood flow conditions, portosystemic shunts are used, such as the transjugular intrahepatic portosystemic shunt (TIPS). This shunt is created within the liver, forming a channel between a portal vein branch and a hepatic vein. The procedure is typically accessed via the jugular vein in the neck, redirecting blood flow to reduce pressure in the portal system. Dialysis access shunts, like arteriovenous (AV) fistulas or grafts, facilitate hemodialysis. An AV fistula directly connects an artery to a vein, usually in the arm, while an AV graft uses a synthetic tube for this connection, providing an accessible site for repeated dialysis treatments.
Conditions Necessitating Shunt Placement
Shunts manage conditions where the body’s natural fluid or blood flow is disrupted.
Hydrocephalus, characterized by excess CSF in the brain, is a common reason for shunt placement. VP or VA shunts divert this CSF, relieving brain pressure. This intervention helps prevent brain tissue damage and alleviates symptoms associated with elevated intracranial pressure.
Idiopathic intracranial hypertension (IIH), also known as pseudotumor cerebri, involves increased intracranial pressure without a clear cause, often leading to severe headaches and vision problems. LP or VP shunts drain CSF to reduce this pressure, aiming to protect eyesight. Normal Pressure Hydrocephalus (NPH), affecting older individuals, can also be treated with shunts, often VP shunts, to improve symptoms like gait disturbances and cognitive changes.
Portal hypertension, a complication of liver diseases like cirrhosis, results in elevated blood pressure in the portal vein system. A TIPS shunt reduces this pressure, managing complications such as variceal bleeding and fluid accumulation in the abdomen. For individuals with end-stage renal disease, dialysis access shunts provide a reliable, long-term access point for hemodialysis, a life-sustaining treatment that filters waste products from the blood when the kidneys fail.
Understanding Shunt Components
Medical shunts share common components that manage fluid or blood flow, regardless of their specific placement. These parts include catheters, a valve or regulating device, and sometimes a reservoir.
Catheters are flexible tubes that serve as conduits for fluid or blood. For CSF shunts, a proximal catheter is placed at the fluid collection site, such as a brain ventricle or the lumbar spine, while a distal catheter directs fluid to its absorption site. These catheters are typically made of biocompatible materials like silicone elastomer, chosen for their flexibility and minimal tissue reaction.
A valve or regulating device controls the direction, amount, and pressure of fluid flow within the shunt system. These valves ensure fluid drains at an appropriate rate, preventing both over-drainage and under-drainage. Some valves are fixed, while others are adjustable or programmable, allowing clinicians to non-invasively change settings after implantation using specialized tools.
An optional component in some shunt systems is a reservoir, a small chamber that can be felt under the skin. Reservoirs allow medical professionals to access the system for testing shunt function, measuring pressure, or withdrawing fluid samples.