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Shunt (medical)

In medicine, a shunt is a hole or passage which moves, or allows movement of, fluidfrom one part of the bodyto another. The term may describe either congenitalor acquiredshunts; and acquired shunts may be either biologicalor mechanical.

Inhaltsverzeichnis

1 Cardiac Shunt
- 1.1 Congenital
- 1.2 Acquired
  - 1.2.1 Biological
  - 1.2.2 Mechanical
2 Cerebral Shunt
- 2.1 Spitz-Holter
3 See also

Cardiac Shunt

Cardiac shunts may be described as right-to-left, left-to-rightor bidirectional, or as systemic-to-pulmonaryor pulmonary-to-systemic. The direction may be controlled by leftand/or right heartpressure, a biological or artificialvalve, or both. The presence of a shunt may also affect left and/or right heart pressure either beneficiallyor detrimentally.

Congenital

The most common congenitalheart defects(CHDs) which cause shunting are the atrial septal defect(ASD), ventricular septal defect(VSD), patent ductus arteriosus(PDA), and patent foramen ovale(PFO). In isolation, these defects may be asymptomatic, or they may produce symptomswhich can range from mild to severe, and which can either be acuteor have delayed onset. However, these shunts are often present in combination with other defects; in these cases, they may still be asymptomatic, mild or severe, acute or delayed, but they may also work to counteract the negative symptoms caused by another defect (as with d-Transposition of the great arteries).

Acquired

Biological

Some acquired shunts are modifications of congenital ones: a balloon septostomycan enlarge a foramen ovale(if performed on a newborn), PFO or ASD; or prostaglandincan be administered to a newborn to prevent the ductus arteriosusfrom closing. Biologicaltissuemay also be used to construct artificial passages.

Mechanical

Mechanicalshunts are used in some cases of CHD to control blood flowor blood pressure. One example is the modern version of the Blalock-Taussig shunt.

Cerebral Shunt

In cases of hydrocephalus, a one-way valveis used to drain excess cerebrospinal fluidfrom the brainand carry it to other parts of the body. This valve usually sits outside the skull, but beneath the skin, somewhere behind the ear.

Although a shunt generally works well, it may stop working if it disconnects, becomes blocked, or it is outgrown. If this happens the cerebrospinal fluid will begin to accumulate again and a number of physical symptoms will develop, some extremely serious, like seizures.

The shunt failure rate is also relatively high and it is not uncommon for patients to have multiple shunt revisions within their lifetime.

The diagnosis of cerebro-spinal buildup is complex and requires expertise.

Spitz-Holter

A common pediatric shunt is the Spitz-Holter shunt. It is a tiny one-way valve that releases controlled amounts of CSF from the brain to the heart. Spitz refers to the American neurosurgeon Eugene B. Spitz. Holter refers to the designer of the valve, John Holter, who was unable to save his son Casey from hydrocephalus, but his design, the Spitz-Holter valve/shunt, has helped millions around the world since the late 1950s.