A shunt is a connection (fistula) between an artery (artery = high-pressure system) and a vein (low-pressure system). A shunt is therefore also called an arteriovenous fistula. Due to the increased blood flow in the vein, it expands over time and the wall becomes thicker. The shunt can then be punctured with needles and used for blood washing (dialysis) in kidney disease.
Here you will find further information and selected shunt surgeons.
In medicine, a shunt is referred to as a short circuit. This refers to a connection between two blood vessels that are normally separated.
Such a connection either occurs naturally or is created artificially by doctors. The purpose of creating a shunt is to support a therapy.
Natural shunts are, for example, congenital malformations that arise in the embryonic stage. Some shunts are normal (= physiological) in the embryonic stage and disappear after birth. An important example of this is the shunt between the large aorta and the pulmonary vein, which is important for embryonic circulation.
The most commonly surgically created shunt is the dialysis shunt. This usually involves creating a connection between the artery at the wrist and an adjacent vein on the arm (the left arm for right-handed patients and the right arm for left-handed patients). This shunt is called a ciminoshunt after the person who first described it. However, if the blood vessels on the forearm are too thin or calcified, the connection is made in the crook of the elbow or on the upper arm.
Illustration of a dialysis shunt © ひろみ きたはし| AdobeStock
Shunts can also occur unintentionally, which can subsequently cause problems. Examples include shunts after a puncture in the groin or wrist as part of a cardiac catheterization. This can result in a connection between the (deliberately punctured) artery and the (unintentionally punctured) vein, which expands over time. In extreme cases, the increased blood flow in the vein leads to a strain on the right heart (where the venous blood flows) and there is a risk of heart failure. It may then be necessary to close the shunt (= arteriovenous fistula) by surgery.
During dialysis, a blood vessel must be punctured with two thick needles in order to suck the blood out of the body via one needle and clean it in the dialysis machine. After the dialysis machine has taken over the function of the kidneys and removed toxins from the blood, the purified blood is returned to the body via the other needle. This blood washing normally has to be carried out 3 times a week and takes about 3-5 hours each time.
Dialysis shunt in use © Max Tactic | AdobeStock
In order for this blood washing to work well and be carried out within a few hours, the punctured vessel (shunt) must fulfill certain requirements:
In order to fulfill these requirements, the shunt must "mature", i.e. develop. This takes place after the connection between the artery (high pressure) and the vein has been created due to the increased blood pressure in the vein (normally low pressure). This maturing phase lasts approx. 4 - 8 weeks and should definitely be waited for. During the "maturing phase", premature lancing of the shunt vein can lead to complications, including closure of the shunt.
If the requirements for creating a shunt from the body's own vessels (so-called autologous shunts) are not met, plastic shunts (alloplastic shunts) can also be used. These are plastic tubes that are sewn between an artery and a vein and then regularly punctured after a certain period of time. The plastic shunts available today are very well tolerated. Rejection reactions hardly ever occur. However, the plastic can become infected. In addition, the development of constrictions or protrusions is significantly more common than with the body's own vessels. For this reason, alloplastic shunts should be avoided if possible and autologous variants should be preferred.
The placement of a shunt in the vascular system is not a physiological condition. Therefore, complications often occur in the shunt area. Under certain circumstances, these can result in a slowly progressing or abrupt closure of the shunt or its loss.
Common complications are
Many problems, such as constrictions, occlusions, protrusions or haematomas can be treated by widening or narrowing the diseased part and removing haematomas. A shunt infection can often be successfully treated with antibiotics, but sometimes the shunt has to be removed and replaced at a different location. If the shunt drains too much blood and leads to overloading or overloading of the heart and a circulatory disorder in the hand, it may be necessary to stop the shunt (= disconnection of the connection between the artery and vein).
There is no general answer to the question of how long a shunt lasts. Some shunts close for the first time after just a few weeks and then have problems again and again at regular intervals. Others are still working perfectly after 10 years. In general, however, upper arm shunts last longer than forearm shunts and autologous variants are more durable than alloplastic ones.
Nevertheless, if possible, the shunt should be placed as far away from the body (towards the hand) as possible, as renal insufficiency is a chronic disease. If kidney function is completely lost, recovery is not to be expected; blood washing is necessary for the rest of the patient's life. Consequently, all vessels in the arm should be used from bottom to top. If a forearm shunt no longer works over time, an upper arm shunt can then be created. However, if an upper arm shunt is created first, a forearm shunt cannot be implanted later.
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