Arteriovenous fistulas are very common for people on dialysis. Depending on their size, where they are and why they happened, fistulas can be harmless or very helpful.
Normally, blood flows from arteries into capillaries, then into veins. Fistulas allow blood to flow directly from an artery into a vein without going through the capillaries.
Diagnosis
A spinal dural arterio-venous fistula (SDAVF) is a communication between arteries and veins in the dura, or outer lining of the spinal cord. It’s most common in the thoracic and lumbar spine, but it can also form in the upper arms and legs. It may develop as a result of diagnostic renal biopsy, radio-frequency ablation of renal tumors or other surgeries, or from injury from blunt trauma or stab wounds.
Fistulas are usually diagnosed by examining the area with your doctor and listening to blood flow with a stethoscope. A fistula makes a distinctive humming sound that sounds different from the pulsating sounds of your normal blood vessels. You might also feel a thrill on the skin over the fistula, and you might notice a reddish or brownish color in that area.
Your doctor might order an MRI to look at the structure of your fistula and the area around it. An MRI is an imaging test that uses magnetic fields and radio waves to create detailed pictures of your body’s tissues and organs. A radiologist can then inject a dye into the blood vessels to help doctors see the blood flow better. The dye shows up on X-ray and MRI images.
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If you have a spinal SDAVF, your doctor might also want to try a procedure called endovascular embolization. This is an outpatient surgery that involves passing a small catheter into the blood vessels that feed your spinal cord fistula. Then, your doctor releases glue-like material or tiny particles into the blood vessels to close off your fistula.
Some fistulas can grow large enough to divert too much blood from the arm or leg. This can cause a painful lump, open sores that won’t heal and swelling of the skin in the affected area. Some fistulas also allow small blood clots to travel through the fistula into the lungs, where they can block blood flow and cause a stroke.
Other symptoms include a feeling of fullness in the affected arm or leg, a bluish or gray color in the area of the fistula and, in some cases, a rash. Your doctor might prescribe blood-thinning medications to help prevent clots from forming in your blood vessels, and you might need a surgery to disconnect or close your fistula if these medications aren’t effective.
Symptoms
An arteriovenous fistula is an abnormal direct communication between a blood vessel (artery) and a vein. Fistulas develop in the arms and legs, but can also be found elsewhere in the body. They are most common in the neck, spine and liver. The connection between the high-pressure artery and the low-pressure vein increases the flow of blood through the area, which often makes it swell. It can also produce a clicking, humming sound that doctors hear with a special stethoscope called a venous auscultation.
The outlook and symptoms of a fistula depend on its size, location and cause. Smaller fistulas in certain locations usually don’t require treatment and may even close by themselves. Larger fistulas that are in critical locations can cause complications and sometimes even death.
Dialysis is the most common reason for a fistula to be created. It helps create a wider, thicker vein that’s better able to handle needles and can carry more blood into and out of your body during dialysis.
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Most unintentional fistulas are acquired, meaning they happen because of an injury or some other event that damages your arteries and veins that lie side-by-side. This can include a penetrating wound, such as a stab or gunshot wound. It can also result from a medical procedure, such as a catheterisation or coronary angiography.
Fistulas can also be congenital, which means they are present at birth. This can be the case with pulmonary fistulas in your lungs, which are commonly caused by genetic conditions like hereditary hemorrhagic telangiectasia and Osler-Weber-Rendu disease.
Most of the time, doctors can feel an AV fistula by feeling the vibration that’s created when the blood flows over it. Doctors can also test a fistula’s blood flow by using an imaging test called duplex ultrasound mapping, which uses an instrument that sends ultra-high-frequency sound waves to bounce off red blood cells and measure how fast the blood flows. This test is especially useful for detecting a thrombosis or clot near a fistula. Doctors can also use a CT scan or an echocardiogram to check the size and position of your arteries and veins.
Treatment
A fistula is an abnormal connection between two blood vessels. AV fistulas are usually made for dialysis purposes to provide a larger, thicker vein that can better handle the needles used for dialysis. Sometimes these fistulas develop complications that require treatment, such as clubbing of the fingers (a condition where the fingers turn blue because the blood flow pattern is diverted to the vein and not to the finger tips).
If a patient has an acquired DAVF in which the vascular connections are side-to-side instead of end-to-end, surgery can be performed to close the connection. During this procedure, the surgeon will sew shut the holes in the artery and vein. Generally, the surgeon will perform this surgery as soon as possible after diagnosis of the problem. This will prevent recurrence and allow for an effective seal to be established.
Alternatively, a physician can use a minimally invasive procedure called catheter embolization to treat a DAVF. During this procedure, the physician inserts a thin tube into a blood vessel and then guides it to the area of the DAVF. The physician then injects different types of materials, such as metal coils or glue, to block the DAVF. This can be an excellent alternative to surgical ligation of the proximal feeding artery. However, care needs to be taken in selecting the appropriate material and size of coils based on the territory distal to the DAVF, the size of the feeding artery, flow dynamics, and the risk of inadvertent nontarget embolization via the AVF.
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Other treatment options may include radiation therapy, in which the provider uses a machine to target the dural arteriovenous fistula and destroy it with high-energy radiation. This is only used in certain cases, however, and should only be done by a trained, experienced provider.
For congenital dAVFs, the healthcare provider may choose to wait and monitor the symptoms of the condition. They will likely recommend that the person wear gloves and wash their hands frequently to avoid infecting the AV fistula or other blood vessels in the hand. They will also advise the person to seek emergency medical attention if they experience any signs or symptoms that indicate they are not getting enough blood flow to the affected area, such as pain, swelling of the arm or leg, and bluish skin coloration.
Complications
Fistulas aren’t a set-it-and-forget-it kind of thing. They need to be looked after regularly, and with the right care they can last much longer than CVCs, so they’re often a better choice for people doing dialysis long-term.
Like a road, your AV fistula needs to be cleared of “traffic jams” in order to keep working well. One of these problems is called stenosis, and it happens when the blood vessels get narrower or blocked up so that the blood flow slows down or stops completely. Another issue is when the fistula becomes infected, which can lead to pain, redness, and fever. Some infections can be very serious, and if they aren’t treated promptly, they may cause a condition called steal syndrome. This occurs when the AV fistula starts drawing more blood from the artery and redirecting it to the vein (again, usually in your arm).
This can cause your arteries to stretch and swell up, but the veins can’t handle that. Over time, this can strain your heart and cause it to start working harder than normal to try to force the blood to flow normally. Eventually this can lead to a heart attack.
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The good news is that these issues aren’t common, and they can be prevented with the right treatment. Regular check-ups with your doctor, using a needle that’s the right size for your AV fistula, and getting the right treatment for infections can all make your fistula stronger and healthier.
It’s also important to be aware of when to call for help. Any time you have signs of internal bleeding or not having enough blood flowing to your arm, especially a hand or foot, call for emergency medical attention right away. Your healthcare provider can tell you other signs and symptoms to watch out for, such as color changes in your skin near the fistula or on your whole body, or sudden, severe pain. They can also tailor that information to fit your particular health situation, such as any other conditions you have and the treatments you receive. They can also talk to you about other ways to reduce your risk of complications, including taking antibiotics and wearing compression stockings.
