Arteriovenous Fistula

Arteriovenous (AV) fistula refers to an abnormal channel between an artery and vein. 

In the presence of this abnormal connection blood flows directly from the artery to the vein, bypassing the capillaries. Thus, the tissues and organs supplied by capillaries receive reduced amount of blood.

 AV fistulas may be congenital or acquired. Fistula produces symptoms of arterial insufficiency. When left untreated AV fistula result in blood flow in veins under higher pressure than normal. 

This may result in enlargement and bulging of veins. Untreated AV fistulas may lead to serious complications. Fistulas are more commonly found in the leg, but may develop in other parts of the body as well. 

An AV fistula is created by surgical methods in kidney disease patients who need dialysis.

Small Arteriovenous fistulas often remain asymptomatic. Symptoms are seen associated with large-sized fistulas in the blood vessels. 

This includes: 

• Enlarged, bulging veins that looks like varicose veins
• Swelling in arms and legs
• Numbness, pain, and cramping in legs
• Low blood pressure
• Weakness and fatigue
• Lightheadedness
• Heart failure

Pulmonary AV fistula, or fistula in the lungs, is a serious condition characterized by bluish colored skin, clubbing of fingers, and blood in cough. 

Gastrointestinal AV fistula may result in bleeding in the alimentary canal. 

AV fistulas may be congenital or acquired and the actual cause for Arteriovenous fistulas is not known. Abnormal development of the blood vessels is implied in the formation of fistulas in blood vessels. 

Acquired AV fistulas are caused by several factors. 

Cardiac catheterization is a procedure in which a catheter is inserted into the blood vessel for diagnosis or treatment of certain conditions. 

In some rare cases, the catheter may cross the artery and vein during the procedure and lead to the formation of an AV fistula. 

Injuries like stab wounds and gunshots are piercing wounds which possibly lead to fistulas, particularly if the injury is in a place where the two blood vessels are side by side. 

Certain genetic conditions like Osler-Weber-Rendu disease result in abnormal development of blood vessels in lungs, leading to pulmonary AV fistulas.

AV fistulas are created surgically in patients with late-stage kidney disease. These artificial fistulas widen the vein and make it easier for inserting the dialysis needle. 

Making diagnose of Arteriovenous fistula is done by several tests.

Presence of a machinery-like murmur while listening to the blood flow using a stethoscope is the first indication of the presence of AV fistula.

 Other tests are used to confirm the diagnosis of AV fistula. The most commonly used technique for diagnosis of AV fistula is duplex ultrasound, a procedure in which a transducer is placed in the affected area. This technique helps to assess the rate of blood flow in the blood vessel. 

CT angiogram helps to visualize the blood flow through arteries and veins, including the bypassing of capillaries. AV fistulas in the deep veins are visualized using MRI. 

Magnetic resonance angiography (MRA) is a modified version of MRI in which a special contrast dye is used to visualize the flow of blood in arteries and veins.

Small-sized Arteriovenous fistulas do not require any specific treatment. Monitoring of the progress of the fistulas are suggested, if the fistulas do not cause any health issues. In some cases, the fistulas may resolve on their own without any treatment. 

Ultrasound-guided compression is recommended for AV fistulas in legs. The procedure compresses the fistula and inhibits the blood flow to the affected blood vessel. 

Catheter embolization is a procedure in which a catheter is guided to the region of AV fistula.

A small stent is placed at the site to restore blood flow in the normal route. This procedure enables the person to return to normal activities within a week. 

Surgery is recommended for AV fistulas that cannot be treated with catheter embolization. 

There are no standard methods for prevention of congenital Arteriovenous fistulas. Acquired fistulas can be prevented by avoiding piercing injuries on skin. 

A well-performed procedure like cardiac catheterization also helps to prevent the formation of fistulas. Patients with surgically created AV fistula are monitored continuously for complications.

Many alternative remedies like photodynamic therapy, antiangiogenic therapy, and sclerotherapy are being tried for controlling symptoms of AV fistulas.

Lifestyle modifications are necessary in order to cope with Arteriovenous fistula.

Surgically created AV fistulas require good care. 

Cleanliness is utmost important in avoiding infections. 

Avoid tight clothing and accessories in the access area of the dialysis needle. 

Avoid sleeping with the access arm under the head, and remember to check the pulse of access arm daily.

Arteriovenous fistulas may lead to some serious complications like heart failure, blood clots, bleeding, and leg pain. Blood clots caused by AV fistulas may lead to deep vein thrombosis and pulmonary embolism.