Arteriovenous fistula, abbreviated as AVF, constitutes a pathological or surgical connection between an artery and vein. It can be present in any region of the body.
Arteriovenous fistulas (AVFs) are pathological or surgical vascular connections between arteries and veins. They can be congenital or acquired defects, for example after a penetrating trauma or an aneurysmal rupture. The symptomatology depends on the location and regional anatomy of AVF. Surgical AVF is used for long-term vascular access in hemodialysis.
Usually, acquired AVFs lead to a mass that can be palpated, transmits pulses, and a bruit can be heard during auscultation. These masses are commonly observed in an extremity previously affected by a significant traumatization. Symptoms of high-output congestive heart failure may also be reported, most frequently if the flow via the AVF is greater than 1/5 of the cardiac output, and include peripheral edema, cough, fatigue, shortness of breath, and ascites .
AVFs may lead to serious complications such as hemorrhage and neurological impairment .
With regard to congenital AVFs, the region where they are formed dictates the symptomatology. More specifically:
Symptoms may fail to arise for years after the patient is born. Similarly to acquired AVFs, congenital AVFs located on the extremities induce peripheral edema and hypertrophy of the extremity in young patients. This manifestation is aggravated when the AVF is found in the lower part of the extremity . The clinical picture may be further complicated with the onset of ulcers, thromboembolic events, and cardiac failure  .
A considerable number of patients presenting with pulmonary AVFs are also diagnosed with vascular anomalies in the nasopharynx, liver, spleen and gastrointestinal tract, as manifestations of the Rendu-Osler-Weber syndrome. Pulmonary arteriovenous fistulas per se may lead to dyspnea on exertion, symptoms related to high-output congestive heart failure, pulmonary hypertension, and hypoxemia  . Compensatory polycythemia may develop, leading to non-specific symptoms, such as a headache and fatigue.
They can lead to manifestations related to myelopathy.
These AVFs can be related to Rendu-Osler-Weber syndrome, Ehlers-Danlos syndrome, and biliary atresia.
Patients frequently have varicosities. Symptoms associated with diminished perfusion of the limb can also arise.
Radiological modalities employed in the diagnosis of arteriovenous fistulas are computed tomography (CT) angiography, magnetic resonance (MR) angiography, digital subtraction angiography (DSA), and color Doppler ultrasound.
CT angiography is a successful diagnostic procedure which produces accurate and specific findings. The modality reveals contrast material entering the vein prematurely during the arterial phase and illustrate the precise location of AVF. It has been found that CT angiography yields results that are in agreement with digital subtraction angiography . The latter can provide particularly accurate information concerning the arteries involvement in the fistula formation and can help to create a diagram concerning the optimal therapeutic intervention.
Color Doppler ultrasound demonstrates blood flow patterns and velocity in the vessels. Frequent findings are an arterial-like wave in the adjacent vein and turbulent flow at the site of a connection. MRA is performed, in order to diagnose and clearly delineate the borders of AVFs  .
MR angiography could be performed in order to visualize AVFs more precisely  .
With regard to blood laboratory studies, patients affected by extensive AVFs may exhibit abnormal results such as thrombocytopenia, elevated PT and PTT time, decreased fibrinogen, and prolonged euglobulin clot lysis time.