Etiology and Classification
Traumatic arteriovenous fistula primarily results from trauma or iatrogenic injury. Stab wounds are the leading cause of traumatic arteriovenous fistulas, followed by gunshot wounds, blunt trauma, and others. Iatrogenic injuries are most commonly associated with percutaneous arterial puncture for interventional diagnosis and treatment. Rare causes include aneurysmal rupture into adjacent veins or vascular wall rupture due to bacterial infection, leading to an arteriovenous fistula.
Clinical Manifestations
The progression of the condition is divided into the following stages:
Acute Phase
A pulsatile mass often develops at the site of injury, and thrill and vascular bruit are commonly present. The distal artery beyond the fistula generally remains palpable.
Chronic Phase
High-pressure arterial blood directly shunting into veins through the fistula causes an increase in venous pressure. Localized symptoms are often very pronounced: coarse, continuous vascular bruits can typically be heard on both sides of the fistula, neighboring veins become visibly dilated, and vascular bruits and thrills are apparent. The skin temperature around the fistula is elevated. In regions distal to the fistula, particularly in areas such as the foot, arterial blood supply diminishes, and venous congestion leads to trophic changes. These changes may include thin, shiny skin, hyperpigmentation, and ulcer formation. Fistulas with larger openings, proximity to the heart, or originating from arteries with larger diameters can significantly increase venous return to the heart through direct shunting of blood. This change can result in progressive cardiac enlargement and eventually lead to heart failure.
Examinations and Diagnosis
Diagnosis is primarily based on clinical findings, including the appearance of a pulsatile mass at the site of trauma, thrill on palpation, coarse continuous vascular bruits, superficial vein dilation, ischemic changes in distal tissue, or signs of venous congestion. The following diagnostic modalities are useful:
- Doppler Ultrasound: Visualization of arterial blood shunting into veins through the fistula.
- CTA (Computed Tomography Angiography): Accurate in diagnosing most arteriovenous fistulas in the neck, proximal limbs, and abdominal cavity.
- Angiography: Larger arteriovenous fistulas are typically directly visualized, with adjacent veins significantly dilated and filling simultaneously with the arteries. The distal arterial segments beyond the fistula may not be fully visualized. Smaller fistulas may not directly reveal the abnormal opening, but simultaneous visualization of adjacent arteries and veins near the fistula location serves as a diagnostic indicator. In cases with a history of hematoma formation, aneurysmal dilation may be observed on the arterial and/or venous sides near the fistula.
Treatment
Conservative Management
Doppler ultrasound is used to assess the size and location of iatrogenic arteriovenous fistulas. Compression under ultrasound guidance is suitable for patients in whom the fistulous track between the artery and vein is relatively long.
Endovascular Therapy
Endovascular management is indicated for patients with stable conditions, appropriate anatomical structures, poor surgical tolerance, or lesions located in areas difficult to access surgically. Treatment options include catheter-based embolization, stent-graft placement, or a combination of these approaches.
Surgical Treatment
Emergency surgery is required for acute arteriovenous fistulas presenting with active bleeding, cardiac decompensation, diminished arterial pulsation, or acute ischemia of internal organs or limbs. Patients with chronic arteriovenous fistulas whose lesions or anatomical features are unsuitable for endovascular repair, as well as young and healthy individuals with aorto-caval fistulas, should also be considered for surgical repair.