Etiology and Classification
During the mid-stage of fetal vascular development, arteries not only run alongside accompanying veins but also maintain extensive connections with surrounding capillaries. After birth, these anastomoses gradually close, and arteries and veins follow separate courses. If the primitive plexiform vascular structure persists, abnormal connections of varying sizes, numbers, and types between arteries and veins are formed, creating arteriovenous fistulas (AVFs). These abnormalities typically remain latent during infancy and early childhood but rapidly progress and spread by school age or during adolescence, especially with increased physical activity. The condition may invade adjacent tissues, including muscles, bones, and nerves.
Clinical Manifestations
Arteriovenous fistulas most commonly occur in the head and neck region, followed by the extremities, trunk, and internal organs. Symptoms are generally mild or absent during infancy and early childhood, often presenting only as mild soft tissue hypertrophy. Significant clinical manifestations usually emerge during adolescence. The condition can be staged by severity according to the Schobinger classification:
- Stage I (Quiescent Stage): Asymptomatic, typically from birth to puberty. Lesions are not prominent and may present as port-wine stains or a regressing hemangioma-like appearance. Palpation may reveal localized warmth.
- Stage II (Expansion Stage): Usually begins at puberty, with the lesion increasing in size, darker skin discoloration, and involvement of the skin and deeper structures. Palpation may detect pulsation and thrill, while auscultation often reveals a bruit.
- Stage III (Destructive Stage): Symptoms include spontaneous necrosis, chronic ulcers, pain, and bleeding.
- Stage IV (Decompensation Stage): Persistent hemodynamic abnormalities may lead to complications such as "high-output, low-resistance" heart failure or cardiac insufficiency.
Examinations and Diagnosis
Diagnosis is based on typical clinical symptoms, including soft tissue hypertrophy present since birth or early childhood, progressive worsening with age, limb enlargement and elongation, localized warmth, and excessive perspiration. These findings are characteristic of arteriovenous fistula.
Treatment
Localized congenital arteriovenous fistulas respond well to surgical excision or ligation of the fistulous connections. However, treatment is challenging for extensive or multiple AVFs, and postoperative recurrence is common.