bubble_chart Overview

Congenital arteriovenous fistula is caused by abnormal development of embryonic primordia during their evolution, leading to abnormal communication between arteries and veins. In the past, congenital arteriovenous fistulas have been given many names, such as cirsoid aneurysm, racemose aneurysm, angioma arterial plexiforme, congenital phlebarteriectasia, as well as Klippel-Trenaunary Syndrome and Parkes-Weber Syndrome. Malan and Puglionis proposed a simple classification method based on whether venous or arterial tissue predominates. They believed that the vast majority are venous-dominant.

bubble_chart Etiology

Primitive blood vessels and blood cells both originate from the mesodermal mesenchyme. In the early embryonic stage before somites form, some cells in the extraembryonic mesoderm of the yolk sac and body stalk aggregate to form cell clusters of varying sizes, known as blood islands. These blood islands gradually extend and interconnect to form primitive capillary plexuses. Arteries and veins originate from the same capillary plexus at the same time. The embryonic development of blood vessels can generally be divided into three stages: the plexiform stage, reticular stage, and vascular trunk formation stage. During the reticular stage, if dilated vascular communications aggregate and tend to fuse together, arteriovenous fistulas can form. Histologically, numerous parallel vessels with incomplete fusion and multiple interconnections can be observed, often extremely fine and referred to as micro-arteriovenous fistulas. During the vascular trunk formation stage, persistently extensive abnormal communications between major systemic arteries and veins are termed macro-arteriovenous fistulas. The exact cause of abnormal vascular primordium development leading to vascular malformations remains highly debated. Some scholars believe congenital arteriovenous fistulas are inherited through chromosomal abnormalities. However, in Desaive and Bessone's study of 840 congenital malformations, only 7 cases suggested a hereditary history. During early pregnancy, toxic infections, metabolic disturbances, abnormal fetal position, and compression trauma caused by abnormal umbilical cord position can affect normal fetal development. Endocrine and autonomic nervous system dysregulation may also influence the development of arteries, veins, and the lymphatic system.

bubble_chart Pathological Changes

Based on the size and location of the fistula, it can generally be classified into three types: ① Truncal arteriovenous fistula, where there are communicating branches between the main peripheral arteries and veins in the transverse axis. Most fistulas are relatively large, resulting in significant shunting between the artery and vein. Pathological sites may exhibit murmurs, tremors, varicose veins, and serpentine stirred pulse tumors. ② Aneurysmal arteriovenous fistula: numerous small communicating branches exist between the main peripheral arteries and veins in the transverse axis, often involving local soft tissues and bones, with tumor-like vascular dilation in the affected tissue. Generally, blood shunting is minimal, and there are no local murmurs or tremors. ③ Mixed type: multiple arteriovenous communications exhibiting both truncal and aneurysmal characteristics.

bubble_chart Clinical Manifestations

Most congenital arteriovenous fistulas are present at birth, usually latent, without any clinical symptoms, and do not attract parental attention. Factors such as endocrine influences during puberty, trauma, or excessive activity often trigger the activation of arteriovenous fistula lesions.

(1) Limb Overgrowth and Hypertrophy In adolescents whose bone epiphyses have not yet closed, the arteriovenous fistula is already present, so the affected limb is generally longer than the healthy side, with an increased circumference. This hypertrophy includes skeletal and soft tissue factors, such as bone elongation and cortical thickening. The limb length may exceed the healthy side by 2–5 cm. Patients often experience heaviness, swelling, and pain in the limb. Sometimes, lower back pain occurs due to pelvic tilt and spinal curvature caused by unequal limb lengths.

(2) Skin Birthmarks, Temperature, and Structural Changes Congenital arteriovenous fistulas often coexist with congenital hemangiomas in the same area, with the vascular lesion appearing as a capillary hemangioma—bluish-red, either flat or raised on the skin surface. Sizes vary, ranging from a few centimeters in diameter to encircling the entire limb. In cases of venous insufficiency, the skin may appear cyanotic; with arterial insufficiency, it may appear pale. Skin color can also change with posture. Skin temperature increases at the fistula site. Gilmon and Bolam reported a case where the skin temperature on the affected side was up to 1.5°C higher than the corresponding area on the healthy side. The temperature tends to normalize proximal to the fistula but decreases distally. Increased skin temperature is often accompanied by localized sweating. In cases of pulsatile masses due to arteriovenous fistulas, the skin may show erosive or atrophic changes, becoming thin and translucent. In areas of chronic venous stasis, the skin may harden, thicken, and lose elasticity.

(3) Varicose Veins, Ulcers, and Gangrene The presence of an arteriovenous fistula often first manifests as prominent local varicose veins. If the fistula is large, the varicose veins may pulsate. Complications such as ulcers, dermatitis, and bleeding may occur. In rare cases, due to impaired distal limb circulation, ulcers and gangrene may develop in the distal parts of the feet or hands.

bubble_chart Auxiliary Examination

(1) Stirred Pulse Angiography When deciding on surgical treatment and understanding the residual conditions of previously operated arteriovenous fistulas, stirred pulse angiography is required. Stirred pulse angiography can reveal arteriovenous communications, though it is sometimes challenging. If the angiography shows many abnormal clusters of blood vessels, it may be difficult to identify direct arteriovenous communications. The input main trunk in stirred pulse angiography may dilate and become tortuous due to increased blood flow. Diagnosis of congenital arteriovenous fistulas can be made based on changes such as contrast pooling at the fistula site, abdominal mass, and varicose output veins.

(2) Venous Blood Oxygen Examination The venous blood oxygen level at the lesion site is higher than that at the corresponding site on the healthy side.

bubble_chart Diagnosis

Based on medical history and physical examination, the diagnosis is generally not difficult. Congenital arteriovenous fistulas are accompanied by varicose veins. Therefore, in young adults or children, when varicose veins are found without obvious cause, especially if they are unilateral or in uncommon locations, the possibility of congenital arteriovenous fistulas should be considered. If the patient exhibits limb lengthening, thickening, excessive hair growth, or excessive sweating, the diagnosis becomes even more certain.

bubble_chart Treatment Measures

Congenital arteriovenous fistulas are often multiple, affecting various different planes. Sometimes the stirred pulse of the fistula may originate from more than one source, or a single stirred pulse may have numerous branching vessels, making complete resection of the extensive and numerous small arteriovenous fistulas extremely difficult. For cases with widespread lesions, most scholars advocate non-surgical treatment. Sako and Vacro reported the treatment experience of 32 cases of congenital arteriovenous fistulas, among which 21 underwent surgical treatment, with 5 cured, 8 improved, 6 worsened, and 2 unchanged. For congenital arteriovenous fistulas involving a single muscle tissue, limb function is not significantly affected after resection.

Indications: ① Congenital arteriovenous fistulas with rapid local growth; ② Cases accompanied by heart failure, lesions affecting adjacent nerves causing pain, or extensive lesions invading the skin and prone to injury with complications such as bleeding should undergo surgery as soon as possible.

1. Resection of arteriovenous fistula: The feeding vessels and the abnormally developed muscles involved are removed. For superficial and localized congenital arteriovenous fistulas, local resection or removal of the affected muscle group can yield satisfactory results. During extensive resection, care must be taken to protect nerves. For congenital arteriovenous fistulas in the neck or face, avoid injury to the facial nerve during resection; for lesions in the buttocks, avoid injury to the sciatic nerve. Tissue defects left after extensive arteriovenous fistula resection require vascular pedicle myocutaneous flap transplantation under a surgical microscope to repair the defect. Our hospital has performed local lesion resection on 7 cases of arteriovenous fistulas, with 6 achieving good postoperative results and 1 requiring amputation due to limb necrosis.

2. Proximal stirred pulse ligation of the arteriovenous fistula: For patients with extensive lesions, proximal stirred pulse ligation of the arteriovenous fistula can be performed. The ligated stirred pulse should be as close to the fistula as possible. However, stirred pulse ligation may lead to limb ischemia or gangrene, so careful consideration is required. Shanghai Zhongshan Hospital reported one case of congenital arteriovenous fistula extending from the shoulder to the forearm with extensive lesions. Subclavian stirred pulse ligation was performed, resulting in limb necrosis and pain, ultimately requiring shoulder disarticulation.

3. Ligation of the main arteriovenous branches of the fistula: For extensive or deep-seated arteriovenous fistulas accompanied by bleeding, infection, and ulceration, the main branches of the arteriovenous fistula can be identified through stirred pulse angiography. Separate ligation of the branching vessels can then be performed. Shanghai Zhongshan Hospital has treated 3 such cases with this method, all showing postoperative improvement.

4. Intravascular embolization therapy: Necoton first reported percutaneous catheter embolization for spinal hemangiomas in 1967, which was later also used to treat congenital arteriovenous fistulas.

(1) Embolic materials: Ideal embolic materials are radiopaque, non-toxic to the human body, and capable of permanently occluding stirred pulses or veins. Commonly used materials include gelatin sponge, silicone, isobutyl-2-cyanoacrylate, polyvinyl alcohol, and metal coils.

(2) Precautions for embolization: Before performing stirred pulse embolization, angiography of the lesion site is necessary to clearly identify the main feeding vessels and venous return of the congenital arteriovenous fistula. Based on the lesion location and blood flow characteristics, select different catheters and embolic materials with appropriate physicochemical properties. Care must be taken to prevent small embolic materials from passing through the fistula into the pulmonary stirred pulse. The catheter should be advanced as close to the embolization site as possible. Avoid reflux of embolic materials into the normal organ-supplying stirred pulses, especially in the face and neck. Under fluoroscopic guidance, slowly inject the embolic material.

(3) Complications: Patients may generally develop a high fever exceeding 39°C within 24 hours after embolization, likely due to muscle and tissue damage. Embolic materials may pass through the fistula into the pulmonary stirred pulse, causing pulmonary embolism. If aseptic techniques are not strictly followed during the procedure, sepsis may occur. Venous stasis can lead to secondary thrombosis, potentially resulting in pulmonary embolism.