Vascular Malformations and Congenital/Acquired Arteriovenous Fistulas

59.1Definition and presentation

Vascular anomalies are defined by lesion biology and flow physiology following the International Society for the Study of Vascular Anomalies (ISSVA) classification Terminology Errors 2023 · ISSVA 2018. Accurate classification separates true malformations from vascular tumors, differentiates low-flow from high-flow hemodynamics, and distinguishes isolated lesions from syndromic disease ISSVA Molecular 2022.

Clinical presentation diverges strictly by flow characteristics:

• Low-flow lesions (venous and lymphatic malformations): Compressibility, bluish discoloration, dependency-related pain, phlebolith-type tenderness, recurrent swelling, lymphatic vesicles, fluid leakage, and a history of cellulitis Japanese Guidelines 2017 · Peripheral AVM 2021.
• High-flow lesions (arteriovenous malformations and shunts): Warmth, pulsatility, bruit, thrill, rapid expansion, bleeding, ulceration, prominent draining veins, distal perfusion changes, and high-output cardiac features Japanese Guidelines 2017 · Peripheral AVM 2021.

Syndromic variants, including Hereditary Hemorrhagic Telangiectasia (HHT), Klippel-Trenaunay, Parkes-Weber, and CLOVES syndromes, present with local lesions but require systemic screening, family evaluation, and molecular-context assessment ISSVA Molecular 2022.

59.2Diagnosis and imaging stratification

Imaging delineates the anatomic and hemodynamic consequences required for intervention planning. Assessment is matched to the suspected flow physiology Peripheral AVM 2021 · ISSVA 2018.

• Low-flow malformation imaging: Defines lesion extent, tissue planes, venous drainage patterns, lymphatic predominance, and proximity to nerves, skin, mucosa, the orbit, the airway, and functional structures.
• High-flow AVM imaging: Hemodynamic mapping is mandatory before intervention. Assessment defines arterial inflow, nidus configuration, venous outflow, tissue involvement, and cardiac consequence. Doppler ultrasound characterises flow, cross-sectional MRI/MRA (with CTA) maps lesion extent, and selective catheter angiography defines angioarchitecture and the nidus before treatment Peripheral AVM 2021.
• Arteriovenous fistula imaging: Localizes the exact level of arterial-to-venous communication, identifies the chronicity of the shunt, and evaluates distal perfusion alongside venous and cardiac burden.

59.3Treatment decision and intervention thresholds

Intervention is indicated by clinical consequence rather than cosmetic appearance or imaging volume alone. The decision to treat is anchored in specific endpoints: pain, swelling, functional limitation, tissue integrity, cellulitis or thrombosis history, deformity, bleeding, and overall quality of life Low-flow Outcomes 2024 · QoL Systematic Review 2018 · Venous Malformation Management 2021.

Treatment decision sequence requires stratification by flow and systemic features:

1. Differentiate true malformations from vascular tumors and acquired shunts.
2. Isolate acquired traumatic or iatrogenic fistulas for direct anatomic closure under vascular trauma protocols.
3. Identify syndromic markers that route the patient to systemic medical or screening pathways rather than local intervention.
4. Separate low-flow lesions (managed by compression, staged sclerotherapy, or targeted excision) from high-flow AVMs (managed by staged embolisation and multidisciplinary resection).
5. Establish the clinical endpoint before treating a high-flow AVM. Embolisation is deployed to reduce flow, control a bleeding point, close portions of a nidus, or prepare for surgical resection Peripheral AVM 2021 · Transarterial AVM 2018.

High-flow AVMs progress through the Schobinger clinical stages, and intervention is timed to stage rather than to imaging bulk. Stage I (quiescent) is a warm pink-blue stain with arteriovenous shunting on Doppler. Stage II (expansion) adds enlargement, pulsation, thrill, bruit, and tortuous tense draining veins. Stage III (destruction) adds dystrophic skin change, ulceration, bleeding, intractable pain, or tissue necrosis. Stage IV (decompensation) adds high-output cardiac failure. Asymptomatic Stage I is observed; symptomatic Stage II and Stage III are the usual thresholds for staged embolisation, and Stage III-IV disease mandates treatment Peripheral AVM 2021.

Image-guided sclerotherapy for low-flow lesions requires patient consent for anticipated post-procedural swelling and acknowledges risks of skin injury, neuropathy, tissue necrosis, airway compromise, or functional loss, heavily dependent on the anatomic compartment Venous Malformation Management 2021. Diffuse malformations extending through critical planes are generally poor candidates for surgical excision. Genotype-directed systemic therapy stands as a distinct arm for selected patients, sirolimus (an mTOR inhibitor) for complex slow-flow venous and lymphatic malformations and alpelisib (a PIK3CA inhibitor) for PIK3CA-related overgrowth spectrum, reserved for disease burden exceeding what compression, sclerotherapy, embolisation, or excision can control, and requiring specialist selection with longitudinal toxicity monitoring Sirolimus Meta-analysis 2025 · VASE Trial 2023 · PIK3CA Targeted Therapy 2018.

59.4Hereditary hemorrhagic telangiectasia and pulmonary AVMs

Hereditary hemorrhagic telangiectasia shifts management from local lesion intervention to systemic risk prevention. Features prompting referral to a dedicated HHT pathway include recurrent epistaxis, mucocutaneous telangiectasia, family history, hypoxaemia, paradoxical embolic events, brain abscess, gastrointestinal bleeding, anemia, or multi-territory AVMs HHT Guidelines · 2020. These features map to the four Curacao criteria: spontaneous recurrent epistaxis; mucocutaneous telangiectasia at characteristic sites (lips, oral cavity, fingers, nose); visceral AVMs (pulmonary, hepatic, cerebral, spinal, or gastrointestinal); and a first-degree relative with HHT. Diagnosis is definite with three or more criteria, possible or suspected with two, and unlikely with fewer than two; genetic testing confirms the diagnosis when clinical criteria are indeterminate.

Pulmonary AVMs generate right-to-left shunting that permits paradoxical embolism and sepsis, alongside hypoxaemia. Embolisation of pulmonary AVMs is indicated to prevent these systemic neurologic and infectious consequences, using a distinct treatment logic from the local tissue-preservation approach applied to peripheral AVMs HHT Guidelines · 2020 · Pulmonary AVM Update · 2020 · Cochrane PAVM 2018. Selection has moved away from a strict size cutoff. A feeding-artery diameter of 3 mm or more was the historic threshold for embolisation, but current guidance recommends transcatheter closure of every pulmonary AVM technically amenable to treatment, regardless of feeding-artery size. In the HHT population, visible lesions are not universally excised or embolised; intervention is prioritized for epistaxis control, anemia management, and the prevention of paradoxical events. HHT management also includes genetic counseling, molecular testing, and screening of first-degree relatives for pulmonary, cerebral, and hepatic AVMs.

59.5Congenital and acquired arteriovenous fistulas

Pathological arteriovenous fistulas are direct high-pressure shunts and are managed separately from venous or lymphatic malformations Japanese Guidelines 2017 · ISSVA 2018.

Congenital AVFs incorporate into the circulation over years, resulting in enlarged feeding arteries, arterialised veins, and cardiac adaptation. Treatment aims for closure, exclusion, or flow reduction to relieve venous hypertension and preserve distal perfusion Japanese Guidelines 2017 · ISSVA 2018.

Acquired AVFs arise from trauma, arterial puncture, catheter placement, or operation. They present with a pulsatile mass, bruit, thrill, acute venous hypertension, limb swelling, distal ischemic symptoms, bleeding, pseudoaneurysm formation, or high-output physiology. These are managed strictly as vascular trauma injuries, using open, endovascular, or hybrid exclusion to eliminate the abnormal communication while preserving necessary arterial and venous pathways ESVS Vascular Trauma 2025 · Japanese Guidelines 2017. Dialysis-access fistulas follow a separate intentional-shunt protocol governed by access and maturation goals.

59.6Areas of controversy

The framing of outcomes in high-flow AVM therapy remains debated. Extracranial and peripheral AVM series report substantial rates of recurrence, progression, and incomplete eradication following intervention. Consensus increasingly advises that even aggressive treatment, such as staged ethanol embolotherapy, provides disease and symptom control rather than guaranteed cure Head and Neck AVM 2022 · Extracranial AVM 2025 · Ethanol AVM Cohort 2024.

The incorporation of systemic targeted therapies is evolving. Sirolimus demonstrates efficacy in complex slow-flow vascular malformations, and PIK3CA-directed therapies are used in PIK3CA-related overgrowth spectrum disease. However, the exact indications for transitioning from anatomic procedural care to longitudinal systemic therapy, and the long-term toxicity monitoring required, remain active areas of investigation and specialist refinement Sirolimus Meta-analysis 2025 · VASE Trial 2023 · PIK3CA Targeted Therapy 2018.