Arteriovenous malformations of the extremities

INTRODUCTION — Arteriovenous (AV) malformations are one type of vascular malformation resulting from developmental defects of the arterial and venous vasculature, but without endothelial cell hyperplasia. AV malformations are rare, affecting <1 percent of the population, but they cause significant morbidity over the lifetime of the affected individual [1].

AV malformations can affect any organ, but they most commonly affect the head and neck, with intracranial AV malformations being far more common than extracranial AV malformations [2-6]. Next in frequency are AV malformations of the extremities, which have an equal distribution between the upper and lower extremities [7]. AV malformations have also been reported in trunk and viscera of the chest and abdomen [8,9].

The clinical features, diagnosis, and approach to treating peripheral AV malformations affecting the extremities are reviewed. AV malformations of the central nervous system and the viscera of the trunk and abdomen have unique clinical presentations and treatment approaches and are discussed separately. (See "Brain arteriovenous malformations" and "Pulmonary arteriovenous malformations: Clinical features and diagnostic evaluation in adults".)

CLASSIFICATION AND ETIOLOGY — AV malformations are a rare type of vascular malformation (table 1) resulting from developmental vascular defects. AV malformations comprise 10 to 20 percent of vascular malformations. The true incidence of AV malformations is difficult to determine. Best estimates from the neurologic literature indicate incidental findings at a rate of 1/100,000 [10-12]. The exact etiology is unclear, and there is no sex preponderance or ethnic predilection.

Vascular malformations are classified by whether they shunt blood from high to low pressure (high-flow [fast flow] versus low-flow [slow flow]) and by their various connections. Vascular malformations can include arterial, capillary, lymphatic, or venous elements, or a mixture of these [13]. AV malformations involve the arterial and venous vessels with fistulous connections between them and thus are "high-flow" lesions. It is the high-flow characteristic of AV malformations that makes treatment of these lesions so complex [14]. By comparison, venous malformations are "low-flow" lesions. (See "Venous malformations".)

AV malformation as a term has unfortunately been used as an all-encompassing term, rather than as a term that clearly distinguishes anomalies with arterial and venous elements from those with venous and lymphatic elements, and from vascular tumors. The distinction is important since treatment algorithms differ. (See "Overview of vascular intervention and surgery for vascular anomalies".)

AV malformations have a persistent connection between feeding arteries and draining veins. They are characterized histologically as thick-walled arteries and arterialized thick-walled veins. The connection between the arteries and veins can be direct or indirect and a normal capillary bed is partially or completely absent. AV malformations are thought to occur due to failure in apoptosis of primitive AV shunts during development. Molecular studies have shown a dysfunction in the signaling process regulating proliferation and differentiation, apoptosis, maturation, and adhesion of vascular cells [15].

While AV malformations may be predominantly sporadic, numerous genes are linked to the various vascular malformations. Some studies suggest a "paradominant" inheritance to explain the observed familial transmission [16]. Familial correlations are often difficult to identify, as many malformations are not clinically apparent.

CLINICAL FEATURES

Natural history and progression — AV malformations are present at birth and grow proportionately with the individual; they do not spontaneously regress. AV malformations have a predictable growth pattern consisting of four distinct stages (quiescent, growing, symptomatic, and decompensating). (See 'Clinical staging' below.)

Their tendency to progress leads to a clinical presentation in the second or third decade of life [4]. The spectrum of clinical presentations ranges from minimal to significantly disabling with psychological and emotional impacts. The presentation varies depending on anatomic location, duration, and size of the AV malformation. Compared with other sites that have visible cutaneous manifestations (eg, face, scalp), extremity AV malformations may present earlier. While typically not accompanied by pain, painful lesions have been reported [17].

AV malformations often progress rapidly, increasing the risk for significant morbidity and mortality. As they progress, the increased volume of blood flowing through the lesions causes progressive left-to-right shunting, resulting in increased venous and right-sided heart pressures. Shunting of flow can lead to vascular steal syndromes, but these are more commonly manifested in deeper lesions presenting as ischemia of the structures distal to the lesion. High-output heart failure is rare but can be seen in large, widespread untreated lesions [7]. Bleeding is a common manifestation in longer-standing cutaneous lesions due to venous hypertension, which can lead to stasis changes that are prone to recurrent bleeding with minimal injury and are challenging to control.

AV malformations are thought to expand in response to certain stimuli, such as hormonal changes or trauma [4,18]. Hormonal changes during puberty and pregnancy cause a pro-growth state influenced by growth hormone and vascular endothelial growth factor [18]. Trauma-induced progression can also occur in response to penetrating or blunt force injury, with development of a proinflammatory response and velocity shifts. An iatrogenic influence can also trigger progression following incomplete surgical resection or fistula creation.

Physical findings — When visible on examination, AV malformations of the extremities appear as telangiectasias or macular stains, which can be mistaken for low-flow vascular malformations or infantile hemangiomas. The site of the AV malformation can appear full and engorged. The AV malformations will be slightly compressible, and excess warmth of the skin and palpable pulsations and a thrill will be felt. On auscultation, an audible bruit can be heard.

Long-standing extremity lesions have more pronounced physical features. The vessels beneath the skin may have the appearance of a hemodialysis AV fistula with tightly scarred or thinning skin. The increased venous congestion associated with the AV malformation can result in a similar physical appearance to the extremity as those with longstanding chronic venous insufficiency with dilated veins, and skin changes (edema, stasis dermatitis, ulceration); however, limb elevation will not reduce edema or the mass effect of the AV malformation. Other physical findings may include limb hypertrophy and limb length discrepancy. The contralateral limb and the upper extremities should also be inspected.

Clinical staging — The Schobinger clinical staging system has been used to characterize AV malformations as follows [19,20]:

●Stage I: Quiescence – Asymptomatic, with cutaneous pink-blue blush and skin warmth, shunting detectable with Doppler.

●Stage II: Expansion – Cutaneous blush, lesion enlargement with tortuous veins, pulsation, as well as a bruit or palpable thrill.

●Stage III: Destruction – Pain, dystrophic skin changes, ulceration, skin necrosis, bleeding, distal ischemia, and steal.

●Stage IV: Decompensation – Marked by the above changes and high-output cardiac failure.

DIAGNOSIS — The clinical examination can often suggest the diagnosis and differentiate an AV malformation (high-flow, fast flow) from a venous malformation (low-flow, slow flow). However, vascular imaging is necessary to confirm the clinical diagnosis and identify the extent of the lesion and ensure correct classification of the lesion prior to considering treatment. The evaluation includes determining the type of shunting, thoroughly evaluating the local anatomy, and determining the hemodynamic effects of the AV malformation [4].

Vascular imaging

Ultrasound — When an AV malformation is suspected, ultrasound examination is generally the initial imaging study of choice and can be obtained as a bedside procedure. Doppler ultrasound can quickly differentiate a high-flow (fast flow) from a low-flow (slow flow) lesion. Duplex ultrasound will demonstrate multidirectional flow and high-amplitude arterial waveform with spectral broadening [21,22]. Ultrasound can also be used for periodic re-evaluation of the lesion or for follow-up after treatment [21].

In addition, venous ultrasound examination performed concurrently can identify the presence of reflux in the superficial or deep venous system and the presence of thrombus, and can verify continuity of the deep venous system.

The limitations of ultrasound in the evaluation of AV malformations include poor spatial resolution and the inability to determine the malformation's true extension into muscle and osseous structures. Other limitations are related to the nature of ultrasound, such as operator dependence, the patient's body habitus, and aspects of the transducers and ultrasound machine used.

Magnetic resonance/computed tomographic angiography — Dynamic contrast-enhanced magnetic resonance (MR; time-resolved techniques) provides hemodynamic information as well as the anatomic relationship of the AV malformation to other structures [23]. High-flow lesions are identified by the presence of shunting and fistulous connections, and imaging shows the true extent of the lesion, including soft tissue and musculoskeletal involvement. With software enhancements, the lesion can be isolated and dynamic flow acquisitioned. Dynamic contrast-enhanced MR correctly distinguishes between high-flow (fast flow) and low-flow (slow flow) lesions in 83 percent of patients, with a negative predictive value of 94 percent [23]. While computed tomography is less informative than MR, it may be more useful for evaluating the osseous structures associated with an AV malformation [24,25].

Catheter-based angiography and classification — While many of these lesions can be differentiated with high-resolution MR angiography, catheter-based angiography is often required to classify the AV malformation, which is important to planning treatment.

The Hamburg, International Society for the Study of Vascular Anomalies (ISSVA), and other angiographic classifications have been used to differentiate the various vascular lesions. The more common descriptions of truncular versus extratruncular AV malformation detailed by the Hamburg classification delineate the morphological differences between lesions, which has implications for endovascular treatment.

●Truncular AV malformations involve the main vessel trunks, often a directly communicating artery and vein. These develop in the latter half of embryological development and therefore are less likely to recur after treatment.

●Extratruncular AV malformations are more common and develop early with the vascular system in its reticular stage and are mesodermal tissue remnants with angioblasts in the extremities. This breeding ground or nidus allows for recurrence after treatment.

●Extratruncular AV malformations always have a nidus, whereas it is possible for a truncular AV malformation to have a direct fistulous connection without a nidus [14,26-32].

The International Union of Angiology 2013 classification also incorporates hemodynamic and anatomic characteristics, also differentiating extratruncular and truncular lesions [14].

Further evaluation — If additional information is required to characterize the degree of shunting by an AV malformation, scintigraphy can aid in detecting micro-AV shunting in the soft tissues. In addition, unrecognized lesions can be identified by whole-body blood pool scintigraphy utilizing radioisotope-tagged erythrocytes [33,34].

Other evaluations may be necessary for those with congenital vascular malformations, such as Parkes Weber syndrome [35]. (See 'Syndromes associated with vascular malformations' below.)

Echocardiography — High-output heart failure can occur at any point in time in the presentation of an AV malformation. Several case studies have documented heart failure as the initial presenting symptom in neonates with cerebrovascular AV malformations [36,37].

While there is no established protocol instructing providers when to evaluate for heart failure or right heart strain, echocardiography with a bubble study is recommended at initial presentation for baseline characterization in those with significant shunting, for any patient with a known AV malformation with symptoms of heart failure, as well as for patients who will undergo intervention.

Syndromes associated with vascular malformations — Various genetic mutations can cause syndromes associated with vascular malformations, and these should be considered when evaluating the patient.

Syndromes include:

●Osler-Weber-Rendu syndrome (hereditary hemorrhagic telangiectasia) (See "Clinical manifestations and diagnosis of hereditary hemorrhagic telangiectasia (Osler-Weber-Rendu syndrome)".)

●RASA1 mutations (See "Capillary malformations (port wine birthmarks) and associated syndromes", section on 'Capillary malformation-arteriovenous malformation syndrome'.)

●PTEN mutations (hamartoma tumor syndrome) (See "PTEN hamartoma tumor syndromes, including Cowden syndrome", section on 'Proteus-like syndrome'.)

Fibro-Adipose Vascular Anomaly (FAVA) is a complicated vascular malformation gaining greater recognition, especially after initial therapies have failed or when the patient has had rapid recurrence, often resulting in the hallmark of a painful extremity with contracture, phlebectasia, and fibrofatty infiltration of muscle (image 1). In studies first delineating the radiographic features of FAVA, it was noted to occur preponderantly in females, presenting from birth to 28 years of age, with sites in the extremities (calf, wrist, thigh) more common. Many patients present with pain, limited joint movement, and imaging that demonstrates extra fascial features consisting of dense fibrous tissue, fat, and lymphoplasmacytic aggregates with atrophy of the muscle. Adipose tissue tends to infiltrate the muscle at the periphery of the lesion. Often, large, irregular, and excessively muscularized venous channels and clusters of veins are involved with lymphatic tissue, giving the lesions a "low-flow" lesion appearance [38]. Given the rapid recurrence with traditional treatments for FAVA, alternatives have been sought. Cryoablation has been used, with improvement in pain and physical limitations and skin hyperesthesia in follow-up to five months from intervention [39]. Sirolimus has also been shown to be successful in small case studies, improving pain and quality of life for patients [40].

Some syndromes with vascular malformations may be commonly confused. These include:

●Parkes Weber Syndrome (PWS)

●Klippel-Trenaunay Syndrome (KTS)

●Servelle-Martorell syndrome (SMS)

While all can look similar, PWS has the fistulous connections associated with AV malformations, while KTS is always a low-flow lesion (ie, venous malformation). Both can have port-wine stains (capillary malformations), limb length discrepancies, and edema. Another defining characteristic of KTS is the presence of a lateral thigh draining vein that is often present from birth, and which can be ligated or ablated in most patients. SMS differs from both PWS and KTS, which have osseous hypertrophy and limb lengthening. By contrast, SMS has bony hypotrophy and hypoplasia with limb shortening. In addition, grotesque limb distortion and unusually numerous radiographic phleboliths are more likely to complicate SMS. High-flow AV malformations are typically absent in SMS and, when present, suggest the diagnosis of PWS [41].

DIFFERENTIAL DIAGNOSIS — The differential diagnosis of AV malformations predominantly includes other types of vascular malformation and vascular tumors.

Other types of acquired fistulous arteriovenous pathologies (eg, iatrogenic, traumatic AV fistula), are usually evident from the patient's history. Chronic venous disease is more typically symmetric and often bilateral. (See "Acquired arteriovenous fistula of the lower extremity" and "Overview of lower extremity chronic venous disease".)

Other vascular malformations — Vascular malformations are often confusing to classify and are commonly initially misdiagnosed.

Capillary malformations — Capillary malformations, such as diffuse capillary malformation with overgrowth (DCMO), are confusing to many providers, especially in the setting of large ropy varicosities that can be present and the sheer mass effect that can be seen with these. Nearly 90 percent of capillary malformations (ie, port-wine stains) are found on the face and are sometimes seen with other syndromes (eg, Sturge-Weber syndrome; Klippel-Trenaunay Syndrome; Capillary malformation of the lower lip, Lymphatic malformations of the face and neck, Asymmetry, and Partial or generalized Overgrowth [CLAPO] syndrome). They are often flat erythematous patches and can thicken or bleed over time. Patients can present with axial and circumferential soft tissue and bony overgrowth leading to limb length discrepancy. On physical examination, there are no thrills or bruits, and on vascular imaging, there are no fistulous connections, lymphatic overgrowths, and no intramuscular or venous malformations. (See "Capillary malformations (port wine birthmarks) and associated syndromes".)

Venous/lymphatic malformations — Venous malformations are "low-flow" lesions. These may incorporate lymphatic tissue and are often seen in many of the combined malformations, such as Klippel-Trenaunay syndrome. (See "Venous malformations".)

Low-flow lesions can present like AV malformations but are often slower to progress. The patient can have a similar warmth, mass, port-wine stain, or limb discrepancy. A large "bird's nest" deformity of the veins is common. Venous and lymphatic malformations can be disfiguring and painful due to the mass effect or related cellulitis or phlebolith formation. However, the characteristic palpable thrill and bruit seen with the AV malformations is absent [2].

Whereas both AV malformations and lymphatic malformations can remain engorged with limb elevation, with lymphatic malformations, ultrasound will demonstrate large lymphatic pools in the tissue free from color flow and arterial involvement.

Vascular tumors — Compared with vascular tumors (eg, hemangiomas, kaposiform hemangioendotheliomas, pyogenic granulomas), vascular malformations, including AV malformations, have a normal cellular turnover without increased endothelial proliferation. (See "Overview of vascular intervention and surgery for vascular anomalies".)

Hemangiomas are benign vascular tumors. They are spongy and blanch with pressure, but bleeding is uncommon. Hemangiomas can often be distinguished from AV malformations and other vascular malformations by location. Hemangiomas are more commonly found on the head and neck (60 percent of the time) and at a single location. Hemangiomas have a distinct pattern of growth with a rapid proliferation in the first year of life, while vascular malformations are more measured and grow with the body [42]. Unlike vascular malformations, infantile hemangiomas spontaneously regress over several years [43]. Nearly all hemangiomas resolve by age 10 [44]. (See "Infantile hemangiomas: Epidemiology, pathogenesis, clinical features, and complications".)

Congenital hemangiomas are fully grown at birth and do not exhibit the typical postnatal proliferation. Congenital hemangiomas are less likely to involve the head and neck and rarely ulcerate [42,45,46]. Two main forms exist, the rapidly involuting congenital hemangioma (RICH) and the non-involuting congenital hemangioma (NICH), which does not regress. A well-circumscribed hypervascular mass seen on ultrasound with low-resistance waveforms often can confirm clinical diagnosis. (See "Congenital hemangiomas: Rapidly involuting congenital hemangioma (RICH), noninvoluting congenital hemangioma (NICH), and partially involuting congenital hemangioma (PICH)".)

Other vascular tumors include pyogenic granuloma and Kaposiform hemangioendothelioma. The clinical characteristics of these vascular tumors are reviewed separately. (See "Pyogenic granuloma (lobular capillary hemangioma)" and "Tufted angioma, kaposiform hemangioendothelioma (KHE), and Kasabach-Merritt phenomenon (KMP)".)

APPROACH TO TREATMENT — The best opportunity for improved quality-of-life for patients with AV malformations is early diagnosis and management using a combination of conservative, endovascular, and surgical treatments provided by a multidisciplinary team. Obstacles and misconceptions remain about the treatment of vascular malformations, in general, including AV malformations, most likely related to incomplete knowledge and unfounded fears concerning these lesions.

While there is a lack of both uniform reporting standards and definitive assessments of the available treatments due to the rarity of these lesions, there is an emerging consensus that a multidisciplinary team is necessary to properly diagnose and coordinate care among disciplines when dealing with these complex cases. The multidisciplinary team may include specialists from vascular, plastic, otolaryngologic, orthopedic, or pediatric surgery; radiology (diagnostic, interventional); dermatology; and hematology. Each patient's treatment should be individualized to provide the most positive result [22,47]. Treatments must prioritize care for vital structures in treatment and monitoring for progression while balancing potential disfigurement and social stigmatization that is an obvious concern for the patient.

●Asymptomatic patients with isolated extremity AV malformations can be safely observed. Close follow-up and multidisciplinary team management is suggested, with extensive patient education. (See 'Conservative management' below.)

●Treatment of symptomatic lesions often requires vascular intervention or surgery. The goal of treating AV malformations is control of AV shunting to reduce the clinical manifestations. For AV malformations with favorable angiographic features and AV fistulas, cure is often possible. However, for diffuse AV malformations, staged procedures may be needed to limit tissue damage [4]. Incomplete therapy should be avoided, since it typically leads to recruitment of more vessels, collateralization, and expansion of the AV malformation. (See 'Vascular intervention and surgery' below.)

Conservative management — Conservative management can be a short- or long-term treatment strategy based on the patient's symptoms, risks to the limb, and functional imitations and includes extremity compression, medications, physical therapy, and ongoing clinical monitoring. Conservative management is the mainstay of treatment for asymptomatic isolated extremity AV malformations. For those in whom the risk of intervention outweighs the benefit or interventions have provided maximum effectiveness, conservative measures may also help control symptoms.

Compression therapy — For patients with newly diagnosed AV malformations, we prescribe compression garments (20 to 30 mmHg, 30 to 40 mmHg) to reduce swelling and/or symptoms [14]. A custom garment is often required to achieve a proper fit, particularly in pediatric patients. Additional information regarding application and care of compression garment is provided separately in the context of chronic venous disease, but the principles of use are similar. (See "Compression therapy for the treatment of chronic venous insufficiency".)

Medications — Medical management of AV malformations may include pain management (eg, nonsteroidal anti-inflammatory drugs) and antithrombotic therapy. Other therapies (eg, sirolimus) have been used effectively to treat vascular tumors and complicated vascular malformations in patients who lack treatment options [48-50].

Intermittent measurement of D-dimer is useful for determining if the patient has localized intravascular coagulopathy (LIC). LIC is relatively common in low-flow lesions, but it can also occur with high-flow lesions. For patients identified with LIC, anticoagulation can reduce the risk of progression to disseminated intravascular coagulopathy [51]. Dosing varies, ranging from prophylactic to full anticoagulation dosing. Low-molecular-weight heparin (LMWH) 40 mg daily, apixaban 5 mg daily, and rivaroxaban 10 mg daily are the most common agents and doses used prophylactically. In the pediatric population, LMWH and warfarin are favored over the newer Xa inhibitors, primarily out of dosing concerns. It is imperative to involve a hematologist when managing pediatric patients.

Vascular intervention and surgery — Intervention for AV malformations may include a combination of transarterial catheter-based embolization, surgical resection, and transcutaneous sclerotherapy (once communication between the arterial source and the nidus has been eliminated).

Endovascular treatments have emerged as the standard of care, but no endovascular embolization agent or device has been demonstrated to be superior to any other. Elimination of arterial flow can be performed with microparticles, coils, liquid embolic agents, or plugs, alone or in combination, and the agents chosen are determined by the anatomy of the arteriovenous connections.

Prior to engaging in any endovascular intervention, identifying the anatomic characteristics of the malformation and "true nidus" are critical. Researchers have described this angioarchitecture and provided several classification systems [52,53]. One of these authors expanded upon many of these classification systems and even provided guidelines for potential curative treatment strategies that can be used for each lesion type.

Coil embolization is effective if there are very few points of direct communication between the arterial and venous sides and if the vascular channels are large enough to be treated in this manner. Coils or plugs are never placed in an arterial vessel feeding a nidus, because this eliminates future access to the lesion, creates recruitment of additional vessels to the lesion, and is ineffective in reducing lesion size.

The outcomes of surgical resection of the AV malformation have improved with the preoperative embolization techniques by reducing bleeding and localizing the lesion [54]. Endovascular treatments can also be used post-excision to manage any residual malformation.

AV malformations are often poorly localized, making complete resection difficult, and the residual mass can result in reformation of additional lesions. Treatment of extensive or combined lesions is frequently palliative and goal-oriented and may need to be repeated over time to control the lesion. The decision for excision must be made by a multidisciplinary team and with a surgical specialist directly communicating with the interventionalist in the correct timing of excision. The need for tissue expanders, skin grafts, and the potential for nerve damage following en bloc resection must be addressed. Because wide excision can produce a less-than-desirable cosmetic or functional effect, ongoing endovascular treatments can be considered for large lesions as a palliative measure to possibly avoid surgical resection altogether. (See "Overview of vascular intervention and surgery for vascular anomalies", section on 'Arteriovenous malformation'.)

For patients identified with superficial venous reflux, superficial venous ablation may improve residual symptoms that may be present following treatment of the AV malformation. Venous ablation procedures are discussed in detail separately. (See "Approach to treating symptomatic superficial venous insufficiency", section on 'Candidates for venous intervention'.)

OUTCOMES — AV malformations are rare, with a variety of clinical courses, which contributes to differences in reported outcomes of treatment. Vascular malformations, including AV malformations, can be effectively treated, but they are rarely cured. The nidus and surrounding peripheral vessels and tissues can be treated to eliminate symptoms, but recurrence is always a possibility. Thus, it is important to convey that the management of the AV malformation is lifelong and requires ongoing monitoring. It is common for a patient to have periodic treatments throughout their lifetime.

SUMMARY AND RECOMMENDATIONS

●Arteriovenous malformations – Arteriovenous (AV) malformations are rare genetic anomalies of the vasculature resulting from developmental defects of arterial and venous origins, but without endothelial cell hyperplasia. AV malformations involve fistulous connections between arterial and venous vessels and as such are high-flow (fast flow) lesions. AV malformations commonly affect the head and neck, followed by the upper or lower extremities, but they can affect any organ (eg, lung, viscera). (See 'Introduction' above and 'Classification and etiology' above.)

●Clinical features – AV malformations are present at birth and grow proportionally with the individual, typically presenting in the second or third decade. The clinical features of AV malformations depend upon their duration, anatomic location, and size. On examination, a palpable pulsation and thrill will be felt overlying the lesion, and on auscultation, an audible bruit can be heard. AV malformations progress through four distinct stages (asymptomatic [quiescent], growth, symptomatic, decompensation). As the volume of blood flowing through the lesion progressively increases, left-to-right shunting worsens and can result in vascular steal syndromes or heart failure. (See 'Clinical features' above.)

●Diagnosis – The clinical examination suggests the diagnosis and can often differentiate a high-flow (fast flow) lesion (ie, AV malformation) from a low-flow (slow flow) lesion (eg, venous malformation), but vascular imaging is necessary to confirm the clinical diagnosis.

•The initial diagnostic imaging study is duplex ultrasound. Concurrent venous duplex examination should also be performed to evaluate for venous thrombosis and reflux. (See 'Ultrasound' above.)

•Dynamic contrast-enhanced magnetic resonance (MR) angiography provides hemodynamic information distinguishing AV malformations from venous malformations, as well as the anatomic relationship of the AV malformation to surrounding structures. Computed tomography (CT) angiography may be more useful for evaluating nearby osseous structures associated with an AV malformation. Prior to intervention, catheter-based angiography is necessary to further classify the AV malformation as truncular versus extratruncular, which impacts treatment. (See 'Vascular imaging' above.)

●Differential diagnosis – The differential diagnosis of AV malformation includes primarily other vascular tumors and vascular malformations. (See 'Differential diagnosis' above.)

●Management – Management of AV malformations involves a combination of conservative, endovascular, and surgical treatments provided by a multidisciplinary team. AV malformations can be effectively treated, but they are rarely cured, and lifelong monitoring is required. (See 'Approach to Treatment' above and 'Outcomes' above.)

•Asymptomatic – Asymptomatic patients with isolated extremity malformations can be safely observed with close follow-up and patient education. Conservative management includes extremity compression, physical therapy, possibly anticoagulation, and ongoing clinical monitoring of the extremity.

•Symptomatic – Treatment of symptomatic lesions may include a combination of transarterial catheter-based embolization, transcutaneous sclerotherapy (once communication between the arterial source and the nidus has been eliminated), or surgery. The goal of treatment is control of AV shunting to reduce symptoms. For complex or diffuse AV malformations, treatment is frequently palliative and goal-oriented and may need to be repeated throughout the patient's lifetime to control the lesion. Staging procedures may help to limit tissue damage.