Surgery for Congenital Arterial and Venous Anomalies 

Vascular anomalies are encountered infrequently in everyday practice. These lesions represent a heterogeneous group of isolated or multiple abnormalities that are sometimes associated with complex congenital syndromes. Most vascular anomalies affect the skin, although any organ system can be involved. Importantly, nearly all cutaneous congenital vascular abnormalities are evident either at birth or within the first few weeks of life.

A great deal of confusion surrounds the nomenclature and classification of congenital vascular abnormalities. Alarmingly, as reported in one study, up to half of patients referred to specialty clinics for vascular abnormalities had been diagnosed and monitored incorrectly.^[1] As put forth by Mulliken and colleagues, an appropriate start to any discussion of congenital vascular abnormalities should include the distinction between vascular tumors (eg, hemangiomas) and vascular malformations (eg, capillary or lymphatic), as the two entities are decidedly different.

Whereas vascular malformations result from abnormal embryogenesis and/or early fetal life, vascular tumors are endothelial neoplasms characterized by cellular proliferation and growth. Malformations may involve a single type of vessel (eg, capillary or lymphatic) or be of mixed variety (see outline below). In clinical practice, malformations are designated by the predominant channel type and resultant rheologic character (ie, fast vs slow flow).

Vascular tumors encompass a broad range of lesions, including angiosarcomas and tufted angiomas, among others. However, the most common vascular tumor remains the hemangioma, a begin lesion usually found in infants.

Currently, various schemas are used to categorize vascular tumors and malformations,^{[2, 3]} stemming from the original classification described by Mulliken and Glowacki.^[4] The Mulliken and Glowacki classification is based on the pathological characteristics of the endothelium and natural course of the lesion. A simplified outline of their original classification of vascular anomalies is as follows:^[5]

Tumors include the following:

• Hemangioma
• Pyogenic granuloma
• Kaposiform hemangioendothelioma
• Other rare tumors

Malformations include the following:

• Capillary
• Lymphatic
• Venous
• Arteriovenous
• Combined

The topic of vascular anomalies is quite broad. This article serves as superficial review covering the major tumors and malformations that the general surgeon and/or practitioner may encounter. In order to minimize confusing nomenclature and to organize the discussion of the topic, this article adheres to the Mulliken/Glowacki schema outlined above.

Finally, it deserves mention that many vascular anomalies are found in association with syndromes. A full discussion of such syndromes is outside the scope of this article, but a brief litany of predominant syndromes is mentioned in Clinical.

Embryological studies by Woodward et al at the turn of the 20th century shed light on the understanding of vascular congenital anomalies.^[6]

As a whole, vascular anomalies comprise a very heterogeneous group of disease processes and remain plagued by confusing terminology. Hence, prompt proper diagnosis and appropriate treatment for patients often remains lacking. Moreover, the presence of such lesions at birth and early childhood invokes concern and fear in parents and, in some cases, starts a protracted process of multiple visits to various specialists. Thus, it is mandatory to take the time and diagnose lesions appropriately early on and to ensure that a multidisciplinary team approach be used if the disease process warrants. The first step toward this goal is to obtain a careful history and physical examination, as these can distinguish between vascular tumors and malformations with a diagnostic accuracy exceeding 90%.^[7]

Frequency

In general, vascular anomalies are rare, and limited data exist as to the true worldwide incidence and prevalence. However, there is now a growing body of observations detailing the epidemiology and natural history of the more common subtypes of the anomalies (eg, hemangiomas, venous malformations).

Hemangiomas are the most common tumors of infancy and childhood, observed in 4%-12% of infants during the first year of life.^{[8, 9]} They are 3-5 times more common in females than in males. They are also more common in premature infants, with the risk increasing with lower birth weight.^[10] The incidence among nonwhite populations remains unknown; however, hemangiomas in dark-skinned individuals are uncommon.^[5]

Epidemiologic data regarding vascular malformations are also scarce. The overall incidence of congenital vascular malformations in the general population is estimated at 1.5%. Approximately two thirds of malformations are of venous predominance and are evenly distributed according to sex and race.^[11] In two separate case series, for example, patients with congenital vascular malformations were evaluated at Children's Hospital of Mexico City (1963-1983; 223 children) and the Walter Reed Army and National Naval Medical Centers (1984-1998; 169 children). Of the 392 patients, 257 (65.6%) had malformations of venous predominance. Prevalences of phlebectasia, aplasia or hypoplasia of venous trunks, aneurysms, and avalvulia were also recorded.

As described above, the etiology of a particular vascular anomaly varies greatly depending on the nature of the lesion. In general, vascular tumors are endothelial neoplasms, the molecular biology of which remains poorly understood and characterized. Recently, there has been much interest in the mechanisms underlying the formation of hemangiomas, as these are the most common of vascular tumors. Although data from animal models remain lacking, research performed with human tissues has implicated numerous signal pathways that are altered during the various phases of hemangioma development. These include bFGF, VEGF, TIMP1, and HIF, among others.^[12] However, apart from these observational data, the mechanistic understanding of hemangioma development remains poor. Although some authors have suggested a hereditary component to hemangiomas, the data supporting this notion remain conflicted.^[13]

Vascular malformations are speculated to arise from abnormalities in the process of normal vascular development. Specifically, perturbation of early angiogenesis and vasculogenesis may result in abnormal vascular channels, leading to the formation of vascular malformations.^[14] In contrast with vascular tumors, vascular malformations seem to have a strong hereditary component, with specific lesions observed in the setting of inherited syndromes. Recently, alterations in several signaling molecules and pathways have been identified in specific types of malformations. For example, TIE2,^[15] glomus cells,^[16] and basic fibroblast growth factor (bFGF)^[5] have all been implicated in the formation of arteriovenous malformations (AVMs). Investigators have localized chromosomal mutations underlying several combined vascular formation syndromes (eg, Klippel-Trenaunay, Proteus), further supporting a hereditary component to the development of AVMs.^{[17, 18]}

Hemangiomas

Hemangiomas appear in the first few weeks of life, as opposed to vascular malformations, which are always present at birth, although not always readily apparent. The natural course of hemangiomas is one of spontaneous regression, with only one rare variant that may persist unchanged through an individual’s life.^[19] Conversely, vascular malformations never regress and often grow over time. Hence, as a rule, vascular lesions that persist into adolescence and adulthood are true vascular malformations and should not be referred to as hemangiomas.

Hemangiomas typically have 3 stages classified by clinical assessment, microscopic morphology, and immunohistochemical markers: proliferation phase (age 0-1 years), involuting phase (age 1-5 years), and involuted phase (>5 years).^[20] Most hemangiomas are small and pose only minor clinical problems before they involute and become clinically silent. However, about 20% pose significant problems and require treatment.^[21] This may result from aggressive growth, proximity to vital structures, or complications such as ulceration, bleeding, or even high output cardiac failure.^[22] Finally, the disfiguring nature of certain lesions may prompt parents to seek intervention early, as opposed to waiting for the involution phase.

Vascular malformations

The pathophysiologic characteristics of vascular malformations are dictated by the type of channels involved (heme vs lymphatic) and the flow characteristics of the resultant lesion. Typically, capillary, venous, and lymphatic lesions tend to be slow-flow, whereas arterial lesions are fast-flowing. Any combination of these elements is possible, resulting in an AVM, capillary-lymphaticovenous malformation (CLVM), or lymphaticovenous malformation (LVM). The pathophysiology of specific malformations is discussed in Clinical.

Hemangiomas

These lesions are usually noted in the first 2 weeks of life, although the exact timing depends on multiple factors, including the location of the lesion. Most start as a small cutaneous mark that resembles a bruise or red macular lesion before progressing to a more prominent lesion. Most hemangiomas (60%-80%) develop on the craniofacial region, followed by the trunk and extremities. While most cutaneous lesions are isolated, approximately 20% are multiple. Such multiple lesions should alert the clinician to the possibility of visceral organ involvement, as is often the case.^[21]

The presentation and course of hemangiomas is quite variable, depending on the location and depth of the lesion itself. For example, deeper cutaneous lesions may not possess a typical “strawberry” appearance but may instead appear darker with a bluish hue. During the proliferating phase, frequent assessment and documentation of the lesion is necessary, as progression of the lesions is unpredictable. A small lesion may rapidly blossom into a very large one or take a much less aggressive course. Usually, lesions plateau by age 1 year, marking the end of the proliferation phase.

During the next clinical phase (involuting), the growth of the lesion slows and parallels the growth rate of the child. As the lesion matures and begins to regress, it usually lightens in color, often adopting a grayish hue, and becomes softer to palpation. By age 5-7 years, the final traces of color usually disappear, leaving either very little evidence of the lesion or an atrophic fibrofatty patch with telangiectatic vessels. In approximately 50% of children, the site of the lesion matures to a normal texture and consistency. However, it is not presently possible to predict the course a particular lesion may take, as no reliable clinical factors predict final cosmetic outcome. In general, facial hemangiomas may lead to long-term cosmetic defects, as the lesion might destroy hair follicles and may produce mass effects on the facial skeleton, nose, and/or jaw.^[5] Hemangiomas complicated by chronic ulceration may also leave prominent scars.

As described above, most hemangiomas resolve without serious long-term complications and require only appropriate diagnosis and expectant management. However, approximately 20% of lesions become clinically significant and require more in-depth workup and treatment.^[21] Specifically, lesions that involve the head and neck deserve particular attention. Dermatomally distributed facial lesions, in particular, may indicate the presence of PHACES syndrome (posterior fossa malformations, hemangiomas, arterial anomalies, coarctation of the aorta and cardiac defects, and eye anomalies). These warrant multiorgan evaluation and radiographic evaluation (facial MRI).^[23] Similarly, the presence of numerous hemangiomas (so-called “disseminated hemangiomas”) may indicate the presence of visceral lesions involving the liver, lung, GI tract, or brain. Screening with ultrasonography or MRI should be considered in these patients.

Other lesions that warrant early attention are those that involve the airway (usually heralded by a cutaneous cervical lesion), those that involve the eye and related structures, and those in the lumbosacral region. In neonates with these lesions, prompt evaluation by appropriate specialists (pediatric surgeon/ophthalmologist) should be sought, as therapeutic interventions (eg, tracheostomy) may be required. In the setting of lumbosacral disease, ultrasonography and/or MRI might be indicated to rule out underlying spinal cord defects.

One of the more problematic complications of cutaneous hemangiomas remains ulceration of the skin, affecting approximately 5% of infants.^[24] Ulceration most commonly arises in lesions that involve the extremities, lips, and perineum. Most ulcerative lesions can be treated with local wound care. Laser treatment and even resection may be considered if the ulceration is extensive.

While most vascular tumors encountered in clinical practice are hemangiomas, other, rarer lesions such as pyogenic granuloma and kaposiform hemangioendothelioma should also be considered when a vascular lesion in the neonate is evaluated. Although such tumors are rare, it is essential that they be diagnosed early, as treatment of the lesion and possible associated syndromes (eg, Kasabach-Merritt) may be required.

Venous malformations

Venous malformations, which remain the most common form of vascular malformation, are composed of thin-walled, endothelial-lined, dilated, spongelike channels. Smooth muscle is notable absent. Venous malformations are usually blue-gray in color, are compressible, and grow slowly over time (usually growing as the child grows). The lesions may be small and varicose or large and extensive, involving the extremities, face, or trunk. Visceral involvement may also occur. Cutaneous lesions may visibly expand upon a Valsalva maneuver, a property that may aid in diagnosis during physical examination.

Phlebothrombosis is a common complication of venous malformations, resulting in pain, swelling, and stiffness of joints and muscles. The location and size of a specific lesion dictate the extent of clinical pathology. In general, the mass effect of a growing lesion leads to local symptoms. For example, craniofacial lesions may cause obstructive ocular and aerodigestive complications such as exophthalmia and sleep apnea, respectively. Lesions in the skin and soft tissue may cause extensive disfigurement. Deeper lesions that involve muscle or bone may eventually lead to a loss of musculoskeletal function and even pathologic fractures due to bony destruction.

Workup of venous malformations should include coagulation studies, as extensive venous malformations have been associated with coagulopathies. MRI and/or venography may also be required to determine the extent of involvement of a venous malformation. Indications for treatment of these lesions include cosmetic disfigurement, pain, and functional impairment. The mainstay of therapy remains a combination of compression, sclerotherapy, and surgical resection.

Capillary malformations

Capillary malformations (also known as port-wine stains) can occur anywhere on the body, with a prevalence of 0.3% at birth.^[25] These lesions often manifest as discolorations of the neonatal skin and may darken over time, accompanied by a nodular expansion. Capillary malformations on the face may follow a dermatomal distribution, although more than half cross dermatomes or occur bilaterally.^[26] Lesions may involve the mucosal membranes and may cause significant distortion of the face with bony overgrowth and gingival hyperplasia.

The presence of capillary malformations should alert the physician to the possibility of anatomically associated central nervous system defects, such as ectopic meninges, arteriovenous malformations of the spinal cord (Cobb syndrome), lipomeningocele, tethered cord, or spinal dysraphism. Lumbosacral lesions may also be accompanied by spinal cord abnormalities and neurological bladder dysfunction.^{[27, 28]}

Sturge-Weber syndrome must be considered in the presence of facial capillary malformations. This syndrome is characterized by facial capillary malformations and ipsilateral ocular and leptomeningeal vascular anomalies.^[26] Leptomeningeal vascular anomalies may be of venous, capillary, or mixed types and can cause various neurological symptoms such as seizures and hemiplegia. Choroidal anomalies are also often present, necessitating frequent ophthalmologic evaluation.

Lymphatic malformations

Lymphatic malformations are usually noted at birth or within the first few years of life and may manifest in numerous forms. These lesions may be isolated, may encompass a large anatomical area, and may involve multiple organs. The classification of these lesions is based on radiologic and histologic evaluation and resultant grouping into microcytic, macrocytic, and combined forms. Although the terms lymphangiomas and cystic hygromas have historically been used to describe these lesions, they are considered to be dated and are no longer condoned by experts in the field.^[5]

Lymphatic malformations may occur in any location but are typically found in the cervicofacial region, mediastinum, chest, axilla, perineum, buttock, and retroperineum.^[29] The lesions can range from small spongelike blemishes to large bulky masses that cause severe disfigurement. The overlying skin may appear normal, may exhibit bluish discoloration, or, in the case of dermal involvement, may be riddled with tiny dark-red vesicles caused by intravesicular bleeding. A significant complication of lymphatic malformations remains intralesion hemorrhage, which can affect up to 13% of cases.^[30] This is often heralded by rapid growth of the lesion, predisposing the area to infection. If bleeding occurs, antibiotic therapy should be started immediately.^[5] However, prophylactic treatment with antibiotics is not presently recommended.

Notably, faciocervical lymphatic malformations may result in significant ophthalmologic symptoms, dental problems, and/or airway compromise, the latter possibly necessitating tracheostomy.^{[8, 31]}

The management of lymphatic malformations centers on the prevention of bleeding, infection, and mass-effect. The mainstays of treatment are sclerotherapy and surgical excision.

Arteriovenous malformations

Arteriovenous malformations (AVMs) are usually diagnosed at birth and may be mistaken for other types of malformations (eg, capillary malformations). As their name implies, AVMs consist of arteriovenous structures that allow shunting to occur. The lesions are defined by the presence of feeding and draining vessels. Consequently, the natural history of the lesion is one of progression.^[32]

AVMs may first be evident as small discolored areas on the skin and progress at different rates depending on the nature of their flow (ie, fast vs slow). Fast-flow lesions typically evolve quickly, resulting in worsening erythema, rubor, bruits, and thrills. Trauma may exacerbate the lesions, and rapid growth may be observed during puberty.^[5] As the arteriovenous shunting worsens, local ischemic signs may manifest (ulceration, pain, bleeding). Extensive lesions may lead to high-output cardiac failure as the heart attempts to maintain perfusion in the presence of a large arteriovenous shunt.

Schobinger summarized the natural history of congenital AVMs as evolving through 4 distinct clinical stages, as follows:^[33]

1. Quiescence - Characterized by a pink violaceous mark and the presence of an arteriovenous shunt detectable by echo-Doppler ultrasonography
2. Expansion - As in stage 1, but clinically pulsatile, with obvious presence of tortuous vessels
3. Destruction - As in stage 2, along with damage to surrounding tissue (eg, dystrophic skin changes), ulceration, bleeding, and continuous pain
4. Decompensation - Similar to stage 3, but associated with cardiac failure due to voluminous shunting

AVMs can occur almost anywhere in the body. An intracranial location is most common, followed by the head, neck, extremities (lower more so than upper), trunk, and viscera. Among AVMs that involve the extremities, those associated with fistulous shunts of the femoral vessels are most common. Many investigators choose to reserve the term "atriovenous fistula" for the acquired traumatic variant comprising a solitary fistula. Patients with an AVM involving the brain may have a dramatic presentation, including neurological symptoms. Pelvic AVMs are usually extensive and manifest as vaginal bleeding or symptoms related to compression of other pelvic organs. Congenital visceral fistulas can involve the lung, kidney, and alimentary tract. Alimentary tract AVMs are usually part of congenital telangiectatic syndromes and often present with a GI bleeding.

Multimodality imaging with ultrasonography (Doppler), MRI, and angiography may be required to fully characterize a lesion. As many AVMS are not localized and infiltrate deeply into several tissue planes, such imaging may be necessary to determine the best course of treatment.^[34] Treatment is individualized on a case-by-case basis, taking into consideration the location and extent of the lesion. A multidisciplinary approach is often required, with embolization, sclerotherapy, and surgical resection being the mainstays of treatment.

Combined malformations

Lesions with multiple combinations of vascular elements are grouped into this category. So called capillary-lymphaticovenous malformations (seen in Klippel-Trenaunay syndrome) often involve the extremities, resulting in disfiguring hypertrophy of the involved limb. Functionality of the limb may also be affected, requiring surgical debulking, if appropriate. Other combined malformations include those that manifest in individuals with Parkes-Weber syndrome. Limbs are typically affected and exhibit enlargement with skin changes. Treatment may include expectant management and embolization, if appropriate.

As the nature of vascular anomalies is quite diverse and encompasses many types of lesions, indications for treatment are nuanced and variable. In general, the decision to intervene should take into consideration the type of lesion, associated symptomology, and desires of the patient and family.

Hemangiomas

Most hemangiomas are small tumors that eventually undergo involution. However, treatment may be warranted if the tumor is large, grows rapidly, is complicated by severe ulceration, is in a threatening location, or might otherwise cause complications.

Venous malformations

Indications for treatment of these lesions include appearance, impairment of function, and protracted pain.

Capillary malformations

Capillary malformations are largely treated for cosmetic reasons; however, excision may be warranted in patients who develop fibronodular hypertrophy or who have extensive facial involvement.

Lymphatic malformations

Treatment of these lesions should be geared toward preventing infection and bleeding, correcting cosmetic deformity, and improving function of affected areas.

Arteriovenous malformations

Quiescent AVMs may be managed expectantly; however, pain, bleeding, ulceration, and extensive enlargement are all indications for treatment. Symptomatic lesions that are not amenable to surgical treatment may be considered for palliative embolization therapy.

Combined malformations

Treatment is indicated to mitigate the sequelae of these lesions, including hypertrophy, lymphatic weeping, pain, and loss of functionality.

See Clinical.