Sonography of abdominal wall vascular malformation: a case report and review of the literature

Vascular anomalies are classified as vascular tumors (VT) and vascular malformations (VM). VTs are divided according to their clinical behavior, while VMs are classified according to their flow characteristics, histopathologic features, and associations with other anomalies. Sonography emerges as the diagnostic imaging method of first choice for assessing abdominal wall disorders and masses, thus representing a valuable tool for the diagnosis and follow-up of abdominal wall VMs. In this review, we report a case of abdominal wall arteriovenous malformation (AVM) in a 17-year old and briefly discuss the cases of abdominal wall VMs.

Abdominal wall mass, Sonography, Vascular malformation

Vascular anomalies are classified as vascular tumors (VTs) and vascular malformations (VMs). VTs are divided according to their clinical behavior, while VMs are classified according to their flow characteristics, histopathologic features, and associations with other anomalies. VMs can occur in various sites, such as visceral organs as well as the respiratory and gastrointestinal tracts, but they are commonly located intracranially [1, 2]. Any blood vessel type or a combination thereof may be affected by a VM. These lesions can infiltrate normal tissue, which makes them very difficult to manage. The most common VMs include lymphatic malformations, capillary-venular malformations, venous malformations, and arteriovenous malformations (AVMs). While different in their biologic and clinical profiles, as a whole, VMs do not regress and continue to expand with time. Periods of rapid growth, infiltration, and soft tissue destruction will spur therapeutic approaches that depend upon the malformation involved [3]. We report a case of abdominal wall AVM in a 17-year old female located in the left lower abdomen wall, detected by sonography and treated by embolization. Four years following the embolization, at the ultrasound (US) evaluation, the mass appeared slightly reduced in size, with less represented intralesional flows and reduced perfusion upon color-power Doppler analysis. Furthermore, we performed a systematic literature search in PubMed and included case reports and articles in the English language dealing with sonographic descriptions of abdominal wall VM and related disorders. Case description A 17-year old female patient came to our observation at the Ultrasound Diagnostics Department because of painless swelling in the lower abdomen wall (Fig. 1a). A large mass was observed in the left hipogastric region during the physical examination; it was not mobile with respect to the underlying soft tissues, with parenchymatous consistency at the palpation. The US examination, performed with linear and convex multi-frequency probes, showed that the lump was characterized by an oval morphology, lobulated margins, and a nonhomogeneous internal echo-structure. The mass was located below the subcutaneous tissue, protruding deeply toward the anterior bladder wall (without infiltrating it) (Fig. 1b, c). Color-power Doppler analysis showed an intense intralesional vascularization with a large number of vessels; in particular, it showed a hypertrophic artery with high perfusion (Fig. 1d). Magnetic resonance angiography (MRA) confirmed the presence of a voluminous expansive mass (craniocaudal diameter: 14.07 cm; anteroposterior diameter: 5.13 cm) characterized by hyperintensity in T2-weighted sequences and isointensity concerning soft tissues in T1 sequences as well as intense and nonhomogeneous contrastographic impregnation and intralesional vascular structures (Fig. 1e). The mass was fed by the left inferior epigastric artery. Furthermore, the mass protruded into the abdominal cavity with close anatomical relations of continuity with the anterior wall of the bladder, the anterior wall of the uterine fundus, and the sigma. The radiological findings described were compatible with a neoformation originating in the muscles of the abdominal wall. A histological evaluation was performed after a US-guided excisional biopsy of the larger mass, thereby confirming the sonographic suspicion of an intramuscular AVM. The size of the mass, its complex anatomical position, and the clinical findings (i.e., asymptomatic patient) caused the multidisciplinary team to opt for serial embolizations coupled with a strict ultrasonographic follow-up. Four years following the embolization treatments, at the US evaluation and through a panoramic view, the mass appeared slightly reduced in size (craniocaudal diameter: 9.72 cm; anteroposterior diameter: 4.16 cm), with less represented intralesional flows and reduced perfusion upon color-power Doppler analysis (Fig. 2).

In 1982, Mulliken and Glowacki created the first classification based on the normal development, cellular kinetics, and histopathology of vascular abnormalities [4]. Endothelial malformations are biologically classified into two major groups: hemangiomas and VMs. Hemangiomas are benign vascular neoplasms characterized by an increased cycle of endothelia, mast cells, fibroblasts, and macrophages. On the other hand, VMs are not tumors, but rather, they develop according to developmental defects in vascular morphogenesis, which occur during the normal endothelial development cycle [4]. In 1996, in Rome, the International Society for the Study of Vascular Anomalies (ISSVA) classified vascular anomalies into two groups: tumors (hemangiomas, hemangioendotheliomas, and angiosarcomas) and malformations. VMs are classified based on the blood flow rate as slow flow (capillary, venous, and lymphatic) and fast flow (arterial and arteriovenous) [5]. VMs can also be divided into high-flow or low-flow lesions according to the ISSVA classification system. This classification was broadened and made more detailed during the 2014 ISSCA workshop in Melbourne, which further categorized VTs and VMs into subdivisions of these two groups. Tumors are classified according to their clinical behavior, whereas malformations are divided according to their flow characteristics, histopathologic features, and associations with other anomalies [6]. The classification system was recently updated during the May 2018 ISSCA meeting in Amsterdam [7]. Low-flow malformations involve a combination of venous, capillary, and lymphatic elements. Both these subsets grow with the patient without evidence of regression. Malformations are differentiated from tumors by the lack of mitoses and GLUT-1 negativity [8]. These lesions can affect the face, trunk, extremities, internal organs, bones, and skeletal muscle [9]. US and magnetic resonance imaging (MRI), along with MRA, are the most commonly used imaging modalities for vascular anomalies [9]. Indications for treatment are pain, appearance, and functional problems. Therapeutic approaches are sclerotherapy and, in selected cases, surgical resection [10]. VMs are defined by their particular blood vessel type of origin [11, 12]. Only a few case reports pertain to abdominal wall VMs. In a case report by Alessandrino et al., a 34-year old male had presented a soft, bluish, compressible lesion of the abdominal wall. US demonstrated dilated channels involving subcutaneous tissues, and color Doppler analysis revealed low flow within the vessels. MRI showed infiltrating non-mass-like lesions involving both superficial and deep tissues. This venous vascular malformation (VVM) extended from the skin through the subcutaneous tissues, infiltrating the rectus abdominis muscle [13]. In another case report by Kumar et al., a 21-year old female presented a soft, compressible mass in the left flank with palpable thrill and audible bruit. She complained of a dull aching pain for the past four years. US showed dilated vascular channels in layers of the posterior abdominal wall. A CT angiogram revealed a heterogeneously enhancing soft tissue lesion with multiple dilated tortuous vascular channels involving layers of posterior abdominal wall, compressing and displacing the left kidney anteriorly and superiorly. The AVM was fed by all four left lumbar arteries draining into the left common iliac vein. She underwent transarterial coil embolization followed by a surgical resection of the AVM. The patient is doing follow-up without any recurrence [14]. In another case report by Aravinda, the patient had a firm, noncompressible mass with normal overlying skin. US suggested a large hyperechoic mass in the left paramedian location extending from the epigastrium to the supraumbilical region, involving subcutaneous fat and anterior abdominal wall muscles. Contrast-enhanced computed tomography (CECT) revealed a well-defined abdominal wall mass involving the left rectus abdominis muscle, with prominent intralesional vascularity and enhancing perilesional neovascularity. The mass was fed by the left superior epigastric artery at the upper pole and the left inferior epigastric artery at the lower pole. Although the clinical features were not typical of an AVM, imaging findings, US, and CECT suggested otherwise, which was confirmed by a histopathological examination [15]. He underwent a surgical resection of the AVM. In our case, we presented an AVM not operated with an intramuscular location inside the left abdominal rectus muscle. We report the diagnostic pathway and the treatment plan for this pathological condition. AVMs are congenital high-flow VMs composed of dysplastic vessels, which form the nidus, and connect hypertrophied feeding arteries and large draining veins without an intervening capillary bed defined by their particular blood vessel type of origin [11, 12]. Histologically, an AVM is composed of dysplastic arteries intermingled among arterialized veins with thickened intimal lining. The endothelium, cultured from AVMs, has shown increased growth and reduced apoptosis, suggesting an intrinsic cellular defect [16]. Upon US examination, AVMs are shown to possess a mixed echogenic nidus with tortuous, hypertrophied arteries leading into the nidus. US can assess the vascularity of the anomaly, the types of vessels feeding the lesion, and the presence of a high-flow component [17]. The arterial feeders have a continuous diastolic flow, and the enlarged draining veins are arterialized, hence demonstrating a pulsatile flow [18]. Color-power Doppler US showing peculiar characteristics could suggest a benign or malignant disease [18] and sometimes even suspect the histological diagnosis of the lesion [19]. Furthermore, US allows us to quickly rule out other pathological conditions of the abdominal wall, such as hernias, abdominal wall endometriosis (AWE), desmoid tumors, lymphomas, metastatic carcinomas, sarcomas, and hematomas [17, 20, 21]. MRA and CECT are excellent methods for depicting the anatomical extent, multicompartmental involvement, and vascular angioarchitecture of the lesion [17]. The Schobinger staging system is currently used to classify AVMs based on their clinical presentation. Clinical signs of AVMs include dermatologic changes as well as cardiac irregularities in the most severe cases [22, 23]. There are four stages within the Schobinger staging system. Stage I AVMs initially present with dermatologic symptoms, such as skin that possesses a cutaneous blush or warmth resembling a port-wine stain [23, 24]. Stage II AVMs present with more noticeable features, such as bruits or thrills caused by circulation within the nidus as well as the presence of pulsatile masses. Stage III and IV AVMs involve pain and possible ischemic necrosis or ulceration of the tissue. Stage IV AVMs also involve high-output cardiac failure because of irregularity in systemic circulation putting a strain on the right side of the heart [25]. AVMs can become progressively symptomatic up to adulthood [26]. Infection, trauma, and hormonal changes in puberty and pregnancy are known factors that can trigger the rapid expansion of AVMs [22]. As they progress, they can cause more severe manifestations, such as swelling, ulceration, hard-to-control bleeding, deformity, and even congestive heart failure given the strain on right-sided cardiac output [27]. Schobinger staging also adopted a clinical classification system to provide helpful indicators to determine the timing of intervention [9, 23]. Young children were closely observed until disease expansion, with the concept that the treatment should not be worse than the disease [27]. However, this approach is currently being challenged because of the high recurrence rates experienced with AVM [28]. This is due to the collateralization and recruitment of new vessels to support an undetected portion of the “nidus” [29]. AVM treatment consists of embolization, surgical extirpation, or a combination of these modalities [25]. Treatment and timing are often individualized to the patient and the extent of the disease. Small-vessel AVMs are known to be localized and can be resected with good long-term outcomes [30]. Treatment is very much based on the impact of the lesions on the patient’s quality of life, weighed against the risk of complications. In most cases, conservative treatment is recommended, but if a patient develops peculiar complications, a surgical approach can be considered [31], balancing absolute and relative indications for specific interventions [32]. A variety of percutaneous sclerotic and transarterial embolizing agents have been advocated in numerous combinations, depending on the location, severity, and extent of the malformations. Absolute ethanol, bleomycin, 3% sodium tetradecyl sulfate (STS), polidocanol, ethanolamine oleate, n-butyl cyanoacrylate, polyvinyl alcohol foam, and various types of coils and polymer microspheres have all been used. The aim of the treatment of high-flow lesions is the complete occlusion of the AVM nidus or fistulous connection [9].

Abdominal wall VMs are uncommon diseases of the abdominal wall. In all the cases reported, sonography was used as the first diagnostic approach to evaluate the abdominal mass as it is safe and portable and does not involve ionizing radiation exposure. Moreover, the typical flow signal from color Doppler US can provide crucial information for the diagnosis. However, despite the US panoramic view, in all cases, studying the VMs using panoramic contrast imaging techniques (MRA and CECT) was necessary. On the other hand, determining the exact size/dimension of the malformation by means of US is challenging because its frequency range is limited, and in this sense, MRA is preferable to depict the anatomical extent and multi-compartmental involvement (i.e., compressive or infiltrative pattern) of the malformation. Given the clinical and surgical complexity of the malformations, a multidisciplinary approach involving a multi-specialist team is needed in managing these types of lesions. No unified agreement exists on the ideal treatment of these complex VMs, and a case-by-case basis multidisciplinary approach has been advocated. Sonography, color-power Doppler analysis, and panoramic imaging are excellent clinical tools for the follow-up of VMs. Funding No funding was received. Compliance with ethical standards Conflict of interest The authors declare that they have no conflict of interest. Ethical approval All procedures performed in studies involving human participants were in accordance with the ethical standards of the institutional and/or national research committee and with the 1964 Helsinki declaration and its later amendments or comparable ethical standards. This article does not contain any studies with human participants or animals performed by any of the authors. Informed consent Informed consent was obtained from all individual participants included in the study. A written permission was obtained from the patient. Footnotes Publisher's Note Springer Nature remains neutral with regard to jurisdictional claims in published maps and institutional affiliations.

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