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When Arteriovenous Malformation Arises In The Foot
These authors offer insights on the diagnosis and surgical excision of a rare presentation of arteriovenous malformation in the foot of a 51-year-old patient.
Arteriovenous malformations (AVMs) are defects of the circulatory system that arise during embryonic or fetal development or soon after birth. They are comprised of entangled arteries and veins without capillaries that pass blood directly from arteries to veins.1 The presence of an AVM disrupts this process, compromising the arteries from carrying oxygen-rich blood away from the heart to the body’s cells and compromising the ability of veins to return oxygen-depleted blood to the lungs and heart.1
Arteriovenous malformation is a rare condition and spontaneous regression is also rare. Arteriovenous malformations may be present throughout a person’s life with the origin time spanning from congenital abnormalities to manifestations thereafter from various stimuli such as trauma.2-7 The most common manifestations occur in the brain, lungs and lower extremity.4 One of the distinctive signs indicating the presence of an AVM is an auditory bruit, which one can assess during physical examination. Authors have described it as a rhythmic, whooshing sound caused by excessively rapid blood flow through the arteries and veins of a patient with AVM.1
One can differentiate high and low malformations by their hemodynamic and vascular architecture.8,9 Literature reports of AVM in the extremities have occurred with dermatologic manifestations but even more sparse are literature reports involving manifestations in the foot and ankle.10-12
A Closer Look At The Patient Presentation
A 51-year-old African-American male presented with a chief complaint of a painful soft tissue mass on his plantar medial left foot that had been present for two months and had increased in size. Pain was worse upon weightbearing. The patient reported having a similar mass on his shoulder that he had removed 21 years prior but was unsure of the diagnosis of that mass. He had no previous treatment other than walking on the outside of his feet to avoid direct contact with the mass but was having difficulty wearing certain shoes. He denies any trauma to the area. His past medical history included diabetes mellitus and sarcoidosis. He had a social history of smoking. A review of systems was unremarkable.
The patient’s physical exam revealed a large plantar medial soft tissue mass measuring 10 cm x 6 cm, slightly mobile, spongy in nature with visible lobular varicosities throughout the mass. The mass was non-pulsatile on palpation and did not transilluminate. The patient’s remaining pedal neurovascular and musculoskeletal examinations were within normal limits.
Radiographs revealed soft tissue changes on the medial aspect of the foot without any bony abnormalities. An ultrasound showed a mass of similar echogenicity of muscle with little vascularity, which ruled out soft tissue neoplasm. Magnetic resonance imaging (MRI) showed a lobular 10.0 x 5.6 x 3.2 cm T2 hyperintense mass that enveloped the flexor tendons.
No suspicious bone marrow signal was visible, which ruled out vascular malformation versus soft tissue tumor. The T1 weighted sequences showed diffuse enhancement within the large lobular mass and separate lobular foci medially and superficially, which represented superficial varicosities, which ruled out soft tissue malignancy. Differential diagnoses included vascular tumors such as hemangioma, Gorham-Stout disease or sarcomas such as liposarcoma, synovial sarcoma and malignant familial hyperplasia.
Key Pointers On Biopsy And Surgical Excision Of The Mass
In order to obtain biopsy results, we excised the mass with the patient under intravenous sedation. We used a local ankle block and a pneumatic ankle tourniquet. To rule out malignancy, we removed the mass in toto as opposed to performing an intralesional biopsy in order to avoid compromising the pseudocapsule and surrounding soft tissues with potential malignant tissue.
We performed a plantar medial longitudinal incision directly over the mass. The skin was thin at the most prominent aspect of the mass, which was well demarcated and delineated from normal surrounding soft tissue. The mass completely encapsulated and hypertrophied the abductor hallucis and flexor hallucis muscle bellies.
Keeping the flexor longus tendon intact, we bluntly dissected the subcutaneous tissue and muscle belly mass dorsally, medially and plantarly without causing compromise to the medial saphenous nerve or medial dorsal cutaneous nerve. Along the lateral aspect, we sharply separated the abductor and flexor hallucis muscle bellies from the surrounding intrinsic muscles and deep fascia. There were multiple varicosities within the mass and we had to cauterize the first metatarsal plantar vein. The deep peroneal nerve and medial plantar nerve and artery were intact. We passed the lesion from the operative field with markers made of sutures to help the pathology lab identify the location for possible further intervention if needed.
The surgical site had a large soft tissue void where we removed the mass. No pulsatile vessels were present. After deflating the tourniquet, we placed a Jackson-Pratt drain (JP drain) along the surgical site to prevent a hematoma. After using deep absorbable suture for subcutaneous closure and non-absorbable sutures for skin closure, we applied a Jones compressive dressing. The patient was admitted to the hospital for wound care and JP drain observation.
A frozen section of tissue revealed skeletal muscle with vascular proliferation, fibrocollagenous tissue and inflammation. Final pathology results revealed AVM with no evidence of malignancy.
We removed the JP drain on post-op day two and the remaining postoperative period was unremarkable. There were no complications of healing and the soft tissue remodeled with the patient’s own scar tissue during the healing process to fill in the void. He was immobilized for eight weeks until enough soft tissue formed under the plantar medial aspect of the foot to make it comfortable enough to bear weight. The patient had physical therapy to aid in ambulation due to the length of immobilization. He also wore accommodative custom-molded orthotics to provide padding and neutral position alignment when ambulating. After two years, there has been no recurrence and he has resumed all normal activities to tolerance.
Further Insights On Treating Patients With AVM
Arteriovenous malformations rarely occur in the lower extremities. We can best characterize them by the type of vascular channel, the degree of blood flow and the structures involved. The most common sites of these lesions are the pelvis, extremities and intracranial circulation.13 They occur with an incidence of 1 to 10 in 1 million and are apparent in 1 to 2.6 percent of neonates.14 Arteriovenous malformations are frequently associated with additional findings and fall under the auspices of multiple syndromes (see “Syndromes With Associated Arteriovenous Malformations” at the left).15
As we discussed earlier, one can differentiate high and low flow malformations by their hemodynamic and vascular architecture.8-9 Low flow lesions comprise capillary, lymphatic and venous malformations.
High flow AVMs are characterized by a high blood flow in a direct connection between arteries and veins without capillaries.16 The Schobinger staging system of arteriovenous malformations includes four grades of severity: dormancy, expansion, destruction and decompensation.7
Clinically, if a palpable mass is present, it is generally firm and non-compressible.2 As we mentioned, one of the distinctive signs indicating the presence of an AVM is an auditory bruit. Authors have described it as a rhythmic, whooshing sound caused by excessively rapid blood flow through the arteries and veins of a patient with AVM.1 Other clinical findings include increased warmth to the affected limb and a dermal stain at the site of the mass. Waterson and colleagues stated that a bruit or thrill arises in relatively few extremity cases because the flow is usually through multiple small communications.10
In this presented case, a high flow AVM involved the first metatarsal plantar vein, which we cauterized. This malformation would most likely be Stage II, the expansion phase on the Schobinger staging system. We could not determine the cause of expansion and clinical manifestation of this AVM. Clinically, the mass was non-pulsatile, slightly mobile and spongy in nature. A bruit was not present in this patient. Due to the patient noticing this mass increase in size over two months, we needed to rule out soft tissue malignancy and surgical excision was the best treatment option.
In conclusion, to diagnose these types of lesions appropriately and to avoid unnecessary treatment, we recommend interdisciplinary therapy and surgical excision if necessary.
Dr. Judd is a Diplomate of the American Board of Foot and Ankle Surgery. She is a Podiatry Attending with Surgical Services at the Department of Veteran Affairs Medical Center in Washington, DC.
References
1. National Institute of Neurological Disorders and Stroke. Arteriovenous Malformation Fact Sheet. Available at https://www.ninds.nih.gov/disorders/avms/detail_avms.htm. Published February 23, 2015.
2. Rosen RJ, Riles TS, Berenstein A. Congenital vascular malformations. In Moore WS (ed.) Vascular Surgery, Fourth Edition, Saunders, Philadelphia, 1985, pp. 1049-1061.
3. Kellerhouse LE, Ranninger K. Congenital arteriorvenous malformation of the foot. Am J Roentgenol Radium Therm Nucl Med. 1969; 105(4):877-879.
4. Shetty PC, Benenson J, Collison DW, Burke TH. Successful embolization of multiple AV foot lesions: a case history. Angiology. 1990; 41(6):492-497.
5. Ducksoo, K, Orron DE. Peripheral Vascular Imaging and Intervention. Thieme Stugart, New York, 1994, pp. 165-167.
6. Rosen RJ, Riles TS, Berenstein A. Vascular Surgery, Third Edition. Saunders, Philadelphia, 1989, pp. 1049-1061.
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10. Waterson KW, Shapiro L, Dannengerg M. Developmental arteriovenous malformation with secondary angiodermatitis-report of a case. Arch Dermatol. 1969; 100(3):297-302.
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14. Holmdahl K. Cutaneous hemangiomas in premature and mature infants. Acta Paediatrica Scandinavica. 1955; 44(4):370-9.
15. Kasirajan K, Ouriel K. Vascular malformation and arteriovenous fistula. In: Greenfield LJ (ed.) Surgery: Scientific Principles and Practice, Volume 3, Third Edition. Lippincott Williams & Wilkins, Philadelphia, 2001, pp. 1859-1871.
16. Kunze B, Kluba T, Ernemann U, Miller S. Arteriovenous malformation: an unusual reason for foot pain in children. Foot Ankle Online J. 2009; 2(12):1.
17. Schobinger RA. Diagnostische und therapeutische Moglichkeiten bei peripheren Angiodysplasien. Helv Chir Acta. 1971; 38(3):213-220.
