May-Thurner syndrome (MTS) does not commonly cause leg edema, pain, or deep vein thrombosis (DVT). However, general understanding of the cause of MTS is left common iliac vein compression by the right common iliac artery and lumbar vertebral body (1). An iliac arteriovenous fistula (AVF) is also a rare condition caused by congenital and iatrogenic trauma (2). MTS is mostly treated using endo-vascular therapy (i.e., stenting and thrombectomy). However, a management strategy for coexisting iliac AVF(s) has not yet been established. We present a case of MTS coexisting with an AVF that was successfully treated using an endovascular procedure.

An 82-year-old female was referred from a local clinic due to persistent left leg edema caused by subacute onset of DVT. She experienced leg edema for 1 year and recent aggravation for 1 month. The patient had diabetes mellitus, hypertension, and dementia, with no history of spinal or gynecological surgery. The patient’s vital signs were unremarkable, although she exhibited a leg circumference discrepancy of 4 cm, with pretibial pitting edema.

The patient underwent ultrasound examination at a local clinic, which revealed DVT in the left iliac vein. She was administered a direct oral anticoagulant (rivaroxaban, 20 mg sod) and prescribed medical compression stockings for 1 month. Computed tomography (CT) angiography revealed DVT in the left popliteal vein, with a totally collapsed iliac vein and leg swelling. Early filling sign of the left femoral vein was also noted.

Femoral venography revealed total occlusion of the left iliofemoral venous system (Fig. 1A). The patient was treated using percutaneous transluminal angioplasty (PTA) alone (Fig. 1B-D). After the first procedure, the patient’s leg circumference discrepancy was not immediately corrected. Follow-up CT angiography revealed significant extrinsic compression of the left common iliac vein, which is a characteristic finding of MTS. An additional procedure involved stent placement in the common iliac vein using a 10×80 mm self-expandable stent (Boston Scientific, Marlborough, MA, USA) (Fig. 2). This additional procedure resulted in full resolution of left leg edema without a circumference discrepancy. The patient was administered a direct oral anticoagulant and prescribed medical compres-sion stockings after the procedure. Three months after the procedure, however, the patient visited the clinic again due to recurrent left leg edema. The authors decided on a combined procedure address to MTS and AVF. The MTS management maneuver included PTA and placement of an additional stent for in-stent occlusion and AVF closure using coil embolization (Fig. 3). Arteriography of the left lower extremity was performed via right common femoral artery puncture. Selective catheterization of the left internal iliac artery revealed an arteriovenous connection from one branch that was successfully coiled using a 3∼4 mm coil (Boston Scientific). Completion angiography demonstrated significantly improved residual—but minimally delayed—filling. Subsequently, the patient’s leg edema resolved. Comparison of leg circumference was remarkable (at admission, right thigh 37.2 cm; left thigh, 38.2 cm; right calf, 27.6 cm; left calf, 33.4 cm; at discharge, 42, 41, 26.5, and 26.5 cm, respectively).

Figure 1. (A) Computed tomography revealing an iliac arteriovenous fistula with no visualization of the iliac vein system. This figure was rotated 270 degrees to improve visualization of the left ilio-iliac fistula with interruption of the iliac vein. (B) Femoral venogram revealing no visualization of iliac vein system, with suspected generalized hypoplasia. (C) Passage of a 0.014-inch guide wire revealed the iliac vein system and enography revealed a large collateral within the pelvic cavity. (D) Percutaneous transluminal angioplasty (3×40 mm and 6×40 mm) revealed restoration of normal iliac vein flow.

Figure 2. (A) Bilateral venogram revealing characteristic findings of May-Thurner syndrome in the left common iliac vein (CIV) due to compression between the right common iliac artery and vertebral body. (B) After placement of a 10×60 mm stent in the CIV, angiography demonstrates proper flow via the left iliac system.

Figure 3. (A) Reconstructed computed tomography (CT) angiogram revealing significant iliac arteriovenous fistula (AVF). This view was rotated 270 degrees to improve fistula flow. (B) Before coil embolization of the AVF, findings reveal large amount of shunt flow into the iliac venous system. (C) Coil embolization reducing fistulous flow. (D) Follow-up CT angiography revealing disappearance of the AVF in the iliac artery and vein.

MTS is a condition in which the left common iliac vein is compressed by the right common iliac artery and the lumbar vertebra. This may have caused swelling or DVT in the left lower extremity. MTS was first described by May and Thurner in 1957 (1). This syndrome causes swelling and DVT. Treatment of MTS usually involves clearing the thrombus and correcting the compression of the left iliac vein. Endovascular therapy with thrombolysis and stenting is considered the first-line treatment for MTS because patients with extrinsic causes of obstruction tend to respond poorly to balloon angioplasty alone. (3) Pogorzeski et al. (4) reported that endovascular therapy is be good method for MTS, and stenting for MTS resulted in good long-term (two-year) patency.

The etiology of ilio-iliac AVF(s) is variable and includes congenital, iatrogenic, and trauma. However, MTS coexisting with left iliac AVFs is a rare phenomenon. In this case, there was no aneurysm, catheter insertion, or history of trauma. It is very difficult to establish etiological relationships. In rare cases of AVF formation within a thrombosed vein, it has been hypothesized that hypoxia, shear stress, and venous hypertension result in the upregulation of hypoxia-induced microvascular growth (5). The patient described in this report exhibited no evidence of a previous DVT; however, she may have had an unrecognized history of DVT combined with MTS.

Conventionally, some authors recommend small-size, temporary femoral AVF formation that is helpful in maintaining the open state of the stent on the iliac vein. Therefore, many vascular surgeons neglect the presence of small-size AVFs. AVFs may have inhibited antegrade venous blood flow due to the Venturi effect and worsened edema in the lower extremities (6). A generally recognized cause of leg swelling is aggravation of flow caused by AVF(s) through the interrupted iliac vein system. In cases of severe leg edema, after development of iliac AVF, treatment with embolic occlusion of the fistula is a very effective maneuver for improving leg swelling. Hyunh et al. and Raju et al. reported that iliac vein stenting is safe and effective in elderly patients 80∼96 years of age (7).

Haijie et al. reported that embolization resulted in decreased venous pressure, and opening and stenting of the occlusion of the iliac vein further reduced venous flow resistance (8). In addition, the development of collateral circulation may lead to pelvic congestion syndrome and require attention. If the iliac vein was treated alone and the AVFs were not treated, pulmonary hypertension could have developed.

The patient described in the present report was treated using a general strategy for MTS; more specifically, PTA with stenting first, and addressing coexisting left iliac AVFs. Recurrence of DVT with leg edema forced AVF closure using an endovascular procedure.

Coexisting AVF with MTS may be an overlooked lesion. Clinicians should consider the presence of coexisting vascular anomalies when managing patients with MTS. Endovascular therapy using embolization and stenting can provide adequate resolution of these lesions. To date, the pathogenic mechanism of spontaneous-onset AVFs coexisting with MTS remains unclear. This report may raise awareness of these vascular lesions among vascular surgeons in the field.