May-Thurner Syndrome in a 68-Year-Old Woman after Remote Abdominal Surgery

Abstract

May-Thurner syndrome, also called iliac vein compression syndrome, is a rare cause of left iliac deep vein thrombosis, which arises from pulsatile compression of the left common iliac vein by the right common iliac artery. The resultant endothelial damage and intraluminal spur formation can lead to iliac deep vein thrombosis and sudden-onset left-lower-extremity edema and pain. Patients typically present with May-Thurner syndrome in their 2nd to 4th decades of life. In chronic form, the syndrome can be debilitating because of venous claudication and stasis ulcers. Surgical approaches and endovascular interventions have been effective in the acute phase of the disease, and intravenous stents can resolve the manifestations of chronic venous compression. Anticoagulation alone is ineffective, and a consensus regarding the usage and duration of antiplatelet and antithrombotic therapy has not been established.

We present the case of a 68-year-old woman with a remote history of abdominal surgery who presented with left-lower-extremity edema and pain. Magnetic resonance venography of the pelvic veins yielded a definitive diagnosis of May-Thurner syndrome. Catheter-directed thrombolysis and intravenous stent placement resolved her symptoms, and she was discharged from the hospital on anticoagulative therapy. A year later, she had no residual pain or edema, and the affected veins were patent with normal phasic flow and normal responses to compression and augmentation.

Acute lower-extremity deep vein thrombosis (DVT) or chronic venous stasis can be a manifestation of May-Thurner syndrome (MTS). In MTS, the right common iliac artery compresses the left common iliac vein against the 5th lumbar vertebra, resulting in intraluminal changes that predispose patients to left-lower-extremity DVT.^1,2 Although MTS is an underrecognized cause of left iliofemoral venous thrombi, it is the ultimate diagnosis in 2% to 5% of patients who are evaluated for lower-extremity venous disorders.³ Treatment for pelvic venous thrombosis secondary to MTS includes catheter-directed thrombolysis (CDT), balloon angioplasty, and stent placement at the compression site.^4,5 However, there is no consensus about the optimal usage and duration of antiplatelet, antithrombotic, and anticoagulative therapy after stent placement.

Patients with MTS usually present in their 2nd to 4th decades of life.⁶ Pregnancy and intra-abdominal surgeries are known precipitating factors in acute MTS.⁶ We report the case of a woman who presented with MTS in her 7th decade of life, several years after she had undergone intra-abdominal surgery.

Case Report

In September 2010, a 68-year-old woman presented with a 3-day history of left-lower-extremity edema and pain. Physical examination findings were significant for varicose veins and a positive Homans sign in her left lower extremity. The patient's left thigh was 48 cm in circumference (vs 40 cm on the right), and her left calf was 40 cm in circumference (vs 34 cm on the right) (Fig. 1A). Compression stockings and empiric therapy with subcutaneous enoxaparin yielded minimal resolution of her symptoms. Lower-extremity Doppler ultrasonography showed no evidence of DVT. On contrast computed tomographic (CT) examination of the patient's abdomen and pelvis, no thrombus was identified; however, an enlarged confluence of the left external and internal iliac veins with minimal stranding around the internal vein suggested DVT. Magnetic resonance venography showed an occlusive thrombus in the left common iliac vein, extending from the vein's origin to its bifurcation; an occlusive thrombus extending into the proximal left internal iliac vein; and a partially occlusive thrombus extending into the proximal left external iliac vein. The left common iliac vein was markedly narrowed where it was interposed between the right common iliac artery anteriorly and the vertebral body posteriorly (Fig. 2), and the diagnosis of MTS was established.

Fig. 1 Photographs show the patient's appearance A) upon presenting with a 3-day history of left-lower-extremity edema, and B) upon clinical resolution of the edema after catheter-directed thrombolysis, balloon angioplasty, and stent placement.

Fig. 2 Magnetic resonance venogram shows compression of the left iliac vein (white arrow) and distal associated pelvic venous thrombosis (black arrow).

A subsequent examination was negative for thrombophilia. The patient's medical history included no DVT, malignancy, recent surgery, or prolonged immobilization; however, she had undergone both a total abdominal hysterectomy and the surgical repair of a cystocele more than 5 years previously. Two years before the current presentation, she had been given aspirin and dipyridamole after a transient ischemic attack.

We treated the patient's MTS with CDT and subsequent balloon angioplasty with stent placement. Access to the left common femoral vein was achieved with use of a 21G micropuncture needle at an appropriate level, determined fluoroscopically under real-time ultrasonographic guidance. Venous access was increased to a 0.035-in system in usual fashion, and a Bentson wire was passed through the sheath into the left external iliac vein. A venogram through the sheath showed a long-segment stenosis of the left common iliac vein. Several filling defects in the femoral and iliac veins were consistent with thrombus. A Bentson wire and 5F Kumpe catheter were used to cross the stenosis and occlusions. A 10-cm infusion catheter was placed with its distal tip in the distal inferior vena cava (IVC) and its proximal tip in the left common iliac vein. Ten mg of alteplase in 1,000 cc of normal saline solution was infused through the catheter at a rate of 0.5 mg/hr, and 300 U/hr of heparin was infused through the sheath for 24 hours. The patient's fibrinogen level, partial thromboplastin time, prothrombin time, and hemoglobin level were monitored every 6 hours. After thrombolysis, a venogram through the infusion catheter showed interval resolution of the acute thrombus within the external iliac vein and pelvic vessels. A venogram through the sheath showed a long-segment stenosis of the left common iliac vein, with multiple collateral vessels. Subsequent serial angioplasties of the vein were performed with use of 8-, 10-, and 12-mm balloons. A venogram then showed improved flow. A 12 × 60-mm uncovered nitinol stent was deployed (Fig. 3). A subsequent venogram showed adequate positioning of the stent and improved flow through the left common iliac vein, and the collateral vessels were not seen (Fig. 4).

Fig. 3 Venogram shows balloon angioplasty (white arrow) and stent placement (black arrow) in the left common iliac vein.

Fig. 4 Magnetic resonance venogram shows restored venous flow in the left common iliac vein after catheter-directed thrombolysis, balloon angioplasty, and stent placement.

The patient's symptoms rapidly resolved (Fig. 1B). She was given aspirin, dipyridamole, and an intravenous heparin infusion, and she was bridged to oral anticoagulation with warfarin. Upon 12-month follow-up, she had no lower-extremity edema. An ultrasonographic examination revealed that the left common femoral vein, superficial femoral vein (including the femoral bifurcation), and popliteal vein were patent. All the veins had normal phasic flow and responded normally to compression and augmentation.

Discussion

May-Thurner syndrome is both a mechanical and a physiologic problem.⁶ Chronic pulsatile venous compression by the right common iliac artery is responsible for the formation of intraluminal webs or spurs at the compression site.^1,6,7 The resultant endothelial injury and turbulence in blood flow leads to thrombus formation. This progression—from asymptomatic venous compression to spur-formation and then to thrombosis—constitutes the stages of iliac vein compression syndrome.^8–10 Although classic MTS is described as compression of the left iliac vein and right common iliac artery, compression of the right iliac vein and IVC has also been reported.^11–13

Patients can present during the acute or chronic phase of MTS. Surgical intervention for gynecologic¹⁰ and abdominal pathologic conditions¹⁴ has been described as a precipitating factor. Acute manifestations include sudden-onset left-lower-extremity edema and pain, often triggered by surgery, pregnancy, or febrile illness, including pneumonia and pleurisy.^6,15–17 Acute MTS can be life-threatening if there is associated pulmonary embolism or a spontaneous retroperitoneal hematoma associated with iliac vein rupture.¹⁸ Chronic MTS is the result of long-term venous hypertension and is characterized by lower-extremity edema, venous claudication, and stasis ulcers. Untreated patients tend to have recurrent and perhaps lifelong episodes of thrombosis and phlegmasia cerulea dolens.^3,6,19

The diagnosis of MTS is made only after excluding other sources of venous occlusion, such as malignancy, trauma, surgery, and radiation.^7,15 The standard test for DVT, color duplex ultrasonographic imaging, is not sensitive enough to detect acute iliofemoral DVT and is therefore inadequate.¹⁵ A CT scan can be used to rule out malignancy or masses as possible causes of compression; however, standard CT with 10-mm slices can miss intravenous spurs or fibrosis.²⁰ Magnetic resonance venography is the technique of choice, because it identifies the area of compression and also reveals collateral vessels, as in our patient.^21–23

In MTS patients, treatment is directed toward alleviating discomfort and preventing life-threatening complications. The chief treatment has been anticoagulative therapy. Although anticoagulation prevents clot propagation, the existing clot and the mechanical compression persist. Anticoagulation alone and thrombectomy with prospective anticoagulation yielded a repeat-thrombosis rate of up to 73% in patients who had a venous spur.^24,25 Endovascular management should be the first-line treatment for acute iliofemoral DVT.^15,17,26 Catheter-directed thrombolysis is the most appropriate initial therapy for acute iliac vein thrombosis.^15–17 In this fluoroscopically guided procedure, an infusion catheter is used to deliver a high dose of thrombolytic agent directly into the venous thrombus. This advantage maximizes the therapeutic effect, ensures long-term patency, and minimizes the risk of bleeding.^5,27 Continuous intravenous heparin infusion adds a synergistic effect to CDT. During CDT, several laboratory values are monitored: fibrinogen, to detect clot lysis; activated partial thromboplastin time, during heparin infusion; prothrombin time, to determine disseminated intravascular coagulation; and hemoglobin, to detect bleeding (especially occult gastrointestinal bleeding).

An invasive catheter-based technique to aspirate, macerate, or otherwise disrupt venous thrombus—percutaneous mechanical thrombectomy—is complementary to CDT, and without it the risk of pulmonary embolism could increase. Although CDT diminishes the thrombus burden by means of chemical dissolution, and endovascular balloon angioplasty restores intraluminal patency, mechanical compression by the right common iliac artery persists. Relief is achieved by means of stent placement. Endovascular stenting obliterates spur formation and maintains long-term venous patency,^21–23 and the technique is superior to balloon dilation alone.²⁸ Large self-expanding stents placed across the stenosis and into the IVC are preferred, because they help to prevent stent migration. The self-expanding nitinol stent, made from an alloy of nickel and titanium, has good radial strength and flexibility. It can be especially useful in the presence of a long stenotic segment and tortuous course—unlike balloon-expandable stents, which are made of steel and can be used only for shorter segments. A study by Neglen and colleagues²⁹ determined low morbidity and mortality rates, high patency rates, and good relief of major symptoms after nitinol stenting of the venous outflow tract in chronic venous disease. In addition, the stented limbs with nonthrombotic iliac vein lesions—as in MTS—had a lower cumulative occlusion rate than did limbs with thrombotic disease (1% vs 10%).²⁹ Intravascular ultrasonography further enables diagnostic and therapeutic aspects of these endovascular interventions by providing information on vascular size and morphology.³⁰ This method can be superior to venography in determining the degree and extension of iliofemoral occlusive lesions and thereby obviating secondary stenting procedures for restenosis.^31,32

Surgical intervention for MTS that presents with acute thrombosis includes mechanical thrombectomy with intentional arteriovenous fistula (AVF) formation and mechanical dissection to relieve the obstruction caused by the compression of the left common iliac vein by the right common iliac artery.³³ Procedures to correct chronic venous obstruction include venous bypass (including saphenofemoral and ilioiliac crossover), arterial repositioning, fascia lata sling, peritoneal flap, patch angioplasty, and aortic reconfiguration.³⁴ Saphenous vein grafts have poor long-term patency rates, because the greater saphenous vein has a smaller lumen than does the iliac vein.⁶ Reinforced polytetrafluoroethylene grafts have reportedly yielded the best success in venous bypass procedures. However, open surgical reconstructions are challenging, and the success of the operation depends on the type of conduit, the graft material, adequately low venous pressure, and the presence of thrombophilia.

Because patients with nonthrombotic venous obstruction typically experience good results after endovascular venous stenting, this procedure is now proposed as the first interventional option. A study of factors affecting the outcome of open and hybrid reconstructions for nonmalignant obstruction of the iliofemoral veins and IVC showed significantly decreased primary and secondary patency rates in the presence of MTS.³⁵ Upon sensitivity and subgroup analysis, this was true for all procedure types, although the phenomenon was unexplained by the available evidence. Femorocaval bypass (complex bypass) and hybrid reconstruction are 2 procedures that have been performed in the case of iliocaval disease (Table I). Intraoperative AVF formation was performed during the initial procedure (40.6%) and during reoperation for graft failure (12.5%) to increase graft flow. Primary AVF formation was associated with decreased primary and secondary patency rates, although not at a level of statistical significance.³⁵ Endovascular stenting should therefore be the primary choice for treating MTS.^15,36

TABLE I. Surgical Interventions for May-Thurner Syndrome

Some investigators have advocated antiplatelet therapy with clopidogrel for 6 weeks²¹ and oral anticoagulation with warfarin for 3 to 6 months after venous stent placement. However, the exact usage and optimal duration of these therapies is not well defined. There is a positive correlation between the use of antiplatelet and oral anticoagulative medications and the risk of hemorrhagic events. Large-scale prospective studies are needed to identify optimal therapy in the postoperative management of venous stent placement.

Of note, our patient did not present with any symptoms until the age of 68 years, which is substantially older than the typical MTS patient. Accordingly, we suggest that abdominal and pelvic surgery not only predisposes an individual to an increased risk of developing acute MTS, but also affects their risk years later. Table II lists cases of MTS that were managed with endovascular intervention, and the clinical features and therapies.^19,37–41 Retrospective or prospective analyses are needed to ascertain the long-term risk that MTS will develop after surgery.

TABLE II. Clinical Characteristics and Management of Patients with May-Thurner Syndrome