A Systematic Review of Radiological Diagnosis and Management of May–Thurner Syndrome

ABSTRACT

May–Thurner syndrome (MTS) is an anatomical condition of external luminal compression of common iliac vein due to a partial obstruction of the common iliac vein between common iliac artery and lumbar vertebra causes deep-vein thrombosis, venous hypertension, and chronic venous insufficiencies. In this article, we review present evidence of the clinical diagnosis and management of MTS. Here, we conducted a literature review of studies on MTS. We also reviewed different clinical features, presentation, diagnostic methods, and therapeutic procedure for this condition. Most studies mentioned the diagnosis of this condition is performed by color Doppler, computed tomographic angiography, venography, and problem-solving cases by intravascular ultrasound technique. Nonsurgical methods of management are first line, and vascular surgery is reserved for refractory cases. Multiple modalities are required to reach the diagnosis of MTS, and noninvasive intervention radiology methods are the first line of management. This review highlights the presentations of MTS and outlines diagnostic procedure and management.

INTRODUCTION

Left iliac vein compression due to an unknown cause was first mentioned by Mach Murich in 1908.[1] In 1957, May and Thurner found intraluminal venous spur in about 22% of cases in an anatomical examination of 430 cadavers.[2] The direct relation between the iliac wind compression and thrombosis was first illustrated in 1967 by Steinberg et al.[3] The majority of cases are left-sided,[4] however, a few cases of right-sided May–Thurner syndrome have also been reported.[5,6]

Aim

This review article is to summarize the present state of knowledge regarding the diagnosis and management of MTS.

MATERIALS AND METHODS

Here, a comprehensive search for literature is performed using online databases such as PubMed and Google Scholar for the studies published in English between 2000 and 2023 for the cases of MTS, and the clinical presentation, diagnostic methods, and methods of management are studied.

Keywords used for the search included May–Thurner syndrome, varicose veins, chronic venous insufficiency, iliac stenting, complications of MTS, and surgery for MTS. Relevant studies are identified through proper screening by reading the full article texts.

RESULT

Etiology and pathogenesis of MTS

The left common vein is more horizontal in course and, hence, more prone to compression after its origin than the right common iliac vein, which is a possible cause of compression. The continuous physical pressures from the overlying artery. There is spur formation within the affected veins. Due to the chronic pressure of the overriding right iliac artery there is entrapment of the left iliac vein between the bony structures, usually the lower lumbar vertebrae. Rarely has MTS been reported on the right side.[7,8] Venous valve defect is also attributable to these conditions.[9] There is further activation of the Virchows triad leading to deep-vein thrombosis by stasis, hypercoagulability state, and underlying endothelial injury, which later forms venous spur and deep-vein thrombosis (Dvt).[10,11,12] The chronic DVT can lead to features of chronic venous insufficiency (CVI) edema, pain, varicose veins, venous ulcers, and pulmonary embolism in about 18-49% of cases.[13,14] In spite of the majority of these cases with anatomical compression being asymptomatic,[15]

Epidemiology

Among the symptomatic cases, MTS has been associated with about 2-5% of all DVT.[16,17] Among asymptomatic cases, its prevalence in retrospective cadaveric and radiological cases is much higher, seen up to 14-32%.[16] Risk factors include female gender, more common in females in a 2^nd-4^th decade, multipara status, associated intake of contraceptive pills, vertebral deformities such as scoliosis, posttraumatic deformities, dehydration, and hypercoagulable states.[4,16,18,19,20] Studies have mentioned twice incidence in female gender with more association with DVT and pulmonary embolism. Among affected males, pain in the leg and edema were common symptoms.[21]

Clinical features

Majority of cases of MTS are asymptomatic, few symptomatic cases present with unilateral, preferably left lower limb pain, edema, varicose veins, venous ulcers, and hyperpigmentation.

Features of CVI due to venous hypertension are varicose veins, ulcers, hyperpigmentation, activity-related discomfort, and swelling of the left lower limb or claudication pain, which is relieved by rest and foot elevation.[22,23] Cases rarely develop phlegmasia cerulea dolens.[24] Sometimes patients can present with shortness of breath, chest pain, and later symptoms of pulmonary thrombolism.[25] Postthrombotic syndrome and recurrence can be seen in the treated cases of MTS.

Diagnosis

Diagnosis is performed by the use of multiple modalities.[26] Pathological examination to rule out primary causes of hypercoagulation by evaluation serum.

Pathological examinations are performed to rule out causes of hypercoagulability by an appropriate check to the level of antithrombin, C reactive protein, Protein S, prothrombin, Factor V Leiden, antiphospholipid antibody, and prothrombin G20210A.

Ultrasound (US)/color Doppler: This is the most common useful modality used to diagnose an MTS; however, this exam is more operator-based and depends on the technical expertise of the operator.[27] Presence of DVT, varicosities, incompetent perforators, and incompetent valves for CVI is diagnosed. The presence of deep venous reflux [Figure 1] in deep veins is an important sign of obstruction above, and here, the search for the cause of resistance in the venous return at the iliac veins and inferior vena cava (IVC) is necessary to establish. The increased velocity of common iliac vein blood may indicate iliac venous compression. In the presence of thrombosis at the iliac artery and IVC junction, compression can be identified; however, it can be missed depending on the bowel preparation and body habitus of the patients. These technical difficulties in assessing the IVC and iliac vein can limit their use and mandate more objective methods to diagnose the condition.

Figure 1.

Showing deep venous reflux on valsalvamaneuver in the case of MTS in left common iliac vein

Contrast-enhanced computed tomography (CT) and CT venography (CTV) are more sensitive and specific methods to detect the iliac venous compression nearing 95%. This is also useful for ruling out other causes of compression of iliac veins, such as lymph node enlargement, any abdominal mass, and cellulites.[28] The presence of bony abnormalities can also be assessed by using bone windows and reformatted images. The left iliac vein with filling defect and flattening below the right iliac artery can be seen in MTS [Figures 2-4]. CTV cannot account the volume status of the patient and can show a flattened vein in a dehydrated patient is a common pitfall in this modality.[29]

Figure 2.

Axial computed tomography images in venous phase showing filling defect in the left common iliac vein and flattening

Figure 4.

Axial computed tomography venogram images showing left common iliac vein flattening and compression by the right common iliac artery

Figure 3.

Axial computed tomography images in venous phase showing compression of left common iliac vein, flattening by the right common iliac artery

Magnetic resonance venography (MRV) is an alternative modality that provides evidence of iliac venous compression to diagnose MTS by the time of flight and post-Gad imaging. This is not an adequate modality to diagnose MTS due to the variability of iliac vein compression over time and limited availability and cost.[30]

Venography with intravascular US (IVUS) is the gold standard technique to diagnose MTS. Venogram give real-time images with patency of the venous lumen. Venogram also give information of pre and postprocedure patency of vein and stent and also guide for balloon angioplasty. IVUS gives a real-time evaluation of the vascular lumen, gives the accurate size of lumen, and provides accurate information about the structural changes in the vein wall.[31]

The IVUS also gives additional information about the chronicity of the venous thrombus, which could help more in deciding the management for a decision to perform thrombolysis. IVUS can also localize guide wires during venogram procedures in challenging recanalizations with multiple collaterals of the veins and helps in accurately placing stents in the vein.[26] There is no use of contrast in this technique, which makes it more safe for nephropathy and hypersensitivity patients.

Differential diagnosis

Causes of iliac vein compression can be a differential diagnosis as pelvic malignancy, retroperitoneal lymphadenopathy, pregnancy, aneurysms of pelvic iliac arteries, bony outgrowth, or deformities, and retroperitoneal fibrosis.

Management

Asymptomatic cases require no treatment among the symptomatic cases presenting with acute episodes of DVT (<2 weeks of duration) or CVI features. Other risk factors and secondary causes of venous compression are ruled out. Once diagnosis is established, management planning is performed. The cases with acute DVT and MTS are started on anticoagulation. The use of prophylactic filter placement is controversial; some advise for large thrombus in IVC or for recurrent pulmonary thromboembolism (PTE), but the low incidence of PTE in MTS filter placement is rarely required.[21,32] Use of catheter-directed thrombolysis followed by placement of stentis advised.[33,34,35] Surgical thrombectomy is less recommended due to less invasive options.[36] Surgical procedures are reserved for failed and recurrent cases as different venous bypass surgeries.[17] Recent recommendation of rivaroxaban is also advised.[37] Recently, the Society of Interventional Radiology recommended endovascular removal of thrombus and stenting in cases with acute iliofemoral DVT.[38]

DISCUSSION

About one-third of the population can have hemodynamically significant compression of the left iliac vein in pelvis by the overlying right iliac artery. It is currently estimated that up to ⅓ of humans have hemodynamically significant compression of their left iliac vein by the overlying right iliac artery.[39] Multiple studies have shown that the clinical diagnosis of MTS is made using a multimodality approach.[26] Color Doppler is the best initial noninvasive technique showing deep venous reflux with features of CVI. These findings are confirmed by the CT venogram, MR venogram, and gold standard test by digital subtraction venogram. IVUS is the best problem-solving tool in equivocal cases.[31] Few studies favor use of catheter-directed thrombolysis followed by placement of an endovascular stent in cases of MTS, while few state this alone is not sufficient for MTS.[33,34] As per the guidelines of the Society of Interventional Radiology and also by the Society of Vascular Surgery iliac venous stenting in MTS is recommended.[35]

The cases with acute DVT and MTS are started on anticoagulation, which is initially by unfractionated heparin intravenous infusion titrated according to activated partial thromboplastin time (aPTT). Use of prophylactic filter placement in IVC is not recommended.[21] Placement of IVC filters for cases with large or floating thrombus in IVC, history of recurrent pulmonary thromboembolism (PTE), or any contraindication for anticoagulation can be performed. Due to the very low incidence of PTE in MTS because of the protective effect of venous stenosis, the method of filter placement is rarely required.[32]

Few studies favor use of catheter-directed thrombolysis followed by placement of the endovascular stent in cases of MTS, while few state this alone is not sufficient for MTS.[33,34] As per the guidelines of the Society of Interventional Radiology and also by the Society of Vascular Surgery, iliac venous stenting in MTS is recommended.[35] The contraindications of catheter-guided thrombolysis are evidence of brain infarcts, ophthalmic, and neurological procedures, head injury for 3 months, any vascular malformation, pregnancy, renal or liver disease, and bleeding diathesis.

Surgical thrombectomy is less recommended in present availability of minimal invasive techniques over surgical dissection due to morbidity from anesthesia and surgery.[36]

Surgical procedures are reserved for failed and recurrent cases. These surgeries are sapheno-femoral bypass, pelvic vein cross bypass, prosthetic femoro-femoral bypass, venacaval-femoral bypass, prosthetic ilio-iliac bypass, and aortic elevation procedures.[17]

Overall, all the above-mentioned studies suggest that timely identification of clinical features, proper ruling out of other causes and differential diagnosis and establishing a timely diagnosis of MTS are key factors for adequate management and secondary prevention. A follow-up of asymptomatic cases and education regarding the situation can be advised. Due to the availability of different nonsurgical daycare procedures, the morbidity and disability caused by MTs are adequately controlled. In developing countries, due to the rare availability of facilities like interventional laboratories and digital subtraction angiography the proper diagnosis and management is still challenging. Endovascular stenting is the 1^st-line therapy over endovascular balloon angioplasty due to the additional relief from the external compression in MTS.[40] Nonthrombotic iliac venous compression is an important cause for recurrence and failure of varicose vein surgery, and hence, proper diagnosis of MTS is timely and mandates proper management.[41]

CONCLUSION

Diagnosis of MTS requires a high index of clinical suspicion. Color Doppler study with features of DVT, CVI, along with deep venous reflux, gives enough clinical hints to proceed with further evaluation of the lumen of the iliac vein and IVC. CT venography is supportive for further conformation, while venogram is the gold standard, with venography and IVUS mechanical thrombus removal and stent placement being performed in the same sitting. Anticoagulants are the mainstay of medical therapy for the management of such cases. Surgical options are reserved for refractory failure cases.

Financial support and sponsorship

Nil.

Conflicts of interest

There are no conflicts of interest.