May–Thurner syndrome: an overlooked cause of venous thromboembolism

To the Editor: The recent article by Akram and Sadashiv1 presents a timely and most welcome opportunity to enhance awareness, in the medical community at large, of the investigation and treatment options for proximal deep vein thrombosis (DVT) of the lower extremity.

Diagnosis of lower extremity DVT is generally made or confirmed with duplex ultrasound assessment. Standards in Australia and New Zealand state that duplex ultrasound for DVT should determine the proximal extent of the thrombus, as well as identify structures causing extrinsic compression that may have contributed to the thrombosis.2 This information assists the clinician in determining the need to consider specific treatments, such as venous stenting for May–Thurner syndrome or placement of a caval filter in cases where there is a free‐floating thrombus in the inferior vena cava. Duplex ultrasound can play a key role in the diagnosis of May–Thurner syndrome.3

Technical factors, such as the presence of bowel gas, may inhibit ultrasonographic views of the abdominal and pelvic vasculature, and may therefore prevent attainment of the required information. Further, clinical experience in vascular surgery services in Australia and overseas has shown that, despite the above‐mentioned standards, it is common for there to be no attempt to obtain adequate proximal views during ultrasound DVT scans. Clinicians should therefore be wary of the limitations of ultrasound DVT scans and consider alternate imaging modalities such as computed tomography venography in cases where ultrasound has yielded inadequate information.

Clinicians should also be aware of the potential of clot removal therapies such as catheter‐directed thrombolysis to improve long term outcomes for patients with proximal lower extremity DVT, whether or not May–Thurner syndrome is identified as a predisposing factor. Recent studies have reported improvements in the incidence and/or severity of post‐thrombotic syndrome in patients receiving catheter‐directed thrombolysis compared with those treated with anticoagulation alone.4,5 The appropriateness of catheter‐directed thrombolysis for some patients is acknowledged in the relevant guidelines,6 although patient selection remains a topic of debate.

Lower extremity DVT is a common condition encountered in both inpatient and community settings. Due to technical considerations and quality variations, ultrasound DVT scans do not always yield adequate information to determine the optimal therapeutic approach. In such situations, consultation with a vascular specialist is strongly encouraged.