A rare emergency department diagnosis of May-Thurner syndrome

Venous thromboembolism (VTE) is a frequent and serious emergency department (ED) diagnosis. When clinical risk stratification tools do not adequately explain the patient's presentation, physicians must consider less common underlying causes.

A 76-year-old male with chronic venous stasis presented to the emergency department with progressive bilateral leg swelling (left greater than right) and shortness of breath over one month, with acute worsening over 3 days. He was found to have pronounced asymmetric lower extremity edema and a new oxygen requirement. CT pulmonary angiography was notable for right-sided segmental pulmonary emboli with pulmonary infarction. Subsequent imaging with CT venography revealed the diagnosis of May-Thurner syndrome (MTS), characterized by left common iliac vein compression between the right common iliac artery and lumbar spine. The patient underwent successful catheter-directed thrombectomy and iliac vein stenting with restoration of venous flow.

MTS is a rare cause of deep venous thrombosis within the general population and can lead to severe morbidity. Diagnosis can be particularly challenging in atypical presentations that fall outside the typical 30-50-year-old female demographic. Progressive unilateral or asymmetric bilateral lower extremity swelling with left predominance, particularly in patients without classic VTE risk factors, should prompt consideration of underlying anatomical causes and advanced imaging such as CT venography or conventional venography.

MTS should remain in the differential for an emergency medicine physician when the clinical presentation reveals progressive asymmetric lower extremity swelling with left predominance. Absence of classic VTE risk factors and atypical demographic presentation does not eliminate the diagnosis.