A 40-year-old woman with sickle cell trait presents to the emergency department with complaints of left lower limb pain and swelling that started 3 days ago. She is an active smoker for the last 15 years and smokes a pack per day. She occasionally takes omeprazole for gastroesophageal reflux disease symptoms. She has a history of anaphylactic shock that occurred 1 year ago. She denies any recent long-distance travel, surgery requiring immobilization, insect bite or the use of oral contraceptives. She states that her work requires her sitting for approximately 10 hours per day, with only a few breaks. Her vital signs at the emergency department are: 121/60 mmHg, 99.7°F, 96 bpm, 15 respirations per minute and 98% blood O2 saturation. Electrocardiogram and arterial blood gases are normal. Physical examination reveals a tender left thigh/calf, edema, warmth, and redness. Duplex ultrasound detects an extensive deep venous thrombosis from the left common iliac to popliteal vein. Thrombophilia screening detects no abnormalities. The patient is treated with low molecular weight heparin and is discharged on warfarin. After 1 week, she returns to the emergency department because of recurrent pain in her left leg, despite treatment with warfarin. The patient is treated with thrombolysis, and subsequent intravascular ultrasound demonstrates a severe left common iliac vein stenosis from a venous spur. The following day a stent is placed in the stenotic lesion and the patient shows clinical improvement. After 3 days of hospitalization, the patient is discharged home on warfarin for at least 6 months.
Which is the cause of deep venous thrombosis in this patient?
Show Answer
The correct answer is: D. Anatomic variant
The patient presents to the emergency department with left lower limb pain and edema, indicating acute deep venous thrombosis. An intravascular ultrasound detects a severe stenosis of the left common vein caused by a venous spur. This imaging finding is suggestive of May-Thurner syndrome.
May-Thurner syndrome is caused by venous outflow obstruction due to extrinsic compression. Usually the right common iliac artery compresses the left common iliac vein hindering normal blood flow. This predisposes to thrombus formation and eventually a deep venous thrombosis occurs.1,2
Patients with this syndrome are more often women aged 20-50 years old and present with recurrent leg pain, swelling and warmth. Venous stasis ulcers and skin discoloration may also occur.2 Treatment with low molecular weight heparin and oral anticoagulants is usually inadequate, and patients's symptoms recur in the next days. A venous duplex U/S detects the presence of venous thrombosis, but intravascular ultrasound during thrombolysis and venogram with contrast are the "gold standard" diagnostic tools. In the presence of deep venous thrombosis, the treatment includes a catheter-directed thrombolysis, followed by endovascular balloon dilation and/or self-expanding stent placement in order to prevent recurrent future thrombosis.1,2
Smoking (Answer A) and sedentary work (Answer B) are common risk factors for deep venous thrombosis. Smoking cessation and avoidance of prolonged sitting are recommended for patients that had an episode of deep venous thrombosis or are at high risk for having one. However, the recurrence of patient's symptoms and the "venous spur" identified by the intravascular ultrasound make May-Thurner syndrome a more likely cause of patient's symptoms.
Sickle cell trait (Answer C) is a benign asymptomatic condition and is not associated with the classic symptoms of sickle cell anemia. Therefore, deep venous thrombosis is unlikely to be caused by sickle cell trait.
Educational Objective
May-Thurner syndrome is a rare cause of deep venous thrombosis, however its prevalence is underestimated among population. The primary cause is the extrinsic compression of left common iliac vein from the overlying right common iliac artery with subsequent venous outflow obstruction. Intravascular ultrasound reveals the sign of "venous spur" within the left common iliac vein.1,2
References
Mousa AY, AbuRahma AF. May-Thurner syndrome: update and review. Ann Vasc Surg 2013;27:984-95.
Demir MC, Kucur D, Cakir E, et al. May-Thurner syndrome: a curious syndrome in the ED. Am J Emerg Med 2016;34:1920.e1-3.
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