Differential Beyond Deep Vein Thrombosis for Unilateral Leg Swelling: A Case of May-Thurner Syndrome in the Emergency Department

When patients present with unilateral leg swelling, a few top differential diagnoses come to mind. Most of these patients, at least at our shop, obtain ultrasound imaging during the triage process.

Since almost 1 million cases of deep vein thrombosis (DVTs) are diagnosed each year in the United States, it can be an easy diagnosis to make at the door.³ However, when the ultrasound is negative, how does your differential diagnosis evolve? We present a case of an elderly female with unilateral leg swelling that was diagnosed with symptomatic May-Thurner syndrome.

CASE REPORT

A 93-year-old female with a medical history of dementia, aortic stenosis status post transcatheter aortic valve replacement (TAVR), hypertension, hyperlipidemia, and a known pancreatic mass of unknown etiology presented to the emergency department with 10 days of left leg swelling. She reported pain only with palpation. She had been able to ambulate without difficulty. She denied any trauma, recent falls, recent travel, shortness of breath, or chest pain. She reported mild relief with elevation of her extremity. She had been compliant with her medications – one of which was a diuretic – and had no recent changes in her medications. She denied any personal or family history of clotting or bleeding disorders.

Her initial vital signs revealed a temperature of 97.8^oF, HR 66 bpm, BP 143/62, RR 18 breaths per minute, and 97% saturation on room air. She was well-appearing on exam, in no acute distress, with pertinent positives of chronic venous insufficiency changes to her bilateral lower extremities, more pronounced on the left along with asymmetric pitting edema, increased on the left. She had no cardiac murmurs and her breath sounds were clear without rhonchi or wheezing. Her abdomen was soft, non-tender, and non-distended.

She was found to have quite unremarkable complete blood count and basic metabolic panel except for a bicarbonate of 33 mmol/mL. Other notable findings were hemoglobin of 13.4 g/dL, sodium of 142 mmol/mL, creatinine of 0.88 mg/dL, NT-proBNP 10,707 pg/mL (normal range of those greater than 75 years old of 0-1,800 pg/mL), and d-dimer of 631 ng/mL DDU (d-dimer unit) (normal age adjusted range less than 243 ng/mL DDU).

Imaging was obtained and a left lower extremity ultrasound revealed no evidence of DVT, a left-sided Baker’s cyst, and lower extremity edema. A computed tomography (CT) of the abdomen/pelvis with intravenous contrast revealed extrinsic compression upon the left common iliac vein by the right common iliac artery compatible with May-Thurner syndrome without visible thrombus of the left iliac or common femoral vein, severe atherosclerosis of the abdominal aorta and iliac arteries, along with associated asymmetric left lower extremity edema. Incidental findings on her CT imaging revealed trace bilateral pleural effusions and a 2-centimeter probable cystic pancreatic mass.

Vascular surgery was consulted given symptomatic findings of classic May-Thurner syndrome. After discussion of management options and consideration of her age, history of dementia, and relatively mild symptoms, her family opted for more conservative management including lower extremity elevation and compression stockings. She was able to ambulate in the ED without difficulty, given strict return precautions, and ultimately was discharged home.

DISCUSSION

May-Thurner syndrome, also known as iliac compression syndrome or Cockett syndrome, involves extrinsic compression of the left common iliac vein by the right common iliac artery against the lower lumbar spine.² It is typically diagnosed in female patients aged 25-50 years old. It is a diagnosis to consider in those with recurrent DVTs or those with asymmetric leg swelling without signs of DVTs on ultrasound as it has a prevalence of 20%.

Although initially thought to be genetic, it is thought to occur secondary to chronic irritation of the pulsatile iliac artery against the common iliac vein resulting in venous spurs.³ These spurs increase the risk of blood clots. Risk factors for this syndrome include female sex, severe dehydration, and scoliosis. They also include risk factors for hypercoagulability such as prolonged travel, recent surgery, immobilization, oral contraceptive use, and pregnancy. It is important to note that May-Thurner syndrome may or may not have blood clots at the time of diagnosis.¹

May-Thurner syndrome is typically diagnosed on CT venography. As clots more commonly occur in the iliofemoral junction, ultrasound of the legs can be negative and ultimately miss the diagnosis. The gold standard diagnosis is contrast venography with transvenous pressure measurements.¹ However, this typically only occurs pre-operative prior to vascular therapy.

Management includes several different modalities. Typical management is with full dose anticoagulation. Thereafter, consideration for thrombolysis or thrombectomy of the clot can be considered. Stent placement may occur with this based upon evaluation by interventional radiology or vascular surgery. Conservative management includes elevation of the extremity and compression stockings.⁵

DIFFERENTIAL

When considering unilateral leg swelling, it is important to not anchor on a diagnosis of DVT. DVTs are common, but it is also important to assess the patient and look for skin changes that may clue the clinician into diagnoses such as phlegmasia alba dolens or phlegmasia cerulea dolens, as these increase the acuity of the condition. These syndromes are caused by a large clot burden that can lead to an ischemic limb. Skin changes are also seen in cellulitis; however, this usually includes systemic symptoms as well. Cellulitis of the lower extremity will be associated with a source such as a wound of the feet or legs. In middle-aged to elderly patients, consider osteoarthritis or gout if the swelling overlies a joint. Leg swelling may be from a more systemic condition as well, such as heart failure. Although heart failure typically is symmetrical and bilateral, some patients may have unilateral, asymmetric leg swelling. Finally, as in our patient, we were most concerned for abdominal cancer/metastases. Diseases within the pelvis that can compress blood flow to the legs are important to consider as it may be missed on initial examination and work-up.

TAKE-HOME POINTS

Although May-Thurner should be included in your differential diagnosis of unilateral leg swelling, be sure to keep in mind other causes as well, as the case is not always a DVT.

Our case was unique in several aspects.

• First, she is the oldest patient per literature review with a diagnosis of May-Thurner syndrome. The second oldest was diagnosed at the age of 91 years old.²
• Second, visualization of her May-Thurner syndrome was seen on CT scans since 2009 but was not interpreted as such by radiology, and she remained asymptomatic during that time.
• Third, her daughter had been diagnosed with May-Thurner syndrome while she was in her 50-60s. This is not thought to be a hereditary disease.
• Our patient had an exceptional case of May-Thurner syndrome given her unique aspects and few risk factors for predisposition.

REFERENCES

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6. Righini M, Van Es J, Den Exter P., et al. Age-Adjusted D-Dimer Cutoff Levels to Rule Out Pulmonary Embolism: The ADJUST-PE Study. JAMA. 2014;311(11):1117–1124.