Nonatherosclerotic limb ischemia: Prompt evaluation and diagnosis

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ABSTRACTLimb ischemia is most often associated with atherosclerosis and older age. When a younger patient without risk factors for atherosclerosis presents with symptoms of limb ischemia, vascular occlusion may not be suspected initially, thus delaying diagnosis and treatment. Delayed diagnosis can lead to a poor outcome. Here, we describe several uncommon causes of limb ischemia and their initial presentations, workup, and treatment to help guide the practitioner in making a timely diagnosis in this unusual patient population.


  • A high index of suspicion should be maintained to recognize symptoms consistent with limb ischemia in a younger patient in the absence of the usual atherosclerosis risk factors.
  • A workup for most conditions includes noninvasive vascular ultrasonography to detect and quantify limb ischemia.
  • Prompt referral for surgical or endovascular treatment is necessary for optimal limb salvage.



Timely diagnosis of limb ischemia is critical to limb health and limb salvage. The cause in most cases is related to atherosclerosis, and patients with limb ischemia are usually older and have risk factors for atherosclerosis, such as smoking, diabetes, hypertension, hyperlipidemia, and coronary artery disease. When younger patients develop limb ischemia, the diagnosis is often delayed since the index of suspicion is quite low in the absence of the usual risk factors.

Here, we discuss several nonatherosclerotic causes of limb ischemia: popliteal artery entrapment syndrome, popliteal artery aneurysm, cystic adventitial disease, persistent sciatic artery, phlegmasia cerulea dolens, Buerger disease, Takayasu arteritis, arterial thoracic outlet syndrome, and external iliac endofibrosis (Table 1). Our goal is to help clinicians make a timely diagnosis and ultimately save the patient’s limb.


Figure 1. Computed tomography of the lower extremities shows right popliteal entrapment syndrome with distal runoff occlusions (A) and abnormal insertion of the gastrocnemius muscle (B, arrow) in the patient’s right leg. The left leg is normal. Intraoperative angiography shows a patent popliteal artery in the neutral position (C) with occlusion during forced dorsiflexion (arrow, D).

Popliteal artery entrapment syndrome occurs when the popliteal artery becomes compressed in the popliteal fossa, particularly during exercise.1,2 The underlying problem may be that the popliteal artery has an aberrant course lateral to the medial head of the gastrocnemius muscle, or the medial head of the gastrocnemius may have an abnormal insertion, or there may be fibrous bands in the popliteal fossa, or a combination of these (Figure 1).1–3 Functional popliteal artery entrapment syndrome occurs when there is compression of the artery without an anatomic cause.1–3

The classic clinical presentation is a young athletic patient with calf or foot claudication (crampy pain with exercise, relieved with rest), but other symptoms can include coldness, paresthesias, and numbness. Pain at rest and tissue loss are rare on presentation but may develop if the diagnosis and treatment are delayed.3

Continued compression and microtrauma to the artery may lead to an intramural hematoma, thrombus formation, aneurysmal degeneration, dissection, or even acute thrombosis.2 If the diagnosis is delayed, the patient’s condition may progress from intermittent arterial compression with plantar flexion to complete arterial thrombosis and critical limb ischemia, putting the patient at risk of limb loss.

Diagnosing popliteal artery entrapment syndrome

The diagnostic workup includes a detailed history with a focus on the cause of pain (usually exercise), a comprehensive physical examination that includes looking for wounds, and a thorough pulse examination.

The workup should start with noninvasive imaging such as duplex arterial ultrasonography with and without provocative measures (plantar flexion), the ankle-brachial index with and without provocative measures, and exercise treadmill testing with ankle-brachial index measurement.1,2 Plantar flexion may be necessary to elicit arterial compression that is usually absent at rest.

Magnetic resonance imaging (MRI) and computed tomography (CT) of the lower extremity are useful to identify an arterial abnormality and aberrant muscle anatomy1,3; MRI is currently the gold standard for delineating the muscles of the popliteal fossa.4 If these studies do not shed light on the diagnosis, arterial angiography with and without provocative maneuvers is useful in identifying compression of the popliteal artery.1–3

Treating popliteal artery entrapment syndrome

Treatment depends on the level of arterial injury.

For patients with symptoms but no evidence of arterial injury, the most common procedure offered is popliteal fossa decompression.1–3 This involves surgical release of the medial head of the gastrocnemius muscle and other muscles compressing the popliteal artery.

For patients with evidence of arterial injury such as stenosis, dissection, or aneurysm, bypass grafting may be required.

For patients who present with acute limb ischemia, both surgical thrombectomy with possible bypass and intraarterial lysis have been described.1,2,5


Figure 2. Partial thrombosis of the right popliteal artery aneurysm is seen on arterial duplex ultrasonography in grayscale (A) and with color flow (B) showing the flow lumen (red) and thrombus (arrow). Computed tomography of another patient (C, D) shows partial thrombosis of a right popliteal artery aneurysm (arrow) in transverse (C) and sagittal (D) views.

Popliteal artery aneurysm (Figure 2) is the most common type of aneurysm of the peripheral arteries of the lower extremity and is present in about 1% of men over age 65. Fifty percent are bilateral, and 50% are associated with an abdominal aortic aneurysm.6,7 While up to 80% patients with this type of aneurysm have no symptoms at the time of diagnosis, symptoms develop at a rate of 14% per year, with acute limb ischemia occurring in up to one-third of cases.6,7

When popliteal artery aneurysm progresses to acute limb ischemia, the consequences are often deleterious, as the tibial arteries distal to the popliteal artery are often occluded, limiting treatment options.

Popliteal artery aneurysm is defined as a local dilation of the artery of 2 cm or greater or an increase in the diameter to 1.5 times normal.6

Acute thrombosis of the aneurysm with limb ischemia is the most common presenting symptom and occurs in 50% of symptomatic cases of popliteal artery aneurysm.7 Almost 25% of patients present with intermittent claudication secondary to thrombosis, partial thrombosis with distal embolization, or combined aneurysmal and atherosclerotic disease. Compression of the popliteal vein by the popliteal artery aneurysm can cause leg swelling with or without deep vein thrombosis in up to 5% of patients.6 Rupture is very rare, with a rate of 2% to 4%.6,7

Diagnosing popliteal artery aneurysm

The diagnosis can be made with arterial duplex ultrasonography, which is also useful for follow-up surveillance.6–8 In the acute setting, computed tomographic angiography (CTA) or magnetic resonance angiography (MRA) is useful not only to identify the popliteal aneurysm, but also to define the distal tibial outflow vessels.6,7

Treating popliteal artery aneurysm

Management of an acutely thrombosed popliteal artery aneurysm starts with systemic anticoagulation with intravenous heparin, followed initially by arterial angiography and lysis.8–11 This approach has been shown to be safe and effective even in the absence of arterial runoff distal to the thrombosed popliteal aneurysm. Conversion to open thrombectomy and bypass can be done if initial lytic therapy fails, if the patient develops complications of lytic therapy, or if the patient needs emergency revascularization because of motor and neurologic deficits in the affected extremity.8,10,11

How to manage the asymptomatic patient depends on the size of the aneurysm. Most studies recommend 2 cm or larger as the criterion for repair,6–8,12 while others suggest treating even smaller aneurysms if thrombus is detected.9 Preoperative imaging before elective treatment of an asymptomatic popliteal artery aneurysm includes either CTA or MRA,8,10 which allows the surgeon to visualize the full extent of the aneurysm to best plan the surgical approach. Diagnostic angiography can help determine the most suitable bypass target and can better characterize tibial outflow.

Asymptomatic popliteal artery aneurysm has traditionally been treated with surgical bypass with exclusion of the aneurysm,6–8,12 but more recently, endovascular approaches using self-expanding stent grafts have been described. Further study is needed to determine the long-term efficacy of the endovascular approach.8,10


Cystic adventitial disease is a rare condition in which a blood vessel is narrowed due to mucin-containing cysts in the adventitia. More than 80% of cases occur in the popliteal artery, but it has been described in other peripheral arteries and veins.13,14 It is more common in men than in women and typically occurs in the 4th or 5th decade of life. Most patients present with the sudden onset of calf claudication without the usual risk factors for peripheral vascular disease.13

Diagnosing cystic adventitial disease

Noninvasive arterial or venous duplex ultrasonography can be a good screening tool, as the cysts appear hypoechoic, but results are operator-dependent. CTA and MRA are the imaging tests of choice, as they can detect the cystic lesions and define vessel anatomy for intervention. Diagnostic angiography does not show the cysts themselves but instead reveals a classic “hourglass” and “scimitar” pattern of arterial narrowing that suggests the underlying pathology.13,14

Treating cystic adventitial disease

Usual treatment is complete cyst resection and vessel reconstruction by surgical bypass. Other therapies include open surgical cyst evacuation and removal of the cyst wall, open surgical cyst aspiration, aspiration guided by ultrasonography or CT, and percutaneous angioplasty. However, these nonsurgical treatments have not been shown to be as effective and long-lasting as cyst excision and bypass.13,14


Figure 3. In this three-dimensional reconstruction of a computed tomographic scan (posterior view) in a patient with a left persistent sciatic artery, the arrow indicates dilation of an aneurysm.

Persistent sciatic artery is a rare developmental abnormality.15–17 Normally, as the femoral artery develops in the embryo, the sciatic artery involutes to form the inferior gluteal artery. But if the femoral system fails to mature, the sciatic artery, which is adjacent to the sciatic nerve posteriorly as it goes through the sciatic foramen, persists and functions as the major artery supplying the lower extremity, continuing to the posterior thigh and joining the popliteal artery (Figure 3).15,17

Persistent sciatic artery has an incidence of 2.5 to 4 per 10,000 per year15 and is bilateral in almost half of cases.16 Up to 40% of patients have no symptoms, but symptoms may develop by age 40 to 50. Because of repeated trauma to the vessel as it passes through the sciatic foramen,18 the persistent sciatic artery typically sustains accelerated atherosclerotic changes that make it susceptible to aneurysm formation,15 and up to 46% of patients present with aneurysmal degeneration.17

Classically, patients present with lower extremity ischemia from atherosclerotic changes in the persistent sciatic artery or aneurysmal degeneration and thromboembolism.15 Rarely, these aneurysms rupture.15,17 Other signs and symptoms include a pulsatile mass in the buttock, lower extremity numbness, motor weakness, and radicular pain along the sciatic nerve distribution from nerve compression.15–17

Physical findings vary but are distinguished by the lack of femoral pulses in the presence of pedal pulses. A pulsatile buttock mass with evidence of lower extremity nerve compression or limb ischemia or both is pathognomonic of a persistent sciatic artery aneurysm.16,18

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