A popliteal artery aneurysm is a bulging (

aneurysm An aneurysm is an outward bulging, likened to a bubble or balloon, caused by a localized, abnormal, weak spot on a blood vessel wall. Aneurysms may be a result of a hereditary condition or an acquired disease. Aneurysms can also be a nidus (s ...

) of the

popliteal artery The popliteal artery is a deeply placed continuation of the femoral artery opening in the distal portion of the adductor magnus muscle. It courses through the popliteal fossa and ends at the lower border of the popliteus muscle, where it branches ...

. A PAA is diagnosed when a focal dilation greater than 50% of the normal vessel diameter is found (the normal diameter of a popliteal artery is 0.7-1.1 cm). PAAs are the most common aneurysm of peripheral vasculature, accounting for 85% of all cases. PAAs are bilateral in some 50% of cases, and are often (40-50%) associated with an abdominal aortic aneurysm. Popliteal aneurysms are rarely symptomatic; they are typically discovered during routine

physical examination In a physical examination, medical examination, or clinical examination, a medical practitioner examines a patient for any possible medical signs or symptoms of a medical condition. It generally consists of a series of questions about the patien ...

s. The cause of these aneurysms is unknown, but they are more common in older people and men and occur in both legs about 50% of the time.

Presentation

PAAs are most often asymptomatic.Chronic symptoms are most often secondary to the

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exerted upon adjoining structures by the aneurysm (e.g. pain and

paresthesia Paresthesia is an abnormal sensation of the skin (tingling, pricking, chilling, burning, numbness) with no apparent physical cause. Paresthesia may be transient or chronic, and may have any of dozens of possible underlying causes. Paresthesias ar ...

s due to

tibial nerve The tibial nerve is a branch of the sciatic nerve. The tibial nerve passes through the popliteal fossa to pass below the arch of soleus. Structure Popliteal fossa The tibial nerve is the larger terminal branch of the sciatic nerve with root val ...

compression, calf swelling due to compression of the

popliteal vein The popliteal vein is a vein of the lower limb. It is formed from the anterior tibial vein and the posterior tibial vein. It travels medial to the popliteal artery, and becomes the femoral vein. It drains blood from the leg. It can be assess ...

Thrombosis Thrombosis (from Ancient Greek "clotting") is the formation of a blood clot inside a blood vessel, obstructing the flow of blood through the circulatory system. When a blood vessel (a vein or an artery) is injured, the body uses platelets (thro ...

within the aneurysm and subsequent luminal narrowing may result in

claudication Claudication is a medical term usually referring to impairment in walking, or pain, discomfort, numbness, or tiredness in the legs that occurs during walking or standing and is relieved by rest. The perceived level of pain from claudication can be ...

of gradual onset, while an acute thrombosis (occluding the vessel at the side of the aneurysm or lodging distally as the vessel narrows) may lead to acute lower extremity ischaemia and associated symptomatology (pain, paresthesia, paresis, pallor, poikilothermia). Thrombotic occlusion of distal vessels may result in blue toe syndrome, and

acrocyanosis Acrocyanosis is persistent blue or cyanotic discoloration of the extremities, most commonly occurring in the hands, although it also occurs in the feet and distal parts of face.Kurklinsky AK, Miller VM, Rooke TW. "Acrocyanosis: The Flying Dutchm ...

. Untreated, some 30% of those affected develop acute thrombosis and distal

embolization Embolization refers to the passage and lodging of an embolus within the bloodstream. It may be of natural origin (pathological), in which sense it is also called embolism, for example a pulmonary embolism; or it may be artificially induced (t ...

, risking potential limb loss. In cases with acute thrombosis/embolism, amputation rate is 15%.

Risk factors

Risk factors predisposing to the development of a PAA include: tobacco smoking, atherosclerosis, connective tissue disorders (e.g. Marfan syndrome, and Ehlers-Danlos syndrome), advanced age (peaking in the 6th to 7th decade of life), male gender, White race, and a family history of aneurysm.

Pathophysiology

A PAA seldom presents with a size greater than 5cm as symptoms typically develop before the aneurysm reaches such a size. Unlike aneurysms elsewhere in the body, the typical course of PAAs is to

embolize An embolism is the lodging of an embolus, a blockage-causing piece of material, inside a blood vessel. The embolus may be a blood clot (thrombus), a fat globule (fat embolism), a bubble of air or other gas (gas embolism), amniotic fluid (amnio ...

and produce ischaemia, rather than to progress to rupture.

Diagnosis

The popliteal fossa is to be examined bilaterally with the knee in a semi-flexed position. In some 60% of cases, the popliteal aneurysm presents as a palpable pulsatile mass at the level of the knee joint.

Doppler ultrasonography Doppler ultrasonography is medical ultrasonography that employs the Doppler effect to perform imaging of the movement of tissues and body fluids (usually blood), and their relative velocity to the probe. By calculating the frequency shift of ...

is the preferred diagnostic method. CT and MR angiography may also be employed.

Differential diagnosis

Differential diagnoses include; popliteal cyst, adventitial cyst,

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varicose vein Varicose veins, also known as varicoses, are a medical condition in which superficial veins become enlarged and twisted. These veins typically develop in the legs, just under the skin. Varicose veins usually cause few symptoms. However, some indi ...

Treatment

It is unclear whether

stent In medicine, a stent is a metal or plastic tube inserted into the lumen of an anatomic vessel or duct to keep the passageway open, and stenting is the placement of a stent. A wide variety of stents are used for different purposes, from expandab ...

ing or open surgery is a better for those with aneurysms that are not causing symptoms.

References

Diseases of arteries, arterioles and capillaries {{circulatory-stub