Overview
Definition:
A popliteal artery aneurysm (PAA) is a localized, permanent dilation of the popliteal artery, typically defined as a diameter greater than 1.5 times the adjacent normal artery or exceeding 2 cm.
Epidemiology:
PAAs are the most common peripheral arterial aneurysms, accounting for 70% of all peripheral aneurysms
They are strongly associated with abdominal aortic aneurysms (AAAs), occurring in 40-50% of patients with AAAs
The incidence is higher in men and older individuals, particularly those with atherosclerotic risk factors like smoking, hypertension, and hyperlipidemia
Spontaneous rupture is rare but associated with high morbidity and mortality.
Clinical Significance:
PAAs pose a significant risk of limb-threatening complications, including thrombosis, distal embolization leading to acute limb ischemia, and, rarely, rupture
Prompt diagnosis and appropriate management are crucial to prevent devastating outcomes and preserve limb function for surgical residents preparing for DNB and NEET SS examinations.
Clinical Presentation
Symptoms:
Asymptomatic presentation is common, discovered incidentally
Symptomatic presentation may include: Pulsatile mass in the popliteal fossa
Pain in the calf or foot, often exacerbated by activity (claudication)
Acute limb ischemia due to thrombosis or embolization, characterized by sudden onset of severe pain, pallor, pulselessness, paralysis, and poikilothermia
Rest pain, non-healing ulcers, or gangrene in severe cases.
Signs:
A palpable, expansile pulsatile mass in the popliteal fossa, best appreciated with the knee extended and the patient prone
Diminished or absent distal pulses (dorsalis pedis, posterior tibial)
Signs of acute limb ischemia if thrombosed or embolized
Neurological deficits if peroneal nerve is compressed by the aneurysm.
Diagnostic Criteria:
No specific diagnostic criteria exist, but a diagnosis is typically made based on imaging findings
A diameter >2 cm in the popliteal artery, or a >50% increase compared to the adjacent segment, is generally considered aneurysmal
For surgical intervention, a threshold diameter of 2 cm is often used, or symptomatic aneurysms regardless of size.
Diagnostic Approach
History Taking:
Detailed history of cardiovascular risk factors: smoking, hypertension, diabetes mellitus, hyperlipidemia, coronary artery disease, previous AAA
History of claudication or rest pain
Any symptoms suggestive of acute limb ischemia
Family history of aneurysms
Previous vascular interventions.
Physical Examination:
Careful palpation of the popliteal fossa for a pulsatile mass
Auscultation for bruits over the mass
Assessment of distal pulses in the lower extremities (femoral, popliteal, dorsalis pedis, posterior tibial)
Neurological examination of the foot and lower leg
Assessment for signs of peripheral neuropathy or ischemia.
Investigations:
Duplex ultrasonography (USG): The primary non-invasive imaging modality for diagnosis and surveillance
It can accurately measure aneurysm diameter, assess flow patterns, and detect thrombus
Computed tomography angiography (CTA): Provides detailed anatomical information, useful for planning surgical or endovascular repair, especially for complex anatomy or suspected complications
Magnetic resonance angiography (MRA): An alternative to CTA, useful in patients with contrast allergies or renal dysfunction
Arteriography: Historically used but now less common as a primary diagnostic tool
may be used intraoperatively or for planning complex interventions.
Differential Diagnosis:
Baker's cyst (popliteal cyst): Can mimic a pulsatile mass but lacks true expansile pulsation and is often associated with underlying knee pathology
Femoral artery aneurysm: May be confused if palpation is not meticulous
Lymphadenopathy: Usually firm and non-pulsatile
Arteriovenous fistula: Presents with a palpable thrill and continuous bruit.
Management
Indications For Intervention:
Symptomatic aneurysm: Acute limb ischemia, nerve compression, rupture
Asymptomatic aneurysm: Diameter >2.0 cm, or associated with significant risk factors for complications
Aneurysm with thrombus, especially if protruding or mobile
Association with distal embolization.
Surgical Management:
Open surgical repair: The traditional gold standard
Typically involves ligation of the aneurysm and bypass grafting using autogenous saphenous vein or prosthetic material (e.g., PTFE)
The aneurysm sac is either excised or excluded
Key steps include proximal and distal control of the popliteal artery, thrombectomy, and graft placement
Endovascular repair (EVAR): Increasingly used, especially for patients unsuitable for open surgery
Involves deployment of a stent-graft to exclude the aneurysm sac from circulation
Typically accessed via transfemoral approach
Requires suitable aneurysm anatomy for stent-graft sealing.
Preoperative Preparation:
Thorough cardiovascular assessment and optimization
Risk stratification for anesthesia and surgery
Optimization of comorbidities (hypertension, diabetes)
Smoking cessation advice
Preoperative duplex ultrasound and/or CTA to delineate anatomy and plan the approach
Antibiotic prophylaxis.
Postoperative Care:
Close monitoring for signs of bleeding, infection, or graft occlusion
Pain management
Early mobilization
Antithrombotic therapy (aspirin, clopidogrel) as per protocol
Serial duplex ultrasound surveillance to assess graft patency and monitor for endoleaks (in EVAR).
Supportive Care:
Management of risk factors (smoking cessation, statin therapy, antihypertensives)
Wound care
Pain control
Deep vein thrombosis prophylaxis
Nutritional support.
Complications
Early Complications:
Graft thrombosis or occlusion
Distal embolization
Acute limb ischemia
Bleeding from suture lines or graft
Infection of the graft
Nerve injury (e.g., peroneal nerve palsy)
Deep vein thrombosis.
Late Complications:
Graft degeneration or pseudoaneurysm formation
Distal embolization from thrombus within the aneurysm sac (if not completely excluded)
Stenosis or occlusion of the graft
Chronic limb ischemia
Endoleak (in EVAR).
Prevention Strategies:
Meticulous surgical technique, including adequate graft length and securing, proper suture techniques, and careful handling of the artery
Use of autogenous vein for bypass when possible
Appropriate antithrombotic therapy
Careful patient selection for EVAR and appropriate stent-graft sizing
Aggressive surveillance with duplex ultrasound.
Prognosis
Factors Affecting Prognosis:
Presence and severity of limb ischemia
Patient's overall health and comorbidities
Success of the repair (graft patency)
Promptness of diagnosis and intervention
Type of repair (open vs
endovascular).
Outcomes:
Successful repair leads to excellent limb salvage rates
Open repair generally has high long-term patency and durability
Endovascular repair offers a less invasive option with good short- to mid-term results, but long-term durability may be lower than open repair, especially in certain anatomies
Unrepaired symptomatic aneurysms have a high risk of limb loss.
Follow Up:
Regular clinical and duplex ultrasound follow-up is essential
For open repair, annual follow-up is typically recommended to monitor graft patency
For EVAR, more frequent follow-up is required initially to detect endoleaks and monitor graft integrity, usually with duplex ultrasound and potentially CTA or MRA
Follow-up should continue for the lifetime of the patient.
Key Points
Exam Focus:
Popliteal aneurysms are the most common peripheral aneurysms and are strongly associated with AAAs
Management is indicated for symptomatic aneurysms or asymptomatic aneurysms >2 cm
Duplex US is the primary diagnostic tool
Management options include open surgical repair with bypass and endovascular exclusion.
Clinical Pearls:
Always palpate the popliteal fossa in patients with peripheral vascular disease or AAA
Suspect popliteal aneurysm if a pulsatile mass is found
Differentiate from Baker's cyst based on pulsation
Endovascular repair requires careful anatomical assessment for suitability.
Common Mistakes:
Failure to adequately assess distal pulses
Mistaking a Baker's cyst for a popliteal aneurysm
Inadequate imaging leading to poor surgical planning
Not providing adequate antithrombotic therapy post-repair
Insufficient long-term surveillance for graft issues or endoleaks.