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Vascular » Peripheral Vascular
Popliteal artery aneurysm
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Presentation An 85 year old male presented to the hospital with an acute intracranial bleed, thought to be secondary to amyloidosis. While in the hospital, he complained of swelling of the right leg. An ultrasound was performed to rule out venous thrombosis. The distal peripheral pulses were normal.
 
 
 
Caption: Sagittal scan of the right popliteal region.
Description: Sagittal scan demonstrates an elongated solid mass with central hypoechoic component in the right popliteal fossa. The popliteal artery was not seen to be separate from this mass. The popliteal vein was normal.
 
 
 
Caption: Transverse scan of the right popliteal artery.
Description: Transverse view showing the mildly echogenic mass with central hypoechoic component.
 
 
 
Caption: Transverse color Doppler view.
Description: Transverse view demonstrates the central part of the mass to be vascular.
 
 
 
Caption: Sagittal color Doppler scan.
Description: Color Doppler demonstrating that the hypoechoic part fills with color and is the dilated proximal popliteal artery. Its distal part exiting the mass is normal. The popliteal vein [in red] appears to be compressed by the mass, but is patent.
 
 
 
Caption: Spectral Doppler study.
Description: Spectral Doppler study through the vascular part of the mass demonstrates an arterial waveform.
 
Differential Diagnosis Thrombosed right popliteal artery aneurysm, Baker’s cyst [but the color Doppler features effectively rule out this possibility], Pseudoaneurysm arising from the popliteal artery [but the popliteal artery is not seen seperate from the mass, so this most likely represents aneurysmal dilatation of the popliteal artery].
 
Final Diagnosis Partially thrombosed right popliteal artery aneurysm.
 
Discussion Popliteal artery aneurysms per se are not very common, but popliteal artery pseudoaneurysms are quite a common sequel to penetrating or blunt trauma, iatrogenic surgeries and procedures [rarely acupuncture] and adjacent bone tumors. Constant and repeated vascular wall trauma triggers the formation of the pseudoaneurysm. These vascular masses may present with pain and with palpable masses around the knee and may be pulsatile. If younger patients without a known history of trauma are diagnosed with popliteal artery aneurysms, underlying bone pathologies need to be ruled out as asymptomatic bone tumors may repeatedly irritate the popliteal artrey and present as popliteal artery aneurysms.

Many patients with true aneurysms are asymptomatic and these may be detected incidentally, owing to their accessibility to palpation. Atherosclerosis likely plays some role in pathogenesis. Usually a popliteal artery is considered aneurysmal when the diameter is 1.2 cm or larger, a definitive aneurysm when it is 2 cm or greater or if it is more than 1.5 times the caliber of the proximal popliteal artery. Thrombosed aneurysms when symptomatic are usually found to be larger [3 cm or more]. Complications of these aneurysms include rupture, thromboemboli, and flexion deformities of the leg. Once thrombosis sets in, which is the most common complication, morbidity increases considerably.

Lowell, et al in their study predicted aneurysm size greater than 2 cm, presence of thrombus and poor distal run-off as poor prognostic factors. The presence of these risk factors makes the patient an ideal candidate for an elective surgical treatment and prevents inadvertent amputations. Recent studies by Galland, et al have suggested 3 cm as the cut-off for the size of the aneurysm, after which intervention is needed.

Real time ultrasound and color Doppler imaging are the initial non-invasive diagnostic modalities used to evaluate popliteal artery aneurysms. A dilated artery or a vascular mass arising from the artery is identified. Pseudoaneurysms can be seen connected to the main popliteal vessel via a neck or tract, the demonstration of which is pathognomonic for a pseudo aneurysm. If an aneurysm contains thrombus, echogenic material is seen within, which may partially or completely occlude the cavity. The hemo-dynamics can be studied by color Doppler, which may demonstrate swirling flow within the aneurysm or no color flow if it is completely occluded. The neck of the pseudoaneurysm may show a to- and –fro movement. Very importantly, the presence of thrombosis, distal run-off and collaterals can be assessed, which have prognostic value for the effectiveness and outcome of surgery.

CT angiography, MR angiography and conventional angiography can all provide additional important preoperative information.
 
Case References 1.Lowell RC, et al. Popliteal artery aneurysms: the risk of nonoperative management. Ann Vasc Surg. 1994 Jan; 8(1): 14-23.
2.Dawson I, et al. Atherosclerotic popliteal aneurysm. Brit J of Surg 84(3), March 1997: 293-99.
3.Brzezinski T, et al. Supragenual popliteal artery pseudoaneursym in a patient with femoral bone exostosis. Case Rep Clin Pract Rev, 2003; 4(1): 43-45.
4.Atta HM, et al. Delayed presentation of popliteal artery pseudoaneurysm following blunt trauma. Am Surg. 1997 Jun; 63(6): 496-9.
5.Harman M, et al. Popliteal artery pseudoaneurysm: a rare complication of brucellosis. J Clin Ultrasound. 2004 Jan; 32(1): 33-6.
6.Harder Y, et al. Popliteal aneurysm: diagnostic workup and results of surgical treatment. World J Surg. 2003 Jul; 27(7): 788-92.
7.Galland, et al. Management of popliteal aneurysm. Brit J of Surg 2002, 89, 1382-85.

8.Ascher, et al. Small popliteal artery aneurysms: are they clinically significant? J Vasc Surg 2003 Apr; 37: 755-60.
 
Follow Up In view of his acute intracranial bleed, this patient was not started on anticoagulants and was scheduled for a limb angiography followed by elective repair of the aneurysm upon stabilization.
 
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