CASE 8013 Published on 22.11.2009

Incidental finding of a giant popliteal aneurysm on MRI of the knee

Section

Cardiovascular

Case Type

Clinical Cases

Authors

Schubert R.
Radiologie am Europa-Center, Berlin, Germany.

Patient

64 years, male

Clinical History
This is a report of a 64 year old man, who obtained an MRI of the left knee for chronic joint pain and a mass in the back of the knee first mistaken for a popliteal cyst.
Imaging Findings
A 64 year old man was scheduled for an MRI of the left knee for arthralgia and a mass in the back of the knee which had been bothering him for several months. His family physician suspected the presence of a Baker cyst. Although moderate osteoarthritis was present in the joint, the semi-membranosus gastrocnemius bursa was not enlarged and showed only minimal fluid content. In the centre of the popliteal fossa, MRI showed a fusiform, thick-walled mass measuring 5x4x9 cm, with alternating hypo- and hyperintense signal characteristics (Fig. 1). Transverse sections showed different signal layers arranged in an concentric fashion and a small eccentric flow void (Fig. 2). On sagittal sections, the mass could be followed into the popliteal artery (Fig. 1b). The foot was warm and foot pulses were palpable. The patient was referred to a vascular surgery unit, where the aneurysm was treated with a by-pass / ligation procedure with excision of the aneurysmal sac.
Discussion
Popliteal aneurysms account for up to 70% of all peripheral arterial aneurysms. They are associated with aneurysmal disease elsewhere in the body and are bilateral in over half of cases. The most common aetiology is arteriosclerosis, whereas trauma and infections contribute only to a to a small percentage. The mean presentation age is 68. One third of all patients are asymptomatic. The most typical complication is acute thrombosis and/or peripheral embolism. Popliteal aneurysm rupture is rare, but life-threatening and leads to limb loss in up to 67% of cases. In huge aneurysms, the mass effect may also lead to neuralgia, paresis, and venous congestion. The management of popliteal aneurysms depends on several factors like configuration and size of the aneurysm, inflow and outflow, presence or absence of embolism or signs of rupture. In smaller aneurysms, open and endovascular treatment strategies have proved equally effective. Extremely large aneurysms causing mechanical problems, like in this case, need operative decompression and often by-pass surgery. In long-standing thrombotic occlusion of popliteal aneurysms, collateral circulation may influence the operative strategy to a certain extent. Case reports about the use of MRI or MR angiography in large popliteal aneurysms are sporadic, but the usefulness of these methods is beyond doubt. However, colour-coded Doppler US can establish the diagnosis of superficial aneurysms more efficiently, and an arteriography may still be performed during the interventional or surgical session.
Differential Diagnosis List
Giant popliteal artery aneurysm with a concentric parietal thrombus
Final Diagnosis
Giant popliteal artery aneurysm with a concentric parietal thrombus
Case information
URL: https://www.eurorad.org/case/8013
DOI: 10.1594/EURORAD/CASE.8013
ISSN: 1563-4086