Asymptomatic Huge Popliteal Pseudoaneurysm With 2 Internal Solid Thrombi
A 66-year-old woman was admitted to our hospital with acute inferior myocardial infarction. She had a history of hypertension, hyperlipidemia, and surgical replacement of the descending aortic aneurysm with a prosthetic graft at 59 years of age. Emergent coronary angiography showed 90% stenosis in the middle right coronary artery. The lesion was successfully dilated with the deployment of a bare metal stent.
Physical examination revealed an absence of pulsation of the left popliteal artery and a slight swelling above the left popliteal fossa without pulsation and tenderness. The ankle-brachial pressure indexes of her right and left extremities were 1.08 and 0.58, respectively. Regardless of our careful history taking, she had no history of claudication, traumas, surgery, or acupuncture around the left knee joint. A computed tomography revealed a huge mass (65×70×50 mm) above the left knee joint (Figure 1A) and ruled out adjacent osteochondroma. Her left popliteal artery was obstructed just behind the mass (Figure 1B). Abundant collateral arteries were observed running around the mass and connecting into the distal part of popliteal artery. The mass had 2 high-density enhanced areas surrounded by an outer low-density area without enhancement (Figure 1C and 1D).
An aneurysmectomy was performed (Figure 2A), and the left popliteal artery was repaired with a 7-mm-diameter Dacron graft. A resected specimen had 2 internal solid thrombi surrounded by extensive thick blood with capsule (Figure 2B). The arterial perforation communicating with the aneurysmal sac was covered by the thrombus. Histologically, the wall of aneurysm lost elastic tissues in the media that were replaced by collagen fibers, indicating a pseudoaneurysm (Figure 2C). Rich capillary channels were observed in an old mural thrombus inside the aneurysm (Figure 2D).
A pseudoaneurysm of the popliteal artery is rare and mostly reported in association with penetrating trauma, adjacent osteochondroma, or iatrogenic complications such as total knee arthroplasty, arthroscopic meniscectomy, and acupuncture.1–3 In this case, none of the conceivable reasons listed above applied. However, spontaneous dissection of the arterial wall of patients with arteriosclerosis could be an initial trigger leading to repeated bleeding from the membranous capsule into the closed sac. Consequently, such a giant pulseless aneurysm may be formed with internal thrombus. To the best of our knowledge, this is the largest case of an asymptomatic popliteal pseudoaneurysm reported to date.