Surgical Treatment of an Infected Popliteal Artery Aneurysm 12 Years after Aneurysm Exclusion and Bypass
Article Outline
The presence of persistent blood flow in popliteal artery aneurysms that have been treated with exclusion and bypass is surprisingly common. Complications from incompletely excluded aneurysms include aneurysm enlargement, local compressive symptoms, and sac rupture. Infection of a previously excluded and bypassed popliteal artery aneurysm is a notably rare complication. In this case report, we describe a patient with an infection of a popliteal artery aneurysm 12 years following surgical repair. The patient was successfully treated with aneurysm resection and soft tissue debridement.
Popliteal artery aneurysms account for nearly 70% of peripheral arterial aneurysms (PAAs).1 To avoid thrombosis, distal embolization, or rupture, surgical repair is typically recommended for symptomatic PAAs, asymptomatic aneurysms greater than 2
cm in diameter or those with mural thrombus.2 Outcomes following exclusion and bypass procedures are favorable, but persistent blood flow in the aneurysm sac has been documented in up to one-third of patients following PAA repair.3, 4, 5, 6, 7, 8, 9
We report an aneurysm infection more than a decade following bypass and exclusion. To our knowledge, there has been only one similar case report published in the English literature.10
Case Report
A 59-year-old man with a history of smoking, hypertension, and diffuse aneurysmal disease presented to an outside institution with a 2-week history of fevers, left popliteal fossa pain, and swelling. His surgical history included an urgent left femoroposterior tibial artery bypass 12 years earlier and an elective right femoroposterior tibial artery bypass 11 years earlier. Although the precise operative details of those procedures are unknown, both were performed for popliteal aneurysmal disease and involved the use of an autogenous venous conduit.
Given the patient's clinical findings and a leukocytosis on presentation, he was admitted and placed on intravenous antibiotics. An ultrasound (US) of the left popliteal fossa revealed a large heterogeneous mass consistent with a partially thrombosed PAA. Follow-up computed tomography-angiography (CTA) confirmed the presence of a partially thrombosed left PAA and revealed a contrast blush within the aneurysm sac (Fig. 1). Over the next week, he remained febrile despite negative blood, urine, and sputum cultures. Further investigation into his medical history suggested that he was immunocompetent, with no history of opportunistic infections or steroid use. He did not have any obvious predisposing factors for infection, such as recent travel or a history of intravenous drug use, dental disease, HIV infection, or prosthetic device implantation. A transthoracic echocardiogram was also negative for valve vegetations. He was transferred on the 10th hospital day to the medical service at our institution.
Fig. 1
Axial CT image of the lower extremities reveals a left popliteal artery aneurysm and a contrast blush within the aneurysm sac. Patent bilateral bypass grafts are visible within the subcutaneous tissue. A significant amount of soft tissue stranding is present within the perianeurysmal tissues.
During his 4-day hospitalization at our institution, his fever abated and his left popliteal swelling and pain improved with nonsteroidal anti-inflammatory treatment. Magnetic resonance imaging and angiography of his brain, chest, abdomen, and pelvis revealed no suspicious foci of infection. A repeat US of his left popliteal fossa confirmed the presence of an 8.9×3.5×4.5cm mass with minimal associated arterial flow consistent with a partially thrombosed PAA (Fig. 2). A surgical consultant recommended conservative treatment given the resolution of his symptoms and the presence of palpable graft and pedal pulses.
Fig. 2.
A transverse duplex ultrasound image shows an 8.9
×3.5×4.5cm popliteal artery aneurysm with flow present within the sac.
Four weeks later, he presented to the vascular surgery clinic with recurrent fevers, left popliteal pain, and decreased left knee mobility. On physical examination, his left popliteal fossa and calf were edematous and tender to palpation. His left popliteal pulse was palpable, while his right was absent. Bilateral lower extremity bypass graft and pedal pulses were strongly palpable. Due to concerns for an infected PAA, he was admitted to the vascular surgery service and begun on intravenous antibiotic therapy. Admission laboratory values, including chemistries and a complete blood count, were unremarkable. Initially, his fevers abated and his pain improved. However, several days into his admission, he reported increased pain and developed recurrent fevers.
On the seventh hospital day, he underwent operative exploration in the prone position via an “S”-shaped incision through the popliteal fossa. There was no evidence of aneurysm sac rupture. Purulent material was immediately encountered upon opening the sac. One patent geniculate branch that was actively bleeding into the aneurysmal sac was identified and ligated from within the aneurysm sac. After debridement of the perianeurysmal soft tissue, the sac was excised and the popliteal artery inflow and outflow were oversewn. The operative field was irrigated and the wound was closed over a Jackson-Pratt drain. His postoperative course was uneventful, and he was discharged home on the fourth postoperative day. Intraoperative cultures grew methicillin-sensitive Staphylococcus aureus, for which he received a 10-day course of cephalexin. The primary source of infection remains indeterminate. Final analyses of his blood, urine, and sputum cultures; transthoracic echocardiogram; and CT scans of his chest, abdomen, and pelvis were all unrevealing. On follow-up 22 months after surgery, he remained well, with no recurrent symptoms or functional limitations.
Discussion
Nonoperative management of PAAs is associated with a high incidence of complications, including thromboembolism, rupture, venous or nerve compression, and limb loss.11, 12 The most commonly performed surgical procedure for PAA is exclusion and bypass, which involves proximal and distal ligation of the aneurysm sac in combination with a reversed saphenous vein bypass graft.
A number of recent reports have highlighted the risk of persistent blood flow in the “excluded” aneurysm sac following exclusion and bypass. Jones et al.3 published one of the first such studies characterizing the consequences of incomplete exclusion. Among 36 excluded PAAs in their report, 33% enlarged over the 4-year follow-up period. Twenty-five percent of patients with enlarging aneurysms had compressive symptoms, and on duplex assessment, five patients had aneurysms that were fed by patent arterial side branches; all five were associated with significant growth of the aneurysm sac.
Ebaugh et al.4 reported similar results in a study of 41 patients undergoing 57 ligation and bypass procedures over a 13-year period. Thirty-two percent of aneurysms increased in size over a mean follow-up period of 4 years. Of the 16 patients who underwent subsequent examination with CTA or duplex ultrasound, flow was identified in 75% of excluded sacs, although it did not correlate with increased aneurysm size. The authors concluded that PAA excision or endoaneurysmorraphy should be performed when technically feasible.
In 2004, Kirkpatrick et al.5 noted a comparable pattern in 36 limbs that underwent ligation and bypass over a 10-year period. During a mean follow-up period of 4 years, residual blood flow in the PAA sac was seen in 33% of patients. Two-thirds of these patients had aneurysm sacs that increased in size and half (6 of 12) were symptomatic. Five of the 6 symptomatic patients underwent repair via a posterior approach (1 for rupture). Collateral vessels feeding the aneurysm sac were identified and ligated in all 6 cases. Endoaneurysmorraphy via a posterior approach, oversewing of side-branches, and onlay grafting were recommended as an alternative to traditional ligation and bypass.
Since Kirkpatrick's review, several studies have further characterized the incidence of incomplete exclusion following PAA repair. Deglise et al.6 reported that 24% of excluded aneurysms demonstrated residual flow on multislice CT, while Mehta et al.7 found persistent flow in 38% of aneurysm sacs following 26 PAAs repaired via a medial approach. Twenty-three percent of aneurysms increased in size and 12% ruptured. Davies et al.8 reported a 15% rate of persistent flow following ligation and bypass and found that two of five patients required reoperation for rupture or local symptoms. In the largest review published to date, Ravn et al.9 observed a 33% rate of aneurysm expansion following medial repair of over 700 PAAs.
Our review of the English literature revealed only one similar case report of an infected PAA following an exclusion and bypass procedure. That case involved a 65-year-old man who presented with fevers, right popliteal fossa swelling, and a thrombosed 3.5cm PAA on CT 2 years after his initial PAA repair.10 He required subsequent resection of his aneurysm. Thrombus and aneurysm sac cultures were negative, although blood cultures grew Campylobacter fetus.
In conclusion, studies have consistently demonstrated that up to one-third of patients have incomplete PAA isolation following standard exclusion and reconstructive bypass techniques. Such patients are at risk for aneurysm enlargement, local compressive symptoms, and even sac rupture. PAA infection rarely occurs after an exclusion and bypass procedure but should be considered in any patient with evidence of local or systemic infection. When a PAA infection is diagnosed, aneurysm excision, debridement, reconstruction with autogenous conduit, and intravenous antibiotic therapy are recommended.
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PII: S0890-5096(09)00339-2
doi:10.1016/j.avsg.2009.09.016
© 2010 Published by Elsevier Inc.
