Infra-Inguinal Aneurysms – Threat to Life and Limb?

Results: 39 patients (mean age 58.3yr, range 18-98), of which 27 were male, were identified (24 PseudoAneurysms (PA), 12 True Aneurysms (TA) and 3 Mycotic Aneurysms (MA)). The majority of the PAs were secondary to Intravenous Drug Abuse, IVDA (41%), followed by interventional procedures (29%), vascular anastomotic sites (13%), orthopaedic surgery (13%) and penetrating trauma (4%). 11/12 (92%) TAs were popliteal in origin, with 22/24 (92%) of PAs located at or around the femoral bifurcation. 22/24 of PA (12 surgical; 4 endovascular stenting; 1 ultrasound guided thrombin injection; 4 ultrasound guided compression; 1 embolisation), 8/12 of TA (7 surgical; 1 endovascular stenting) and 3/3 MA (2 surgical; 1 combined surgical + endovascular stenting) required intervention. One patient underwent primary major amputation (popliteal TA) with a further three patients requiring major amputation post intervention (1 MA post bypass procedure, 1 PA post vessel ligation, 1 PA secondary to percutaneous intervention presenting with distal embolization requiring vessel ligation). Overall 30day mortality was 5.1% (n=2).


Introduction
An increase in life expectancy, intravenous drug abuse and the number of vascular surgical interventions all have led to a parallel increase in the incidence of infra-inguinal aneurysms. Infra inguinal aneurysms can be life and limb threatening due to their potential to cause embolism, thrombosis, and compression of surrounding structures and depending on aetiology, rupture. True infra-inguinal arterial aneurysms (TA) are most commonly seen in the popliteal arteries, whereas pseudoaneurysms (PA) are seen mostly in the femoral artery [1]. The majority of true popliteal aneurysms remain asymptomatic with reported complication rates of 8% to 39% over 3 -8 years follow up respectively [2,3]. Femoral pseudoaneurysms on the other hand are usually symptomatic with a reported complication rate of up to 47% [4]. Rupture is relatively uncommon for noninfected femoral PAs, with a reported incidence of 1 -12% [5,6], but is potentially catastrophic [7]. Femoral PAs may present with acute thrombosis associated with substantial risk of limb loss (up to 28%) if collateral circulation is poor [6]. Hence, timely diagnosis and management before complications ensue is paramount.
Not only do infra-inguinal aneurysms pose a threat to limb, there is also an association between femoral, popliteal and aortic aneurysms, with the incidence of aorto-iliac aneurysms in those with popliteal and femoral aneurysms up to 62% and 85% respectively [6,8].
We describe our experience with infra-inguinal aneurysms admitted to a tertiary vascular department covering a catchment area of 800,000 inhabitants. amputation with a further patient requiring ileo-femoral bypass for limb salvage. One infected PA following an interventional procedure for iliac occlusive disease, required vessel ligation of the common femoral artery and subsequent major amputation. Of the remaining 2 requiring surgical intervention, one underwent a direct suture repair whilst the other underwent vessel ligation. 8/12 TA required intervention (Table 3), with 7 undergoing surgical intervention and one endovascular stenting. Five underwent lower limb arterial bypass, 1 underwent attempt at lower limb bypass but was abandoned due to no suitable conduit and poor run off vessel whilst the popliteal TA presenting with acute ischaemia underwent transfemoral amputation. All 3 mycotic aneurysms required intervention, two lower limb arterial bypass reconstructions, one of which occluded resulting in a major lower limb amputation, whilst the third underwent endovascular stenting only to later require vessel ligation.
Of the 12 patients with symptomatic true aneurysms, 7 had concomitant incidental aneurysms, as shown in Table 4.

Mortality
30-day mortality was 5.1% (n=2), with one patient presenting with a painful popliteal true aneurysm and chest sepsis who was previously turned down for abdominal aortic aneurysm (AAA 78mm in diameter) repair, who was deemed too frail for intervention (either limb salvage or major amputation), whilst the second patient died of PAs accounted for 24/39 (median age 49 years, range 18-85), TAs 12/39 (median age 76 years, range 65-98) and MAs for 3/39 (median age 55 years, range 51-69), Table 1, Figure 1 depicts the management pathways and outcomes.

Presentation
The majority of our sample had a symptomatic presentation, 31/39. 23/24 of the PAs were symptomatic on admission, with the majority presenting with localized pain and swelling with or without a discharge from an overlying sinus. One PA was asymptomatic and identified on graft surveillance following infra-inguinal arterial reconstruction for occlusive disease. 5/12 of the TAs presented with localized pain and swelling (all 5 located at the popliteal artery), with 4/12 presenting with short distance intermittent claudication (3 popliteal TAs, 1 common femoral TA), 2 presenting with critical limb ischaemia (both popliteal TAs) and the final TA presenting with acute limb ischaemia (popliteal TA). Three of the aneurysms were classed as mycotic, with presentations of intermittent claudication, acute limb ischaemia and localized painful swelling, and all three were located at different sites (Table 2).

Etiology
Etiology of each type of aneurysm was studied and 10/24 PAs (41.7%) were the direct result of Intra Venous Drug Abuse (IVDA), all of which were infected, with only one other PA (post interventional procedure) presenting with localized sepsis. The remaining were secondary to percutaneous access for interventional procedures (7/24, 29.2% -5 post coronary intervention, 2 post interventional radiology), disruption of vascular anastamosis for lower limb arterial reconstruction (3/24, 12.5%), following orthopedic procedures (3/24, 12.5%) and following non iatrogenic trauma (1/24, 4.2%). Table 2 displays the site of the aneurysms, with the common femoral artery being the predominant site.

Size
The median size of the aneurysm sac was 30mm (range 10-93). Whilst the median diameter of the TAs was 41.5 mm (range 20-62). True aneurysm of the CFA measured 32mm and all other popliteal TA with a mean of 40.6mm and a median of 43mm. The median sac diameter was 41mm (range 38-50) in mycotic aneurysms. Table 3 with 12 requiring open surgical intervention. All 10 PAs due to IVDA required vessel ligation, 1 of which culminated in major lower limb   sepsis in the peri-operative period following ligation of an infected femoral PA.

Discussion
Infra inguinal aneurysms constitute over 90% of non-aortic aneurysms [9]. In recent years, the increases in catheterization procedures and vascular surgical interventions have been important factors in the higher prevalence of pseudoaneurysms. Patients may present with either symptoms of extremity ischaemia secondary to thrombosis and embolism or symptoms related to infection or compression of neighboring veins and nerves. Aetiology plays a vital role both in presentation and management of infra-inguinal aneurysms. PAs in intravenous drug abusers almost always present with infection needing ligation of the affected blood vessel(s). All 10 patients with infected PAs in our study required vessel ligation, whilst infection is uncommon in iatrogenic PAs allowing primary repair. True aneurysms, on the other hand, usually present with either acute or acute on chronic ischaemia and rarely rupture.
In our study more than 90% of TAs involved the popliteal arteries, a finding consistent with the literature [10], while more than 90% of PAs involved femoral (common femoral, superficial femoral and profunda femoris) arteries with only two cases involving popliteal and crural arteries.
Popliteal true aneurysms impact more on limb viability than femoral true aneurysms, mainly because of thrombotic/embolic events. Many studies advocate surgery in asymptomatic popliteal aneurysms to prevent future complications [2,11,12]. However, a policy of operating on all asymptomatic infra-inguinal aneurysms is unjustified and potentially dangerous; many of which are asymptomatic and remain so over several years Trickett et al. [13], performed lower limb duplex ultrasonagraphy on 1074 males attending screening or surveillance for abdominal aortic aneurysms. Only 1% of those screened had a popliteal aneurysm, none of which developed a complication (in the five year follow up) related to their asymptomatic popliteal aneurysm [13]. Selective surgical treatment, based on symptoms, the amount of mural thrombus, the diameter of the aneurysm and the life expectancy of the patient, is likely to produce better results [14]. Other studies have suggested surgical treatment should be provided to all patients with symptomatic popliteal artery aneurysms and asymptomatic aneurysms of more than 2 cm [14]. It should be remembered that the risk of amputation for symptomatic popliteal aneurysms is high (20-69%) [1,9] and that the life expectancy of these patients may be short due to high incidence of comorbid conditions [14]. This is in contrast to asymptomatic true popliteal aneurysms with an incidence of amputation about 4% [9]. In the present study all the popliteal aneurysms were symptomatic and 8 underwent some form of intervention, two were treated conservatively first already had a common femoral-posterior tibial reverse vein bypass graft for a SFA aneurysm and symptoms were managed conservatively as symptoms were deemed due to distal bypass anastamosis. Second patient had a long standing symptomatic presentation and electively surgically explored but procedure abandoned due to absence of native long saphenous veins.
The remaining two patients were deemed not physiologically fit for intervention or limb salvage, and as such were treated palliatively. Of those patients with TAs, 8.3% ultimately required major limb amputation on the same admission. True aneurysms have historically been treated surgically with either exclusion of the aneurysm and subsequent arterial bypass or resection of the aneurysmal segment with an interposition bypass. Open surgical repair with general or regional anaesthesia ay poses a high risk for these patients and as such endoluminal stent grafting has become an alternative to surgical treatment [9,[22][23][24].
With regards to PAs, etiology and presence or absence of infection helps in deciding treatment options. As PAs in IVDAs are almost always infected, ligation of the involved artery has been the treatment of choice. In our study all the infected PAs (10/10 in IVDUs and 1/13 Iatrogenic PA) required ligation of involved arteries, with only one PA requiring vessel ligation secondary to IVDA undergoing an arterial bypass for limb salvage. Ultrasound Guided Compression   [15], is a safe and cost-effective method for achieving pseudoaneurysm thrombosis in the noninfected, non-neurovascular/sin compromised, post iatrogenic injury (ie arterial puncture) [16]. However, USGC has limitations, including a long procedure time and discomfort to patient. It is less likely to be successful in large PAs (larger than 3cm), those with chronic PAs (as they have become endothelialised), those with large diameter neck and those who can't tolerate the associated discomfort [17]. Its success rates can vary, depending on the experience of the practitioner, and have been reported as high as 75% and above [18]. One third of Iatrogenic PAs (4/12) were successfully treated with USGC in our study whilst another one third were successfully treated by covered stent graft. Durability and long-term outcomes of stent grafts are still awaited [19,20]. A recent Cochrane review concluded that Ultrasound Guided Thrombin Injection (USGTI) might be considered as the new 'gold standard' for the treatment of non-infected post percutaneous intervention pseudoaneurysms [21]. In our study one patient was successfully treated by USGTI whist another was treated with coil embolization.
The incidence of amputation for pseudoaneurysms varies depending on the aetiology and treatment required. The incidence of major lower limb amputation following ligation of infected femoral artery pseudoaneurysms ranges from 11% to 33% [25]. In our study the overall amputation of PAs was 8.3%, with a major lower limb amputation rate of 18.2% (n=2/11) for those patients with an infected PA. Of those patients with an infected PA requiring vessel ligation, only one subsequently underwent arterial reconstruction with autologous vein (reversed long saphenous ilio-femoral bypass, resulting in limb salvage) once the sepsis was adequately controlled. A further patient in this group underwent trans femoral amputation following vessel ligation due to the acute nature of the ischaemia and ongoing sepsis, with amputation being a lifesaving procedure. The majority of studies reporting on infected PAs secondary to IVDA document small patient numbers. Padberg et al. [26], in a study of 18 patients with infected femoral false aneurysms secondary to IVDA, reported on their aggressive use of limb revascularisation due to their concerns about high rates of limb loss when limiting their initial management to vessel ligation and debridement. Twelve of the 18 patients underwent revascularisation in the initial peri-operative period, resulting in 3 amputations and 13 secondary arterial operations in this re-vascularised group, in contrast to no amputations in those patients undergoing vessel ligation with no reconstruction [26]. Both Padberg and Arora et al. [27], advocate a test clamp of the distal external iliac/proximal common femoral and assessing pedal doppler signals. Should a pedal Doppler signal be present upon test clamping they suggest no further need for immediate arterial reconstruction. In contrast to Padberg et al., a study of 16 patients by Patel et al., reported on their use of aggressive revascularisation in such patients, with 15/16 patients undergoing immediate revascularisation upon vessel ligation and debridement, with only one late graft failure, whilst the remaining 14 patients had functional limbs with no claudication or rest pain [28]. Klonaris et al., documented their experience of utilising the internal iliac artery as a patch or conduit for arterial reconstruction in nine patients with infected false aneurysms secondary to IVDA [29], with the internal iliac artery being utilized as a patch in five patients and an interposition graft in four patients. None of these nine patients suffered perioperative complications nor had signs of infection or required limb amputation over a median of 19 months follow up [29]. A review of treatment options in these patients reported that even immediate revascularisation procedures through non infected tissues, following ligation resulted in early and late graft infection rates of 21% and 32% respectively, with early and late amputation rates of 10% and 11% respectively, with a risk of anastomotic dehiscence of 14% [30]. Even delayed revascularisation resulted in significant morbidity, with long term graft infection and amputation rates of 6% [30].
30-day mortality rate of infra inguinal aneurysms in this study is 5.2% (n=2), which is well below the reported mortality in the literature. The published mortality for infra inguinal aneurysms varies depending on the type and site of aneurysm, with 30-day mortality for all popliteal aneurysms ranging up to 14% [31,32] and 30-day mortality for all femoral pseudoaneuryms quoted at 4% [33].

Conclusion
Our results compared favorably to the few national observational studies. Due to the risk of rupture, extremity ischemia and amputation, infrainguinal aneurysms result in considerable morbidity and mortality. To achieve high success rates in symptomatic and asymptomatic patients we suggest early diagnosis and appropriate treatment.