K.E.M. Radiology

Figure 1: Fusiform dilatation of the Infra-renal Abdominal Aorta (Max transverse diameter - 5.58 cm).

An endovascular aortic repair was performed. Using a 5F left brachial arterial access, an infrarenal aortogram was performed. This showed fusiform dilatation of the abdominal aorta. Under general anesthesia, l femoral arteriotomies were performed on both sides. Over an AUS guide wire, an aortic stent graft was placed across the aneurysm. Stent grafts were placed across both common iliac arteries. A check angiogram showed good flow across the stent graft. However, on the late arterial phase, persistent filling in of the aneurysmal sac was observed. This was due to retrograde filling of the aneurysm from a collateral from the inferior mesenteric artery - suggestive of type II endoleak. Conservative management was advised with follow-up CT to be done after six months. 

A CT aortogram performed six months later, showed persistent endoleak into the aneurysmal sac with increase in maximum transverse diameter to 6.1 cm (earlier 5.58 cm) (Figure 2). In view of persistent endoleak and an increase in the size of the aneurysm, endovascular embolization of endoleak was decided with NBCA glue as the embolization agent.

Figure 2: CT aortogram performed six  months later showed increase in the transverse diameter of the abdominal aortic aneurysmal sac.

Figure 3: CT aortogram also revealed the filling in of the aneurysmal sac retrogradely via a collateral from the IMA confirming Type II endoleak. 

 Interventional technique:

After preprocedural assessment of the clinical and radiological findings, the patient was counselled on the treatment plan and informed consent was obtained. The procedure was performed under monitored anaesthesia care.

Using 6F right CFA access, a selective SMA angiogram was performed. This showed delayed filling of the aneurysmal sac via a collateral from the IMA (Video 1).

Video 1: Selective SMA angiogram performed using a 4Fr C1 catheter via a right CFA access shows delayed filling of the aneurysmal sac via a collateral from the IMA. 

A brachial access was chosen for this embolization procedure to provide a more direct and stable route for navigating the catheter into the SMA to reach distally till the collateral of IMA which caused retrograde filling of the aneurysm sac (Video 2).

Video 2: Superselective angiogram of SMA branch which shows filling in of the aneurysm sac via collateral from IMA. 

It was particularly important to reach as distally as possible close to the site of endoleak to assure complete embolisation of the endoleak and to avoid residual or recurrent endoleak. The microcatheter was advanced almost until the site of retrograde filling in of the aneurysmal sac and a check angiogram was performed to confirm the proximity to the sac (Video 3 and Figures. 4&5).

Video 3: Angiogram after passing the microcather distally near the site of retrograde filling in of the aneurysmal sac before performing embolization.

Figures 4 & 5: Selective catheterisation of the SMA via left brachial access with angiogram confirming the endoleak arising from a collateral from IMA.

Video 4: NBCA glue embolization of the endoleak was performed using 33% glue concentration to successfully exclude the aneurysm sac from circulation.

Video 5: Post embolization SMA angiogram showed no residual endoleak.

Video 6: Post embolization abdominal aortogram revealed normal  flow within the aortic stent graft, complete embolization of the feeding artery to the aneurysm sac and successful exclusion of the aneurysm sac, indicating no further endoleak.

Video 7, 8  AP and lateral projections): On follow up imaging performed 18 months later, there was successful embolization with no residual filling in of the aneurysmal sac.

Figure 6: Plain CT of the abdomen on 18 month follow-up showing reduction in the maximum transverse diameter of the infrarenal abdominal aortic aneurysm.

Discussion:

EVAR is an increasingly preferred choice for management of an abdominal aortic aneurysm (AAA) which is aimed to completely exclude the aneurysmal sac from the circulation. One of the most common complications of EVAR procedure is endoleak. An endoleak is defined as the continued filling of the aneurysm sac, which is not excluded from the systemic arterial circulation. Five types of endoleaks have been described in literature [1]:

Type I: Leak at graft ends, either proximal(A) or distal(B) or common iliac artery(C)

Type II: Aneurysmal sac filling via branch vessel (e.g. lumbar or inferior mesenteric artery)

Type III: Leak through a defect in graft fabric, either junctional separation of the modular components or fractures or holes involving the endograft

Type IV: Porous graft (intentional design of graft)

Type V: Endotension.

Type I and III endoleaks must be treated immediately to protect the patient from aneurysm rupture. 

Management of endoleaks:

Type II endoleak is the most common complication post-EVAR accounting for up to 44% of all endoleaks. Risk factors for the development of a type II endoleak include an increased number of patent aortic collateral arteries and increasing age. Type II endoleak may be classified by the time of onset into early, (diagnosed less than 30 days post-EVAR), late (diagnosed more than 30 days post-EVAR) and persistent (lasting more than 6 months). Current guidelines advice conservative approach for type II endoleak without sac expansion.

The most common technique of endoleak management is transcatheter embolization of branch vessels using coils, glue, or thrombin. Including the aneurysmal sac in embolization of the feeder artery gives better long term results, as the aneurysmal sac can take feeders from new collateral branches [2]. When a type II endoleak arises from the inferior mesenteric artery, superior mesenteric artery is the common route to access. When the endoleak is from a lumbar collateral, the iliolumbar artery to the lumbar artery, and then into the aneurysmal sac is the route of flow. Non-target embolization can rarely occur, resulting in neurological symptoms due to embolization of lumbar arteries. Another option for the treatment of type II endoleak is translumbar embolization which involves image guided percutaneous needle placement into the endoleak using fluoroscopic/ dynamic CT guidance. Although the translumbar approach may be useful for accessing posterolateral endoleaks, it can be difficult to access endoleaks anterior to the stent graft and to cannulate lumbar artery origins, which face away from the catheter. Transcaval embolization of type II endoleak has also been used. In this, the common wall of the vena cava and aorta is punctured, and the catheter  is advanced into the aneurysmal sac for glue embolization [3].

For types I and III, Tiny endoleaks can sometimes be left without further intervention because they may resolve spontaneously. Large leaks cannot be left untreated. They can be managed by simple balloon angioplasty, or by placing an aortic cuff at the site of leak, aiming to add extra radial strength and coverage to the endograft attachment site [4]. Glue embolization of the aneurysmal sac has been reported as a method of treating type 1 endoleaks in those patients without sufficient native aorta to accommodate an extension stent/cuff [5]. Type IV endoleaks are usually managed conservatively. Type V endoleak or endotension is defined as a continued high intra sac pressure following EVAR without evidence of continued aneurysm sac perfusion. Management of this type is controversial, and the use of extension cuffs, relining the original stent graft with another graft or open surgical conversion are treatment options.

Conclusion:

Endovascular management (EVAR) is an increasingly preferred method for management of abdominal aortic aneurysms (AAA). Successful complete exclusion of the aneurysm from the circulation is crucial. Endoleak is the most common complication of EVAR procedure and is of 5 types. Understanding the imaging findings of various types of endoleaks is important to prevent sac enlargement and rupture. Type II endoleak can be managed conservatively, or treated in case of increasing size of the aneurysmal sac. Treatment of type II endoleak can be done using transarterial approach, percutaneous or transcaval approach, with the the aim to embolize the aneurysmal sac. Type I and III endoleaks need immediate management.

References:

1. Green N, Sidloff DA, Stather PW, Bown MJ, Sayers RD, Choke E. Endoleak after endovascular aneurysm repair: current status. Reviews in Vascular Medicine. 2014 Jun 1;2(2):43-7.

2. Shimohira M, Hashizume T, Suzuki Y, Kurosaka K, Muto M, Kitase M, Mizutani M, Shibamoto Y. Triaxial system for embolization of type II endoleak after endovascular aneurysm repair. Journal of Endovascular Therapy. 2013 Apr;20(2):200-4.

3. Scali ST, Vlada A, Chang CK, Beck AW. Transcaval embolization as an alternative technique for the treatment of type II endoleak after endovascular aortic aneurysm repair. Journal of vascular surgery. 2013 Mar 1;57(3):869-74.

4. Fox LA, Powell A. Troubleshooting techniques for abdominal aortic aneurysm endograft placement: When things go wrong. Techniques in vascular and interventional radiology. 2001 Dec 1;4(4):213-21.

5. Rusius VC, Davies RS, Hopkins JD, Duddy MJ, Smith SR. Successful glue embolization of a late type 1A endoleak causing abdominal aortic aneurysm rupture. Vascular and endovascular surgery. 2011 Feb;45(2):198-201.