Preemptive treatment of type II endoleak for abdominal aortic aneurysm with renal fusion (horseshoe kidney)

Introduction

Endoleaks can occur in to up to 30% of patients following endovascular aneurysm repair (EVAR), of which type II endoleaks are the most common, comprising over 75% of all endoleaks. ¹ Multiple patent lumbar arteries (LAs), the inferior mesenteric artery (IMA), and multiple (accessory) renal arteries are common sources of type II endoleaks. The risk of endoleak rises with increased number and size of patent arteries feeding the abdominal aortic aneurysm (AAA) sac.^2,3 Preemptive coil embolization of periaortic arteries addresses this increased risk. Consent for publication was obtained from the patient and long-term follow-up reported here.

Case presentation

A 69-year-old man was referred with an asymptomatic 5.5 cm infrarenal AAA complicated by renal fusion. The choice between open or endovascular repair was influenced by anatomic considerations related to managing the renal fusion and adhesions from a previous sigmoidectomy for diverticulitis. Mild, stage 2 chronic kidney disease with creatinine of 1.1 mg/dl and eGFR 66 mL/s was not considered a contraindication to either option. While an open repair was not contraindicated, computed tomographic angiography (CTA) demonstrated anatomy reasonable for an endovascular approach which was strongly preferred by the patient. A pair of large lumbar arteries originated from a single 8 mm orifice at L3. A patent inferior mesenteric artery measured 2 mm. An accessory renal artery to the isthmus of the fused renal mass measured 2 mm in diameter (Figure 1). Right and left main renal arteries appeared to supply the remainder of the renal parenchyma.OPEN IN VIEWER

One week prior to EVAR, the L3 LA was selectively cannulated and embolized. Arterial access was established and the aortogram demonstrated optimal visualization of the L3 LA at 21° right anterior oblique projection. The L3 lumbar artery was cannulated using a 5 French catheter (Figure 2). Three 0.018-inch 3 mm by 8 cm hydrogel-coated detachable coils (Terumo, Somerset, NJ) were deployed using a 2.8/3.0 French 130 cm coaxial catheter system (Progreat®, Terumo, Somerset, NJ, USA). The following week, percutaneous EVAR was performed with a stent graft: 28 × 111 mm main body, 20 × 56 mm right iliac limb, and 24 × 90 mm left iliac limb (Zenith®, Cook, Bloomington, IN, USA). Completion aortography demonstrated no endoleak, with preservation of both right and left renal arteries, and both hypogastric arteries. The patient had an uneventful recovery.OPEN IN VIEWER

Initial surveillance with CTA and duplex ultrasound demonstrated absence of contrast in the renal isthmus with focal parenchymal atrophy (Figure 3). Both the isthmal accessory renal and inferior mesenteric arteries had thrombosed.OPEN IN VIEWER

Five years after the repair, CTA demonstrated no endoleak, and AAA sac diameter had decreased from 5.5 to 5.0 cm. Renal function remained satisfactory with stage 3a chronic kidney disease: creatinine 1.5 mg/dl and eGFR 55 mL/s.

Discussion

Type II endoleak has a reported rupture rate of 0.5% to 0.9%.^4,5 However, its clinical significance remains controversial. While some studies showed no survival difference with or without secondary intervention, a 2022 analysis of the Japanese national experience with EVAR demonstrated significant correlation between persistent type II endoleak and late adverse events, including sac enlargement, reintervention, rupture, and mortality. ⁵

Although type II endoleaks are often found at time of repair, the majority of these endoleaks resolve without intervention. However, over 25% of patients may require a secondary intervention, and 18% will have persistent endoleaks requiring continued surveillance. ¹ Delayed onset of type II endoleak has been linked with aneurysm sac expansion. ¹ Current Society of Vascular Surgery AAA guidelines recommend treatment of type II endoleaks if the aneurysm sac continues to expand following EVAR. Continued surveillance at 6-month intervals for the first 2 years postoperatively is recommended for those without sac expansion. ⁶

Preemptive embolization of periaortic vessels, specifically LAs and IMA, may be considered in patients at high risk for type II endoleaks after EVAR. Development of type II endoleak has been associated with 3 or more patent LAs and patent IMA greater than 3 mm in size.^2,3 Marchiori et al found LA size of greater than 2 mm was a positive predictive factor for persistent type II endoleak beyond 6 months post repair. ⁷ Based upon these data, the 8 mm LA, the patent IMA, and the isthmal renal artery would place this patient at increased risk of type II endoleak.

Embolization of periaortic collateral arteries or the aneurysm sac has been performed safely with good outcomes.^8,9 Neurological complications following LA embolization are not well documented, but there is a theoretical risk of spinal cord ischemia. The most common approach to coil embolization of periaortic vessels is a percutaneous transarterial approach via femoral or brachial artery; after EVAR, the aneurysm sac becomes less accessible. Translumbar and transcaval approaches appear to be safe alternative options with good efficacy. Less common alternatives are laparoscopic and open surgery. ⁴

Renal fusion complicates EVAR as there are usually multiple renal arteries. The presence of accessory renal arteries not only increases risk of endoleak but also may induce renal injury if they are involved in the repair. A systematic review published in 2022 consisting of 50 patients with concomitant AAA and renal fusion who underwent EVAR found that the mean number of renal arteries was 3.5. The risk of functional renal compromise post exclusion of an accessory renal artery appears to be minimal. ¹⁰ This patient had a single accessory renal artery with a relatively small size of 2 mm on preoperative CTA. Extrapolating from previous data on LAs, there was low likelihood of endoleak from this vessel and likely equally low risk of causing renal compromise. Preoperative planning for EVAR in the setting of renal fusion requires consideration of two important factors. First is the size, number, and parenchymal distribution of the renal arterial supply. Second is the patient’s baseline renal function and whether the loss of accessory renal arteries may adversely affect the postoperative renal function. Accordingly, recognition of a particularly dominant accessory renal artery may shift the operative recommendation to open AAA repair for purposes of reimplantation.

Conclusion

In patients who are at risk for developing postoperative type II endoleaks, preoperative coil embolization may be a safe and effective strategy to reduce its incidence, promote sac shrinkage, and lower reintervention rates post EVAR. A reasonable criterion for consideration of preoperative coil embolization is an artery perfusing the aneurysm sac with diameter greater than or equal to 3 mm. In patients with concomitant horseshoe kidney, large accessory renal arteries may supply a significant portion of renal parenchyma, and preservation versus embolization of these arteries may be considered on a case-by-case basis.