Appropriate patient selection for endovascular intervention is paramount and dependent on therapeutic indication, anatomy, patient comorbidities, and acuity of the disease process. In the following text, we discuss considerations for patients with renal/mesenteric arterial occlusive disease, followed by considerations for patients with renal/mesenteric arterial aneurysmal disease.

For RAS, the indication for endovascular intervention is contingent on severity of stenosis, the presence and severity of presumed resulting hypertension, and extent of residual glomerular filtration capacity. For RAS, there is no accepted indication currently for “prophylactic” intervention. Endovascular intervention is considered only in patients with severe hypertension, who have failed medical management with at least three concurrent antihypertensive medications or have demonstrated progressive loss of renal function due to ischemic nephropathy in the setting of more than 60% RAS. The future role for endovascular intervention in treating RVH has been called into question by level I data demonstrating only modest reductions in blood pressure following renal artery stenting.¹⁷

Patients with critical stenosis or occlusion of at least two mesenteric arteries, in the setting of signs and symptoms consistent with CMI, are also potential candidates for endovascular management. Patients with atypical symptoms who may meet anatomic criteria for mesenteric occlusive disease often experience disappointing results following endovascular intervention.

Given the compromises inherent in management of AMI, often in the setting of uncertain bowel viability, hybrid open and endovascular approaches may represent the safest and most expeditious option. Particularly in regard to “acute-on-chronic” occlusion of the proximal SMA, with a patent distal segment preserved by collateral flow, surgical exposure at celiotomy enables distal SMA cannulation and sheath placement. Standard angiographic techniques are
then employed to cross the occlusive proximal lesion in a retrograde fashion, with subsequent angioplasty and stenting performed to restore pulsatile antegrade flow.¹⁸ We have employed this technique reliably under a variety of challenging clinical conditions with consistently good results.

In patients with disease in multiple mesenteric arterial segments and symptoms concerning for mesenteric ischemia, SMA revascularization, either via endovascular or open surgical approaches, represents the most reliable and effective method for resolving critical mid- and distal gut ischemia. Decompressive laparotomy should always be considered as an essential adjunct in these circumstances, regardless of revascularization method used, to facilitate selective resection of nonviable bowel if needed and limit the noxious effects of abdominal compartment syndrome in these already compromised patients.

In comparison, the safety and use of primary inferior mesenteric artery (IMA) endovascular intervention remains controversial in patients with disease in multiple mesenteric arteries. Recent series report relatively frequent procedure-related complications and poor outcomes following attempted IMA intervention.¹⁹ These results may in part be due to the progressive nature of occlusive vascular disease in the most distal aortic segment at the level of the IMA and resulting difficulty in resolving significant ostial stenoses with even high-pressure angioplasty techniques.

The criteria for elective repair of asymptomatic RAAs is controversial. Recommendations vary for intervention based on aneurysm diameter, also taking into account the size of the parent artery, extent of mural calcification, and rate of enlargement, if available. Consensus exists regarding treatment for all aneurysms larger than 3 cm in diameter.^20,21 Similarly, patients with intact but symptomatic true aneurysms, recent-onset false (pseudo-) aneurysms, and aneurysms resulting from associated FMD are also typically repaired promptly, given their presumed higher risk of rupture. RAAs in women of childbearing age with plans for future pregnancies are usually repaired, when recognized, at almost any size. Less agreement is present for RAAs larger than 2 cm but smaller than 3 cm in diameter, with treatment recommendations often customized based on individual circumstances.

There are no set size criteria for visceral artery aneurysm repair. Although larger aneurysms are thought to have an increased potential risk of rupture, small visceral artery aneurysms are also known to rupture and manifest with life-threatening hemorrhage. Therefore, most visceral aneurysms larger than 2 cm should be repaired when identified. This recommendation does not necessarily apply to poststenotic arterial dilations (not true aneurysms) and distal SMA aneurysms. The latter are generally best managed by embolization and/or resection of the dependent loops of adjacent small intestine. In most circumstances, ruptured visceral artery aneurysms are best managed by open or hybrid approaches, allowing for assessment of bowel or end-organ ischemia in conjunction with restoration of arterial flow.

Prior to attempted repair or exclusion, aneurysm location and access issues should be precisely determined via crosssectional imaging studies. Luminal plaque, thrombus burden, associated aneurysms, and preexisting dissections should also be noted. Finally, target vessel diameter should be determined at several intervals before, within, and after the lesion of interest to optimize coil, stent, and graft selection.

The preferred method of critical renal artery ostial lesion management is by balloon-expandable stent placement. In rare circumstance, angioplasty predilation may be required to advance the appropriate stent through the renal ostia and across the stenotic lesion. Renal artery stents range from 10 to 30 mm in length and 4 to 7 mm in diameter. Transfemoral approaches to the renal artery are generally preferred due to the shorter distance to target, smaller imaging fields, and abundant availability of purpose-specific instrumentation. However, cephalad angulation of the renal artery origins relative to the aorta, the presence of extensive infrarenal aortoiliofemoral arterial occlusive disease, or significant iliac artery tortuosity may favor consideration of the left brachial artery and descending thoracic aorta as the preferred route of access.

For the treatment of mid- to distal RAS in the setting of FMD, angioplasty alone is generally the preferred treatment modality. Either transfemoral or transbrachial approaches may be considered, depending on the considerations noted earlier. Care must be taken to minimize procedural trauma with precise determination of target artery diameter and selection of appropriately sized instruments (sheaths, balloons, and stents). Poor planning or ill-considered procedural technique may precipitate arterial dissection, thrombosis, and renal infarction.

Depending on the degree of lesional calcification, the extent of associated juxtaostial aortic occlusive disease, lesion length and associated target vessel tortuosity, balloon- or self-expanding stent grafts may be chosen for luminal reconstitution and may provide improved long-term patency in the proximal SMA.²² Cannulation of either the celiac or SMA may be achieved from both femoral and brachial approaches. However, in emergent or extenuating circumstances, left brachial access often proves more expeditious and effective. This is particularly true in the setting of high-grade ostial stenosis or occlusion, where brachial access and antegrade aortic sheath placement may provide improved guidewire, sheath, and crossing catheter pushability and trackability.

Successful wire cannulation of ostial SMA and celiac lesions may require “telescoping” techniques with different sheath and wire combinations (see in the following text). This is also true of attempts to deploy devices in the mid- and distal splenic artery, where a triaxial catheter and sheath combination extending into the target lesion is frequently most effective. Given the short and often tortuous nature of the celiac artery, stable sheath placement is challenging, often representing the most difficult aspect of the procedure.

Similar principles are used when treating aneurysms of renal and visceral arteries, including precise catheter positioning and stable sheath support. Aneurysm size, location, neck anatomy, and extent of tortuosity of feeding target vessels impact the strategy of repair. For example, for large retropancreatic splenic artery aneurysms, coil embolization of the aneurysm sac (preferably with large-end-first or nesting coils) prior to covered stent placement across the ostium of the aneurysm is necessary to ensure long-term procedural
success. For precise embolization of shallow or wide-necked aneurysms, adjuncts such as distal balloon occlusion with deployment of detachable coils may be necessary. For more accessible aneurysms with a wide-based aneurysm neck, bare metal stenting may be performed across the ostium of the aneurysm first, followed by placement of coils through the open interstices of the stent to keep the coils localized to the area of interest. Branch artery aneurysms usually occur at bifurcation points and are accompanied by small, welldefined necks and are ideally suited for embolization with microcoils (0.018-in catheter compatible) delivered through a triaxial delivery system.

The preferred size/shape of embolization devices or covered stents may be either accurately estimated from a preprocedural CT arteriogram or determined at the time of angiographic imaging and sheath placement. Based on these measurements, coil and plug diameters may be oversized by 20% of the target vessel diameter. The length of coils selected is derived from the anticipated arterial lumen surface area that requires embolization. Similarly, the length of vascular plugs selected depends on the target artery to be embolized and the estimated luminal flow. For example, higher flow arteries, such as those proximal to arteriovenous fistulae, usually need more extensive coverage to ensure definitive occlusion. Both self-expanding and balloon-expandable stent grafts are available. The former are also typically oversized by 20%, and the latter are usually sized 1 mm greater than the target artery diameter. Attention should be given to the sheath selection to ensure adequate diameter and length. The device-specific instructions for use (IFU) should be consulted in all circumstances prior to use of occlusion devices, or more generally, any endovascular device with the potential risk for significant vascular injury.