Aberrant Takeoff of a Right Accessory Renal Artery, Identified during an Aortoiliac Intervention

A 66-year-old man presented with lifestyle-limiting, severe bilateral buttock and thigh claudication (Fontaine class IIb). Only resting ankle-brachial indices (ABI) were obtained at presentation and were normal (0.93 right and 0.91 left). Diagnostic cine-angiographic images of the distal aorta with run-off using a 9-inch diameter image intensifier revealed diffuse atherosclerotic changes in the distal aorta, patent bilateral main renal arteries, and high-grade stenoses of both common iliac arteries with good distal outflow. A medium caliber artery originated immediately above the aortoiliac bifurcation, and was initially identified as a right lumbar artery.

A 20 mmHg, translesional systolic pull-back gradient across the right and left common iliac artery ostia was confirmed using a 4 Fr endhole catheter. The patient returned for an angioplasty and kissing stent placement of the aortoiliac bifurcation with balloon expandable stents deployed, sparing the ostium of the previously identified right lumbar artery. Post-procedural digital subtraction angiography (19-inch image intensifier) revealed an excellent angiographic result. The artery that was previously identified as a right lumbar artery was in reality an accessory renal artery, supplying the inferior pole of the right kidney.

Accessory renal arteries are found in approximately 15% of patients and may arise from a variety of locations, such as the distal infra-renal abdominal aorta, as in our case.¹ Early anatomic studies considered early main renal artery branching or small renal vessels arising from other vessels (inferior phrenic, adrenal, internal spermatic or ovarian artery) to be accessory renal arteries.² The currently accepted convention to define an accessory renal artery is used to indicate more than one renal artery, with each artery arising as a separate branch from the aorta or iliac artery.¹ Detection of these accessory arteries is of great importance when the accurate depiction of renal arterial anatomic structures is required, such as in cases of renal transplantation, surgical reconstruction of the abdominal aorta, renovascular hypertension, and as demonstrated by this report, in planning endovascular peripheral interventional procedures.³

Though most accessory renal artery dimensions are smaller than that of the main renal artery, the presence of the main renal artery with a diameter smaller than usual in a kidney with normal dimensions is indicative of the presence of an accessory renal artery.⁴ Use of a wide image intensifier to delineate the extent of the renal parenchyma perfused by the main renal arteries, based upon careful examination of the renal silhouette or contrast nephrogram and combined with attention to the caliber of the main renal and extra arteries, can be a tip-off to the presence of significant accessory renal arteries.

Percutaneous transluminal angioplasty of atherosclerotic iliac artery stenosis is an effective and established method of recanalization, with low complication rates and long-term results that approach those of surgical bypass procedures. Five-year patency rates approach 80–90%.⁵ This technical success rate has improved significantly, up to 95%, especially with the use of adjunctive stent placement.⁶ Almost exclusively, balloon-expandable stents are used at the aortic bifurcation. These stents have some favorable mechanical properties for application in ostial lesions and in the relatively straight common iliac arteries, where flexibility of the stent seems to be of relatively little importance. Balloon-expandable stents can resist the relatively high reconfiguration forces of fibrotic, calcified, or highly eccentric iliac stenoses. Furthermore, because the stent opens out with only minimal shortening, extremely exact placement in the aortoiliac orifice is ensured. It also provides easy access to jailed side branches. In this case, though complete occlusion of the accessory renal artery with a balloon expanding stent covering its ostium is not likely; it certainly could lead to plaque shift and distal embolization.

Though it is generally feasible to cross and angioplasty through balloon-expandable stent struts, it is important to emphasize that even transient reductions in renal blood flow can lead to ischemic injury, especially in the renovascular bed, given its very high oxygen requirements. Failure to recognize this variant during distal aorta and aortoiliac interventions could result in jailing and possibly occluding the renal artery, which could lead to ischemic renal injury. Using a wide (> 12-inch diameter) image intensifier and digital subtraction angiography could aid in recognition of this arterial variant.