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Transaortic Renal Artery Endarterectomy for Renal Artery Atherosclerosis
Renal revascularization is indicated for renin-mediated hypertension and for progressive renal insufficiency secondary to renal artery arteriosclerosis. Renal artery atherosclerotic lesions account for 90% of all renal artery stenoses and are most often a manifestation of generalized atherosclerosis. Operative options in carefully selected patients include percutaneous angioplasty with or without a stent, a bypass, or an endarterectomy. Endarterectomy is the most technically challenging. Three specific patterns of atherosclerotic disease are relevant to renal endarterectomy procedures.
The most common atherosclerotic renal artery stenosis results from a spillover of aortic plaque. This type accounts for 65% of the stenoses and is bilateral in 75% of patients. An additional 30% of atherosclerotic renal artery stenoses manifest as focal eccentric or concentric narrowings limited to the proximal 1.5 cm of the artery. These stenoses are usually unilateral. These first two types of atherosclerosis are easily treated by endarterectomy.
Atherosclerotic renal artery stenoses have been reported to be progressive, causing approximately an additional 20% reduction in the vessel's cross-sectional area per year. Nearly 10% of all lesions initially causing a greater than 60% reduction of the cross-sectional area eventually progress to occlusion. These facts must be considered in the decision to perform a bilateral endarterectomy in a patient whose severe disease affects one renal artery with only modest disease affecting the contralateral artery.
Renal artery endarterectomy was one of the earliest forms of renal revascularization, first reported more than 40 years ago. Renal artery occlusive lesions secondary to atherosclerosis are amenable to four principal means of endarterectomy: aortorenal endarterectomy through an axial aortotomy, aortorenal endarterectomy through the transected infrarenal aorta, direct renal artery endarterectomy in situ, and eversion renal artery endarterectomy, with subsequent reimplantation of the artery. The specific intervention undertaken depends upon the extent of aortic and renal artery disease, as well as the necessity to perform a simultaneous aortic reconstructive procedure.
Operative Technique
Exposure
The usual approach to the renal arteries is an anterior one through the base of the mesocolon and root of the mesentery for all endarterectomy types, except for a unilateral direct renal artery endarterectomy, in which case an extraperitoneal approach after medial visceral rotation is favored. The patient is placed supine on the operating table, and a rolled blanket is placed transversely under the lower back so as to accentuate the lumbar lordosis. A supraumbilical transverse abdominal incision is preferred; it is extended from the contralateral anterior axillary line to the ipsilateral posterior axillary line. The small bowel is displaced from the abdominal cavity in a bowel bag, and the transverse colon is retracted into the upper abdomen with the aid of a fixed retractor. The ligament of Treitz is divided and the duodenum is then mobilized, being retracted to the right. The retroperitoneum over the aorta is incised, and dissection is advanced cephalad to the level of the left renal vein. The left renal vein is mobilized by ligating and transecting its contributory adrenal, gonadal, and lumbar veins.
In the case of transaortic endarterectomy, the renal arteries are skeletonized from their aortic origin to a point well beyond the obvious distal extent of atherosclerotic plaque. Small nonparenchymal branches, such as those to the adrenal gland, must be transected and ligated close to the renal artery. This extensive mobilization is time consuming but is needed to facilitate easy eversion of the renal artery during the endarterectomy.
The aorta is dissected about its circumference to above the superior mesenteric artery. This requires incising dense surrounding neural and fibrous tissues and dividing the periaortic diaphragmatic crus. The crus is transected perpendicular to its fibers and the aorta with the electrocautery. Ligation and transection of lumbar arteries may also be necessary to free the aorta completely from surrounding tissue, although these vessels are usually temporarily occluded with microvascular clamps.
Exposure of the renal artery for a direct unilateral endarterectomy is best provided with an extraperitoneal approach similar to the conventional medial visceral rotation used for an aortorenal bypass. Patient positioning and the surgical incisions are the same as for other revascularizations. The renal arteries are approached by medial reflection of the colon and foregut structures to the contralateral side. The renal vein is dissected from the vena cava to the renal pelvis; it is extensively mobilized by transecting its small contributory venous branches. The renal artery is then dissected from its aortic origin to a point well beyond the obvious atherosclerotic plaque, which is usually just beyond the first branching of the main renal artery.
Systematic anticoagulation is achieved with intravenous administration of heparin 150 U/kg before clamping the aorta and renal artery. Mannitol (12.5 g in an average adult) is administered intravenously at the same time to establish a diuresis. The four forms of endarterectomy are performed differently.
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