Direct Surgical Repair of Juxtarenal and Suprarenal Aneurysms of the Abdominal Aorta




Historical Background


The surgical management of abdominal aortic aneurysms was first pursued by direct aortic ligation as reported by Matas in 1923. Likewise, beginning in 1906, Halsted and Reid at the Johns Hopkins Hospital attempted to treat suprarenal aortic aneurysms in five patients by the placement of partially occlusive metal bands. Subsequent strategies included the induction of partial or complete thrombosis of aortic aneuryms by translumbar placement of intraluminal wires to increase wall thickness and reduce the risk of rupture. In 1949 Nissen wrapped Albert Einstein’s aortic aneurysm with cellophane, borrowing upon a technique described by Rea. Einstein eventually succumbed to rupture 6 years later. Complete resection of an abdominal aortic aneurysm and graft replacement was reported in 1951 by Dubost and colleagues, but this technique was often complicated by major bleeding from adherent nearby major venous structures. The modern technique of endoaneurysmorrhaphy with intraluminal graft placement was popularized by Creech in the 1960s and is the current approach for most aortic aneurysms, including juxtarenal abdominal aortic aneurysms (jAAAs) and suprarenal abdominal aortic aneurysms (sAAAs). The application of a left retroperitoneal approach to address extensive aneurysms of the abdominal aorta is credited to Williams.




Indications


The surgical repair of asymptomatic jAAAs and sAAAs carries a greater incidence of postoperative complications than the surgical repair of infrarenal aortic aneurysms. As a consequence, a 6-cm diameter is considered the threshold for repair of asymptomatic aneurysms. A slightly lower threshold (5.5 cm) may be considered for women, given a presumed increased risk for rupture. Symptomatic jAAAs and sAAAs should be repaired urgently.




Preoperative Preparation





  • Beta-blocker should be initiated before surgery with a target heart rate of less than 70 beats per minute.



  • Aspirin and statin therapy may reduce perioperative cardiovascular risk and should be maintained throughout the recovery period.



  • Thienopyridines should be halted 7 to 10 days before surgery because of risk of excessive bleeding, but should be resumed in the postoperative period if used as part of a dual antiplatelet regimen for patients who have received a drug-eluting coronary stent.



  • Double lumen endotracheal intubation is not necessary for left lung isolation for jAAA and sAAA repairs.



  • Intraoperative arterial line monitoring of blood pressure is recommended.



  • Intravenous access with large bore central lines should be established for rapid infusion, and pulmonary artery catheterization is mandatory for patients with cardiac dysfunction.



  • Intraoperative autotransfusion devices are preferred to return collected red blood cells from the aneurysmal sac and bleeding lumbar vessels.



  • Systemic normothermia should be maintained.



  • Perioperative prophylactic antibiotics should be given for 24 hours with intraoperative redosing for every 1500 mL blood loss.





Pitfalls and Danger Points





  • Intraoperative hemorrhage from a proximal anastomosis constructed to inhospitable aortic tissue or an iatrogenic venous injury to an unrecognized retroaortic left renal vein



  • Precipitous hemodynamic changes during aortic clamping and reperfusion leading to myocardial injury and renal dysfunction



  • Visceral ischemia from embolization during dissection and clamping of the proximal aorta or due to unrecognized stenosis of the visceral vessels



  • Colonic ischemia from interruption of the inferior mesenteric artery or collateral blood supply from the pelvis





Operative Strategy


Retroperitoneal or Transperitoneal Exposure


For a jAAA, a retroperitoneal or transperitoneal approach may be used. Randomized trials have not demonstrated major differences in outcomes for either approach. In general, a transperitoneal approach affords rapid access to the abdomen and ease of bilateral iliac exposure when large iliac aneurysms are present, but upper abdominal organs limits access to the visceral segment of the abdominal aorta. The left renal vein may be divided to facilitate suprarenal aortic clamping during a transperitoneal approach, but left renal dysfunction may ensue. The left retroperitoneal approach facilitates exposure of the upper abdominal aorta for cross clamping at or above the superior mesenteric artery or celiac axis—a strong advantage in a sAAA—but limits access to the right iliac artery and may require intraluminal right iliac control ( Box 24-1 ).



Box 24-1





  • “Hostile” abdomen secondary to multiple prior transperitoneal operations or presence of a stoma



  • Inflammatory aortic aneurysm



  • Horseshoe kidney



  • Need for suprarenal endarterectomy



RELATIVE INDICATIONS FOR RETROPERITONEAL EXPOSURE


Selection of Site for Proximal AORTIC Control


Preoperative computed tomography (CT) imaging is mandatory to determine the level of proximal aortic control. Features that suggest an appropriate clamp site include lack of significant calcification or mural thrombus, along with a normal aortic diameter. A jAAA implies the aneurysm extends to the lowest renal artery, necessitating aortic clamping above the renal arteries so that an anastomosis can be performed across the lower border of the renal arteries. In practice, a clamp may be placed across the jAAA neck if not overly burdened by atheroma, mural thrombus, or calcification to allow the surgeon to open the jAAA, evacuate the blood and mural thrombus, control lumbar vessels, with subsequent placement of the clamp above the renal arteries when performing the anastomosis. If feasible, such a strategy significantly reduces the period of renal ischemia.


For a sAAA, the aneurysm extends to involve varying portions of the renal artery origins and/or the visceral vessels. The segment of aorta between the celiac and the superior mesenteric artery may be more normal in caliber, but the presence of orificial disease near the superior mesenteric artery may preclude clamping in this area. If this visceral segment of the abdominal aorta is heavily diseased, the proximal clamp should be applied above the celiac axis to avoid embolization of debris into the visceral vessels. The supraceliac segment of aorta is also more easily exposed that the region between the superior mesenteric artery and celiac axis.




Operative Technique


Control of the Suprarenal Aorta


The suprarenal aorta can be approached from either a transperitoneal or retroperitoneal exposure. In the transperitoneal exposure, the duodenum is mobilized to the right with the root of the mesentery. The retroperitoneal tissues along the lower border of the pancreas are opened, and the inferior mesenteric vein should be divided from its confluence onto the splenic vein to allow a static retraction device to reflect the pancreas cephalad. The left renal vein is appreciated coursing across the aorta and overlying the renal artery origins. By sacrificing the lumbar and gonadal branches to the left renal vein seen just left of the aorta, the left renal vein can be retracted to expose the suprarenal aorta for clamp application.


Control of the Supraceliac Aorta


In the retroperitoneal exposure of the jAAA or sAAA, the left-sided abdominal structures are reflected medially. The left retroperitoneal space is developed cephalad, and the spleen is displaced medially until the left crural fibers of the diaphragm are appreciated. The suprarenal aorta is covered by the left crural diaphragmatic muscle and a layer of thick fascia, which is continuous with the pleura. Both layers can be divided with electrocautery after a clamp or index finger is insinuated beneath these layers to develop a surgical plane along the left side of the aorta. Short, direct arteriolar perforators to the crus are rarely encountered during this maneuver, but if encountered, direct suture repair of the aortic wall with pledgeted 4-0 polypropylene sutures placed in horizontal-mattress fashion may be required. Sharp dissection is used to dissect the retroperitoneal tissues from the region surrounding the origins of the visceral vessel to allow secure clamping, and reduce bleeding as well as embolization during proximal aortic clamping. The anterior and posterior tissues just above the celiac axis are easily mobilized to allow proximal aortic control.


Retroperitoneal Exposure


Incision for a Juxtarenal Abdominal Aortic Aneurysm


The tenth interspace is selected as the site of incision for most patients with a jAAA ( Fig. 24-1 ). The incision is carried posteriorly along the superior border of the eleventh rib for 4 to 6 inches. In some patients, a limited incision in the diaphragm is required to separate the tenth and eleventh ribs, but this may be repaired primarily during closure and a left pleural tube is not required. The retroperitoneal plane is entered at the tip of the eleventh rib ( Fig. 24-2 ) and the peritoneal sac bluntly swept from the undersurface of the anterior abdominal wall. The anterior abdominal incision should be kept parallel to the course of the rib to avoid crossing the intercostals nerve bundles as they merge onto the abdominal wall, thus reducing the risk of denervating the flank muscle with resultant muscle bulging. The anterior portion of the incision is carried forward to the lateral border of the rectus, which may curve caudally to the umbilicus or below, in the case of iliac artery involvement.




Figure 24-1


Patient positioning and incision for a retroperitoneal approach to the abdominal aorta. The patient is turned on the right side with the shoulders nearly vertical and the hips rotated as horizontal as possible. The operative table is flexed with the patient’s flank positioned on the table break. A kidney rest fixed to the table may also be used to further elevate and flatten the region of the torso between the lower costal margin and iliac crest. The left flank and both groins may be prepped into the field, but right groin exposure may be limited. The patient position is stabilized by the use of a bean bag. Although the depicted incision courses onto the tip of the twelfth rib, it can and should be varied to the interspace above depending on the proximal extent of the aortic aneurysm and the patient’s body habitus. For example, an incision in the tenth interspace, over the eleventh rib, is required for optimal exposure of most juxtarenal aortic aneurysms.



Figure 24-2


Developing the appropriate retroperitoneal plane in performing a left-sided medial visceral rotation. Typically the left kidney is elevated out of its bed, but there are circumstances (e.g., retroaortic left renal vein) in which the plane is developed anterior to the kidney, which is left in situ.


Incision for a Suprarenal Abdominal Aortic Aneurysm


The ninth or tenth interspace is the choice of incision for most patients with a sAAA (see Fig. 24-1 ). The incision is carried posterior along the rib for 4 to 6 inches. The ninth and tenth ribs are fused on the costal margin anteriorly, and the bridge of cartilage must be divided with electrocautery or bone-cutting scissors after dissection of the anterior abdominal muscular attachments. Typically, the superior epigastric artery must be ligated under the divided costal margin. With the costal margin divided, the retroperitoneum and diaphragm are evident. The diaphragm is opened for 4 to 6 inches to facilitate blunt retroperitoneal mobilization of the left-sided abdominal viscera. The peritoneal sac is bluntly mobilized from the under surface of the anterior abdominal wall muscles. The incision is carried anteriorly and parallel to the course of the tenth rib and then curves downward, lateral to the left rectus muscle, beyond the level of the umbilicus.


Repair of a Juxtarenal Aortic Aneurysm with Iliac Artery Involvement


Incision


With the patient in a supine position, a midline incision is made from the xiphoid to the pubis. The peritoneum is entered, and after inspection of the abdominal contents, the transverse mesocolon is reflected onto the lower chest and wrapped with a warm towel to prevent desiccation. The small bowel is kept intracavitary and packed to the right abdomen with a wet towel, whereas the duodenum is mobilized at the root of the mesentery from the retroperitoneum as it lies on the jAAA. A static retraction device is fixed to the table. Wide retraction blades are placed against the small bowel and mesocolon, and shallow blades are placed to steady the left abdominal wall and the bilateral lower quadrants.


Exposure of the Abdominal Aorta


The fibrofatty retroperitoneal tissue is opened in the midline to expose the jAAA. With electrocautery dissection, the retroperitoneum is mobilized from the anterior aorta and the inferior mesenteric artery is identified and dissected. If the inferior mesenteric artery is patent, it may need to be reimplantated into the aortic graft depending upon the adequacy of colonic perfusion. The tissues overlying the common iliac arteries are opened and suitable sites selected for distal control.


Exposure of the Iliac Arteries


For patients with aneurysmal involvement of both common iliac arteries, individual control of iliac bifurcation vessels facilitates construction of the distal anastomosis. The dissection plane should adhere to the vessel wall during exposure of the iliac artery bifurcation to reduce the risk of ureteral injury. The exposure of the internal iliac vessels may be obscured by the presence of a large common iliac artery aneurysm, and intraluminal control of the internal iliac after opening the aneurysm may be the only option for control. If the internal iliac artery can be visualized, it should be mobilized along its lateral walls, but not circumferentially, to avoid iatrogenic iliac vein injury. Once the iliac bifurcations are dissected free of the surrounding structures, lower quadrant shallow retraction devices are replaced with deeper retractors to “hook and hold” the ureters and colonic structures lateral to the region for distal anastomosis.


Division of the Renal Vein


In the transperitoneal approach for a jAAA, mobilization of the renal vein is key to securing a suitable suprarenal cross-clamp. If the neck of the aneurysm is tortuous, consideration should be given to early division of the left renal vein, with preservation of the left gonadal and adrenal veins for left renal drainage. In many patients, simple downward traction on the aneurysm may straighten the neck and facilitate dissection of the left renal vein with gentle blunt dissection. If such a maneuver appears to facilitate visualization of the suprarenal neck, then renal vein division is likely not needed. Ligation of the left lumbar and gonadal veins on the lower edge of the left renal vein will allow its cephalad mobilization. Once mobilized, a narrow and deep static retraction blade is placed under the left renal vein. The vein is retracted cephalad to expose the suprarenal aorta to the origin of the superior mesenteric artery.


Proximal and Distal Control


Before clamp application, the patient should be anticoagulated with intravenous heparin (100 IU/kg). The right renal artery and superior mesenteric artery may occasionally originate so close to each other to render clamping below the superior mesenteric artery yet above both renal arteries impossible. If the aortic neck intervening between the right and the often lower left renal artery is normal, a cross-clamp can be applied at that site for proximal control, with only left renal ischemia induced by clamping. If the aorta in the pararenal region is not hospitable for secure control, supraceliac control of the aorta should be obtained ( Box 24-2 ). Although backbleeding will occur from the celiac artery and the superior mesenteric artery, this can be controlled with a compliant intraluminal endovascular aortic balloon inserted coaxially through the surgical graft.


Mar 13, 2019 | Posted by in VASCULAR SURGERY | Comments Off on Direct Surgical Repair of Juxtarenal and Suprarenal Aneurysms of the Abdominal Aorta
Premium Wordpress Themes by UFO Themes