Anatomy

In the current era of endovascular therapy, open repair tends to be reserved for patients who cannot undergo EVAR. Despite the advances in device design, there remain a number of anatomic constraints that mandate open repair (Fig. 131-1).²⁵ The proximal aortic neck is crucial to obtaining an endovascular seal and achieving technical success with EVAR; accordingly, no aortic neck or a hostile aortic neck is the leading indication for open repair.¹⁸ Proximal aortic necks that are short, angled, trapezoidal, have a high burden of thrombus, or are heavily calcified can compromise seal. In multiple studies hostile neck anatomy has been associated with graft-related complications, type I endoleaks, and early reintervention.^26–28 These patients are often better served with open repairs.

Anatomic constraints in the distal aorta and iliac arteries can also be preferentially treated with open aneurysm repair. A narrowed or calcified aortic bifurcation has been associated with limb thrombosis and EVAR failure.²⁹ Likewise, iliac artery occlusive disease, especially chronic total occlusion, can mandate open repair for reasons pertaining to both access and treatment. Concomitant common or external iliac artery aneurysms are also indications for open repair, especially in situations in which internal iliac artery patency needs to be preserved, such as in claudicants and patients at risk for colonic, pelvic, and spinal cord ischemia.³⁰ None of these cases is an absolute indication for open repair, especially with the introduction of newer devices such as branched endografts for the iliac arteries. However, open repair may offer the best long-term solution.

EVAR Conversion

Failure of a previous endograft due to migration or recalcitrant endoleak that is unable to be resolved via endovascular means requires open aneurysm repair. This can present at any time following EVAR. A recent meta-analysis demonstrated an average early conversion rate of 1.5% with an associated 12.4% mortality among 12,236 pooled patients, and a 1.9% late conversion rate with an associated 10% mortality among 14,289 patients.³¹ Despite this, single-institution case series from high volume referral centers have demonstrated superb results,^32,33 with mortality rates as low as 0% among 21 patients requiring explantation.³² These interventions can be quite complex and frequently require suprarenal and supraceliac aortic control. Furthermore, the aorta and surrounding tissue can often be severely inflamed, making it quite difficult to dissect the appropriate planes. Procedural conduct of the operation is critical and understanding how to manage the endograft (full/partial removal) is important. Full discussion of aortic endograft explant is beyond the scope of this chapter. Ultimately, endograft explant is probably best reserved for centers that perform high volumes of open repair and have significant experience with explantation.

Infection

Infection of either the native aorta or of a previous open or endovascular repair requires an open operation for definitive therapy. Endovascular salvage has been described, but this would be considered more of a palliative alternative or temporary bridge to open repair.^34,35 In cases of an infected prior aortic graft, excision of all prosthetic material and extra-anatomic reconstruction has long been the gold standard, but recent data suggest that the use of an aortic homograft³⁶ or rifampin-soaked Dacron may be equally efficacious in treating the infection.^37–39 However, we have found that only mycotic native aneurysms are well-treated primarily with in situ reconstructions; when treating infected aortic grafts with in situ reconstruction, reinfection has been an issue. In either situation debridement of as much infected tissue as possible is ideal in order to obtain source control. As stated earlier, EVAR or other endovascular techniques can be used but only for treatment in patients who are too high risk to undergo an open procedure; in other patients, these techniques are mainly considered temporizing measures.

Additional Circumstances

A number of special circumstances can also influence the decision to proceed with open aneurysm repair. The presence of a horseshoe kidney with multiple renal and isthmus arteries originating from the aorta and iliac arteries⁴⁰ is best served with open repair so that these vessels will not be excluded.⁴¹ Likewise, patients in which the patency of the inferior mesenteric artery (IMA) needs to be maintained, such as those with bilateral hypogastric artery occlusion, SMA stenosis/occlusion, or previous colectomy, may require open aneurysm repair as well. As a counterpoint, patient factors such as a history of previous laparotomy or retroperitoneal exposure, abdominal stomas, abdominal wall defects, or poor pulmonary function, might argue for a creative endovascular approach when the patient would otherwise be best treated with an open repair.

Selecting the Approach

Because the goal of any approach is to obtain adequate exposure of the affected aortic segment, both transabdominal and retroperitoneal approaches will be technically equivalent in many situations. Under these circumstances, selection of approach should be determined by surgeon preference and familiarity.

Some situations, however, would recommend one technique over another. The transperitoneal approach offers rapid access to the infrarenal aorta with little need for complex patient positioning and is ideal for use in emergencies. In addition, for surgeons unfamiliar with the retroperitoneal approach, the transperitoneal offers a more comfortable approach to the aorta. Access to the entire peritoneal cavity also allows the surgeon to address nonvascular intra-abdominal pathology. As compared with the retroperitoneal approach, it also offers better, but not exclusive, access to the right renal artery and the right internal and external iliac arteries, as well as the femoral arteries. It is, however, more difficult to expose the visceral aortic segment from this approach.

The retroperitoneal approach, usually via a left tenth interspace incision, allows for superior exposure of the visceral and supraceliac aorta as well as the left renal artery. This is useful in managing patients with pararenal aortic aneurysms and type IV thoracoabdominal aortic aneurysms. Additionally, in patients who have undergone previous abdominal operations, it avoids the risk of “redo laparotomy” and eliminates the difficulties posed by intra-abdominal adhesions. It may also offer advantages in obese patients by allowing the abdominal contents to fall away from the surgical field.^69,70 Although exposure of the right internal and external iliac artery can be more difficult from this approach, it can still be performed with appropriate careful dissection. A single-institution retrospective study of 160 open aneurysm repairs published in 2007 demonstrated that with the advent of EVAR, the rates of transperitoneal aneurysm repairs significantly declined whereas retroperitoneal repairs significantly increased, likely because of the need for more proximal aortic repairs.⁷¹ In this report, the transperitoneal approach was associated with a greater blood loss and longer suprarenal clamp times.

A number of both retrospective cohort and randomized trials have compared the outcomes of patients undergoing aneurysm repair using transperitoneal and retroperitoneal approaches. Depending on the study, retroperitoneal repair has been associated with significantly decreased postoperative fluid requirements, pulmonary edema, pneumonia, respiratory failure, postoperative ileus, shorter length of intensive care unit and overall hospital stays, shorter time to full recovery, and less costs.^70,72,73 Other studies have disputed this, showing equivalency between the two procedures regarding these variables.^69,74 Data regarding hernias have been mixed, with studies showing that the retroperitoneal approach is associated with more,⁷⁴ equal,⁷⁰ or fewer hernias and bulges.⁷³

Exposure

The patient is positioned supine on the operating table with the arms abducted, and the abdomen is prepped and draped from the nipples to the knees. A midline incision is made from the xyphoid to the pubis; if necessary, the xyphoid can be excised and the incision carried to the inferior boarder of the sternum. This allows for maximal exposure. The abdominal contents are examined for any pathology that might alter the planned procedure. The omentum and transverse colon are retracted cephalad, and the small bowel is packed in the right hemiabdomen. Adequately protected with either warm moist towels or a sterile plastic covering, both structures can be eviscerated out of the abdominal cavity to gain more working space if needed. A self-retaining retractor, such as the Bookwalter (Codman and Shurtleff, Inc., Raynham, Mass) or Omni (Omni-Tract, St. Paul, Minn) retractor, greatly facilitates exposure and should be set up at this point.

To expose the aorta, the ligament of Treitz is divided, the third and fourth portions of the duodenum are reflected to the patient’s right, and the periaortic lymphatic and connective tissue is ligated and divided (Fig. 131-5). Care must be taken to avoid injury to the inferior mesenteric vein; this structure can, however, be divided to facilitate exposure. The incision in the posterior peritoneum is then continued caudally in this plane to expose the entire infrarenal aorta. Although starting to the left of the aorta at the ligament of Treitz, the incision in the posterior peritoneum should course to the right of the aortic midline to prevent injury to the inferior mesenteric artery, sigmoid mesentery, and autonomic nervous plexus at the bifurcation. In cases in which a tube graft will be used and the distal anastomosis will be to the aorta itself, the dissection does not need to proceed beyond what is necessary to obtain distal control at the level of the bilateral proximal common iliac arteries.

Once the appropriate aortic segments are exposed, the proximal and distal clamp sites are identified. Encircling the vessels with silastic vessel loops or cloth umbilical tape is not necessary and increases the risk of injury to posterior structures, especially the iliac veins. Only enough exposure to apply a clamp is needed. Care must be taken to avoid injuring or avulsing closely related venous structures. The patient is systemically heparinized, and the aorta and iliac arteries are clamped. Distal clamps are usually applied first to prevent any thrombus from embolizing to the legs during application of the proximal clamp. The aneurysm is opened via a longitudinal aortotomy, which transitions to a T-shaped incision at the proximal and distal ends to allow for the graft anastomosis (Fig. 131-9). The proximal anastomotic site is cleared of thrombus and calcium, and an end-to-end anastomosis is performed using a running polypropylene suture. A discussion of more complex proximal anastomoses for suprarenal and type IV thoracoabdominal aortic aneurysms can be found later in the section on retroperitoneal repair. The use of aortic retention sutures or a self-retaining retractor placed in the aneurysm sac helps to facilitate exposure. Thrombus is then cleared from the remainder of the aneurysm sac and back-bleeding lumbar vessels are controlled; management of the inferior mesenteric artery is discussed in its own section later in this chapter. The distal reconstruction is performed in a similar fashion (Fig. 131-10) allowing for forward flushing of the graft and back bleeding of the distal vessel before completing the anastomosis.

After hemostasis has been obtained, the aneurysm sac is closed over the graft using a running absorbable suture. The posterior peritoneum is likewise closed (Fig. 131-11). Both of these maneuvers help to exclude the bowel from the retroperitoneal and prevent contact between the bowel and the graft. If the sac or retroperitoneum is unable to be approximated over the graft, the omentum can be brought down to cover the graft. It is critical to obtain separation of the graft from the bowels to prevent future aortoenteric fistulization. The intestines are then returned to their normal anatomic position, and the anterior abdominal wall closed according to surgeon preference.

The incision starts in the 10th intercostal space at the posterior axillary line; this can be varied depending on the proximal extent of the aneurysm (Fig. 131-12). It is carried onto the abdomen, where it runs lateral and parallel to the lateral boarder of the left rectus muscle and terminates below the umbilicus at a level determined by the distal extent of the intended arterial reconstruction. The skin and subcutaneous tissues are divided to expose the anterior fascia of the external oblique. The external oblique, internal oblique, and transversus abdominis muscles are sequentially opened over a short distance using a combination of blunt dissection and electrocautery. Care must be taken not to violate the peritoneum. The peritoneum is then blindly freed from the abdominal wall and diaphragm using careful blunt digital dissection. This permits the abdominal cavity to be opened to the level of the diaphragm. Exposure can be increased by entering the chest through the 10th intercostal space contiguous with the abdominal portion of the incision by dividing 2 to 3 centimeters of the diaphragm. The left psoas muscle is identified, and the peritoneal and retroperitoneal contents are swept anteriomedially throughout the length of the wound, as well as off the inferior surface of the diaphragm. This exposes the entire intra-abdominal aorta (Fig 131-13A). At this stage, the left ureter should be identified and protected, because it runs anterior to the aorta and left common iliac artery. By staying on a plane directly anterior to the iliac arteries, the right ureter can also be identified and protected. A Bookwalter or Omni retractor can now be put in place to assist with exposure. If the patient has a posterior left renal vein, it may be advisable to not mobilize the kidney during the aortic exposure and to leave it in place in the retroperitoneum. Alternatively, it can be divided for exposure as long as the gonadal branch is preserved.

Arterial Reconstruction

The use of a retroperitoneal incision is ideal for reconstruction of suprarenal and type IV thoracoabdominal aortic aneurysms given the exposure it provides. After heparinization and supraceliac cross-clamping, the aneurysm is opened with a longitudinal aortotomy up to the level of normal proximal aorta, whereupon the aortotomy is transitioned into a T-shaped incision; it is important to have previously identified the origin of the left renal artery and to have divided the renal lumbar veins to avoid injuring these structures during this maneuver (Fig. 131-13B). The left renal artery is freed from the aortic wall with a small cuff of surrounding aorta and retracted out of the immediate field.

Once the proximal extent of the aneurysm has been opened, the celiac, SMA, and right renal arteries are identified from the inside the aorta. Any significant stenosis detected on preoperative CTA, or at the time of operation, can be treated with either endarterectomy or a balloon-mounted stent deployed through the open aorta.⁷⁸ The proximal extent of the graft is beveled to incorporate the celiac, SMA, and right renal arteries, and the proximal anastomosis is completed using a running polypropylene suture (Fig. 131-13C). The proximal graft is clamped, and the supraceliac cross-clamp is removed to allow perfusion of the viscera and right kidney (Fig. 131-13D). The left kidney is now revascularized by bypass with a sidearm from the graft. If a bypass is to be performed, a hybrid stent graft can be fashioned as a sidearm from the main graft before aortic cross-clamping in order to reduce left renal ischemia time and to facilitate the anastomosis (Fig. 131-14). Once the anastomosis to the left renal artery is complete, the aortic cross-clamp can be shifted distally on the graft to allow for complete renal perfusion (Fig. 131-13E). Minimizing ischemic time to this area is paramount; thus proper conduct of the operation and attention to technique is critical.

Note should be made on the preoperative CTA as to the patency of the IMA. If it is thrombosed, then it is of no further consideration. On the contrary, if there is significant SMA disease, bilateral hypogastric artery occlusions, a large IMA, or prior colectomy, IMA preservation may be indicated. However, IMA management should not be guided by imaging alone. At the time of operation, brisk back-bleeding from the IMA suggests that it can be safely ligated, whereas sluggish or no back-bleeding from an IMA that is known to be patent, or evidence of colonic ischemia, argues for revascularization. This can be accomplished either by reimplantation of the IMA into the graft using a small cuff of surrounding aorta or in an end-to-end fashion from a sidearm attached to the body of the graft. This is easily performed from both the transperitoneal and retroperitoneal approaches.

The presence of renal anomalies, such as a horseshoe kidney, pancake kidney, and crossed-fused renal ectopia, complicates open aneurysm repair. Such abnormalities are most frequently associated with aberrant or multiple renal arties.^79–84 Furthermore, accessory renal arteries originating from the iliac arteries or aneurysm sac are not uncommon.⁸³ Almost all of these findings are evident on preoperative CTA; thus they should not come as a surprise at the time of operation. Many of these arteries are small and only detectable on fine-cut CTA. Thus renal abnormalities should alert one to the need for a fine cut CTA rather than standard CT. Their identification also may merit additional investigation to interrogate the anatomy of the collecting system and ureters in order to detect any associated abnormality or aberrancy; this frequently involves the use of urography.^79,81,84 A renal perfusion scan can also be of assistance in this setting in helping to determine the functionality and contribution of not only each kidney but each portion of the respective kidneys. This is then helpful to determine what, if any, tissue can be sacrificed. Management is difficult because these situations pose technical challenges with respect to both exposure and revascularization, and longer aortic cross-clamp times have been reported.⁸² It is generally recommended that all important accessory renal arties be reimplanted; this can be done with branch grafts or through use of a Coselli’s patch. Both transperitoneal^81,84 and retroperitoneal^80,82,83 approaches offer options with regard to exposure, vascular control, and reimplantation. If multiple critical arteries need to be reimplanted, necessitating longer ischemic times, the use of extracorporeal perfusion strategies may be helpful to minimize kidney injury.

Venous Abnormalities

Based on surgical and radiological studies, significant venous abnormalities of the renal veins and IVC are present in between 1% and 10% of the population respectively.^85–88 The most common abnormalities include retroaortic left renal vein, circumaortic left renal vein, left-sided IVC, and duplicated IVC; accessory left renal veins and preaortic confluence of the iliac veins have also been described. These abnormalities can pose significant challenges with regard to aortic exposure and can complicate the operation.^88–90

With a circumaortic or retroaortic left renal vein, the posterior component can be disrupted when obtaining control of the aorta during a transperitoneal approach. In cases of a retroperitoneal approach, altering the exposure to leave the kidney in the renal fossa can assist in exposing the aorta. It is important to note that a retroaortic left renal vein can enter the vena cava either in an orthotopic position or at the more caudal L4 to L5 spinal level with the gonadal and ascending lumbar veins. Ultimately, dividing the left renal vein is acceptable as long as the gonadal and other collateral vessels are preserved.

CT scan is effective at diagnosing these abnormalities and determining their exact anatomic location. Failure to appreciate them on preoperative imaging can result in catastrophic hemorrhage,^90–92 and formulating a strategy to managing these abnormalities before the operation is important. Even when a CT has been obtained, great diligence is warranted; the absence of expected normal venous anatomy should alter the surgeon to the possibility of aberrant venous anatomy.

Coexisting Pathology

When an aneurysm and other pathology are concomitantly diagnosed, the one that is more life threatening should be addressed first. Additional studies may be necessary to fully define the extent of the nonaortic pathology because the results may impact the decision to proceed with aneurysm repair. Although it has been successfully described in limited series,^93,94 simultaneous operations, especially those that include the gastrointestinal tract, are to be avoided in order to prevent infection of the prosthetic graft. An exception can be made for clean procedures, such as renal resection.^95,96 However, the overall clinical status of the patient has to be taken into account. A better approach may be closely staging the procedures,⁹⁷ because an increased incidence of aneurysm rupture has been reported following unrelated laparotomy.^98–101 The ability to do this has been greatly advanced by the advent of minimally invasive surgical techniques for gastrointestinal and genitourinary tract pathology, limiting recovery following these procedures and allowing the aneurysm repair to proceed without significant delay. Alternatively, the best approach may be treating the aneurysm with an endovascular aneurysm repair in order to facilitate a more rapid recovery and to prevent violation of the peritoneum or retroperitoneum.¹⁰² In the rare instance that coexisting pathology is found intraoperatively, the aneurysm repair should proceed as planned unless the secondary pathology is so severe as to directly impact the patient’s immediate life expectancy or poses significant risk of graft infection.

A special mention should be made of cholelithiasis. Gallstones are more prevalent in patients with abdominal aortic aneurysms.¹⁰³ Despite this, the rate of acute cholecystitis in the early postoperative period is low.^104–106 Simultaneous open aneurysm repair and cholecystectomy have been reported using either a transperitoneal approach or a combination of retroperitoneal abdominal aortic aneurysm repair and laparoscopic cholecystectomy.^106–109 Although simultaneous aneurysm repair and cholecystectomy have been shown to be safe, it is generally not necessary and not worth the risk of graft infection.¹⁰⁵ In the rare case of postoperative acute cholecystitis, a percutaneous cholecystostomy tube can be used to temporize the situation until the patient has recovered from the aneurysm repair.

The application and removal of an aortic cross-clamp results in a complex series of physiologic derangements governed primarily by the level at which the aorta is clamped.^110,111