Open Transperitoneal Surgical Treatment of Nonruptured Infrarenal Aortic Aneurysms

Exposure

The patient is placed in a supine position and prepared and draped from the nipples to the knees. A generous midline incision is made extending from the xiphoid process to the symphysis pubis. The abdominal contents are examined to rule out any undetected intra-abdominal pathology. If a concomitant pathology is found, although this is uncommon now, the overall guidelines are to treat the most life-threatening process first and avoid simultaneous operations. Typically, this means to proceed with AAA repair unless the unexpected findings carry increased risk for graft infection, such as an abscess or metastatic disease.

Following the abdominal exploration, the greater omentum and transverse colon are lifted superiorly and the small bowel is mobilized to the right side of the abdomen to expose the retroperitoneum. The retroperitoneum is then incised starting at the aortic bifurcation and moving superiorly, to the right of the inferior mesenteric vein, toward the ligament of Treitz to provide adequate exposure of the aortic neck region. The left renal vein can be visualized at this stage, and its absence should alert the surgeon to the possibility of a retroaortic position. The torrential hemorrhage from inadvertent injury of the anomalous left renal vein can be avoided by careful retraction and more careful placement of the aortic clamp ( Figure 1 ).

Infrarenal AAAs treated in current times with open repair often have challenging necks. Owing to extensive thrombus or limited length of the aortic neck, both renal arteries may need to be identified and controlled before the infrarenal clamp is placed. In such cases, the left renal vein may need to be mobilized by division of its tributaries. If division of the left renal vein is found to be necessary in challenging cases, its gonadal and adrenal tributaries should be preserved.

The distal extent of exposure depends on the condition of both iliac arteries. Usually, control of the common iliac arteries just beyond their origin is sufficient. However, control of the hypogastric and external iliac arteries may be needed in the presence of iliac aneurysms. Both ureters should be clearly identified at this stage. Circumferential control of the iliac vessels should be avoided to prevent iliac vein injury. The splanchnic nerve plexus, important to sexual function, crosses the proximal aspect of the left common iliac artery and is also prone to injury during dissection in this location. To maintain the exposure during the remainder of the procedure, a self-retaining retractor is used.

Clamping

Before cross clamping, systemic heparinization is initiated with a dose approximating 80 U/kg. Additional heparin may be given at later stages to maintain activated clotting time at 250 to 300 seconds. Distal control is achieved first, to decrease the risk of distal atheroembolism. This is followed by proximal aortic clamping. Owing to the complex physiologic and humeral responses to aortic occlusion, this step must be clearly communicated to the anesthesiology team. Aortic clamping increases the systemic arterial pressure secondary to increased systemic vascular resistance. Similarly, it results in redistribution of blood from organs distal to the aortic clamp toward the central venous circulation. Although these changes are less severe with infrarenal clamping than with more proximal clamp locations, they can affect myocardial demand and can result in decompensation in patients with significant coronary artery disease or ventricular dysfunction. This can be minimized by normalizing preload, afterload, coronary blood flow, and contractility.

Aneurysmorrhaphy

During aneurysmorrhaphy, the aneurysm sac is opened longitudinally, to the right of the IMA. The thrombus is evacuated, and the bleeding lumbar arteries are suture ligated from within the aneurysm. The IMA is similarly ligated in the same manner. The safety of IMA ligation depends on collateral circulation to the distal colon, which should be assessed on preoperative imaging as noted earlier. Intraoperative identification of a large meandering mesenteric or marginal artery indicates significant mesenteric occlusive disease and warrants IMA reimplantation or SMA revascularization. Otherwise, adequacy of the collateral colonic circulation is confirmed by assessing backbleeding of the IMA.

Dacron grafts are usually used for aortic reconstruction. The proximal anastomosis is performed in an end-to-end fashion using polypropylene suture. After ensuring hemostasis in the proximal anastomosis, the distal anastomosis is performed. In cases in which the common iliac arteries are dilated (≥2 cm), a bifurcated graft is used and the anastomoses are performed to the iliac artery bifurcation. In treating associated iliac aneurysms, sacrifice of both hypogastric arteries should be avoided. ( Figure 2 )