Place the patient in a supine position, with a Foley catheter and appropriate monitoring devices in place. Prepare and drape the abdomen from the nipples to the knees. Cover the genitalia with a sterile towel. Secure all towels with iodophor-impregnated plastic adhesive drapes, rather than with sutures or towel clips. An antibiotic that is active against common gram-positive skin bacteria (e.g., a cephalosporin) is administered just before making the incision and for 24 hours postoperatively.

Most surgeons prefer a midline transperitoneal incision, as shown in Fig. 92.1, 92.2, 92.3 and 92.4. (An alternative retroperitoneal approach is presented in Fig. 92.5 and 92.6.) Extend the incision from the xiphoid to the midhypogastrium or below (Fig. 92.1A). Retract the transverse colon superiorly and divide the ligament of Treitz (suspensory muscle of the duodenum) to mobilize the duodenum to the right (Fig. 92.1B). Pack the small bowel into the right side of the abdominal cavity within a towel. Pack and retract the descending and sigmoid colon laterally and inferiorly if necessary. Self-retaining retractors such as the Omni are very helpful.

The midline incision has many anatomic advantages if a transperitoneal approach is used. In addition to providing maximal exposure of the peritoneal cavity, it affords a strong closure because several fascial and aponeurotic layers fuse as the linea alba. Retraction of the transverse colon superiorly displaces the transverse mesocolon superiorly, exposing the superior aspect of the root of the mesentery, which begins at the duodenojejunal flexure. Direct visualization and palpation of the ligament of Treitz (suspensory muscle of the duodenum) is then possible. This fibromuscular band arises from the right crus of the diaphragm and then passes posterior to the pancreas and splenic veins and anterior to the left renal vasculature. It may contain numerous small vessels. Reflection of the duodenum and small bowel to the right, and of the descending and sigmoid colon to the left, exposes the aneurysm, which is covered with parietal peritoneum.

Open the peritoneum over the aneurysm (Fig. 92.2A). Preserve as much of the hypogastric nerve plexus as possible because sexual dysfunction frequently results if these nerves are divided or devascularized.

In more than 90% of the cases, the superior neck of the aneurysm is below the origin of the renal arteries, where the left renal vein crosses the aorta. Exercise care to avoid injury to these vessels in dissecting the neck of the aneurysm for clamping. Rather than risk tearing the left renal vein during an unusually difficult exposure, it may be intentionally divided and ligated (preferably oversewn) to the right of the gonadal and adrenal branches to provide adequate, safe exposure with preservation of collateral drainage. The left renal vein may be retroaortic and thus highly susceptible to accidental injury and subsequent massive, difficult-to-control hemorrhage.

The ureters are also very near the aneurysm, and the potential for injury to these structures during dissection and retraction should be recognized. The ureters are most susceptible to
injury where they cross anterior to the iliac bifurcation to enter the pelvis. The common iliac veins are closely adherent to the arteries and should be carefully separated from them only for a distance that is sufficient to allow clamping of the arteries (Fig. 92.2B).

Aspirate blood from the inferior vena cava or aorta for preclotting of knitted Dacron grafts. (Preclotting of woven, “presealed” knitted, or PTFE grafts is unnecessary.) Then have the anesthesiologist administer heparin intravenously. Clamp all vessels gently to avoid dislodging atheroma or thrombus as emboli. Open the anterior wall of the aneurysm. At the superior and inferior necks of the aneurysm, extend the incision transversely in a T pattern through the anterior half of the wall. Leave the posterior portion intact for strong purchase of sutures. Remove mural thrombus and suture-ligate bleeding lumbar arteries. Retracting sutures or a self-retaining retractor placed in the wall of the aneurysm may be helpful. Remove any debris from both necks of the aneurysm.

If the inferior mesenteric artery is backbleeding, suture-ligate it from inside the aneurysm to avoid disturbing the collateral circulation to the distal inferior mesenteric artery. If there is concern regarding the viability of the colon at the conclusion of the procedure, reimplant the inferior mesenteric artery with a cuff of aortic wall into the graft. If the inferior mesenteric artery is not reimplanted, carefully inspect the bowel for signs of ischemia before closure of the abdomen.