Many surgeons prefer a midline transperitoneal incision, as shown in Figures 111.1 to 111.4. Position the patient supine. Prepare and drape the abdomen from the nipples to the knees to allow a midline incision with the possibility of extending the bypass to the femoral arteries in the groin if necessary. Place a sterile towel over the genitalia and an iodophor-impregnated plastic adhesive drape over all exposed skin to protect the prosthetic graft from skin flora. Make a midline incision from the xiphoid to the midhypogastrium or symphysis pubis (Fig. 111.1A). Cover the transverse colon and omentum with a moist lap and elevate superiorly out of the abdominal cavity. Sharply mobilize the third and fourth portion of the duodenum to the right and off the infrarenal aorta by dividing the ligament of Treitz (Fig. 111.1B). Pack the small bowel in a moist towel and retract to the right. Pack and retract the descending and sigmoid colon laterally and inferiorly if necessary. The aneurysm should now be well exposed. Self-retaining retractors such as the Omni are very helpful. An alternative retroperitoneal approach is presented in Figures 111.5 and 111.6.

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 staying slightly to the right of the midline (Fig. 111.2A). More than 90% of abdominal aortic aneurysms are infrarenal. The superior neck of the aneurysm (area of normal aorta just proximal to where the aneurysmal widening begins) then lies just distal to the renal arteries and posterior to where the renal vein crosses over the aorta. Exercise care to avoid injury to these vessels in dissecting the neck of the aneurysm for clamping. The left renal vein may be dissected circumferentially and retracted proximally with a vein retractor. Dividing the left gonadal vein, lumbar vein and adrenal vein branches will allow further retraction of the left renal vein for better visualization of the juxtarenal aorta. Rather than risk tearing the left renal vein during an unusually difficult exposure, it may be intentionally divided at the onset and oversewn adjacent to the vena cava while preserving the above branches. On reviewing films prior to surgery, look for the retroaortic left renal vein anatomic variant as it is highly susceptible to accidental injury during clamping and subsequent massive, difficult-to-control hemorrhage.

The ureters lie close to the aneurysm and are most susceptible to dissection or retraction injury where they cross anterior to the iliac bifurcation to enter the pelvis. The common iliac veins adhere closely to the arteries and should be carefully separated from them only for a distance that is sufficient to allow clamping of the arteries (Fig. 111.2B).

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 100-U/kg heparin intravenously. Clamp all vessels gently to avoid dislodging atheroma or thrombus
as emboli. Open the anterior wall of the aneurysm longitudinally staying to the right of the origin of the inferior mesenteric artery. Remove mural thrombus and suture-ligate bleeding lumbar arteries. 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. 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.