Plate 153

Aneurysms of the abdominal aorta occurring below the renal vessels should, in general, be replaced. This is particularly true if they are enlarging and producing pain or if there is evidence of impending or actual rupture. In poor-risk patients with small aneurysms less than 5 cm in diameter, observation may be the better course. Many aneurysms are corrected by endovascular techniques, but an open operative approach is acceptable and sometime necessary alternative. Although the operation is of considerable magnitude, anticipated mortality associated with spontaneous rupture and exsanguination from an aneurysm is such as to warrant the risk of surgery in the great majority of patients. Emergency operations may offer the only chance of a patient's survival if there is evidence of leakage or rupture of the aneurysm. A past history of coronary artery disease is not a contraindication to surgery.

CT scan best defines the size and contour of these aneurysms. Transabdominal ultrasound is a good screening tool, but CT best defines size and proximal and distal extent. Aortography is carried out if there is a question about the extent of the aneurysm, if distal occlusive disease is present, and when renal vascular disease or mesenteric insufficiency is suspected. A thorough cardiac evaluation with an electrocardiogram, echocardiogram, and imaging stress test is performed.

In elective resection of an aneurysm, the preoperative preparation consists of emptying the large intestine by administering a mild cathartic. A fluid load of “crystalloid” is given at approximately 100 to 150 mL per hour beginning the evening before operation. Intravenous antibiotic coverage is started on call to the operating room. A nasogastric tube is inserted, and constant bladder drainage is initiated to follow accurately the hourly output of urine, especially during the immediate postoperative period. Catheters are placed for central venous and arterial monitoring, while a Swan-Ganz catheter may be useful in complex cardiac cases.

General anesthesia with endotracheal intubation is routine. The arterial line permits instantaneous evaluation of blood pressure changes, and blood gas sampling can be done when required. Several large-bore (16-gauge) catheters should be placed intravenously for adequate control of fluid and blood replacement.

The patient is placed in a slight head-down position to aid in natural retraction of the small intestine from the region of the lower abdomen. Intravenous catheters are secured in place in both arms and adequately protected from dislodgement. The urethral catheter is connected to a constant bladder drainage bottle. Since the presence of pulsations of the dorsalis pedis must be verified after the prosthesis has been inserted, some type of low support should be provided over the feet and lower third of the legs to assist in evaluating the presence of arterial pulsations.

A long midline incision is made from xiphoid to pubis (Figure 1). Many surgeons use a large open ring retractor for exposure. This retractor is secured to the side rail of the operating table and allows for the placement of multiple individual curved or angled adjustable retractors.

After rapid palpation and visualization of the aorta and confirmation of the diagnosis of aneurysm, steps are taken to empty the abdominal cavity of small intestine. Unless the abdominal wall is quite thick, the greater portion of the small intestine can be retracted upward and to the right and inserted into a plastic bag, the mouth of which can be partly constricted by a tape (Figure 2). Saline is added to the plastic bag to keep the intestine moist. A sterile gauze pad is inserted into the neck of the plastic bag to avoid undue constriction and prevent the escape of the small intestine from the bag. It may be advisable (if the aneurysm is sizable and involves the right common iliac) to mobilize the appendix, terminal ileum, and cecum and to retract the right colon upward. The small and large bowels are retracted laterally and superiorly using multiple adjustable retractors. Additional exposure can be gained by dividing the peritoneum about the ligament of Treitz to permit further retraction of the small intestine upward and to the right (Figure 2). What at first may appear to be an inoperable aneurysm eventually may prove to be rather easily resectable, since the aneurysm tends to bulge anteriorly and seems to extend up so high as to suggest involvement of the renal vessels (Figure 3). The bulk of the aneurysm tends to come forward from under the left renal vein. The incised peritoneum over the anterior surface of the aneurysm is reflected by blunt and sharp dissection until the left renal vein is visualized. Blunt and sharp dissection frees the left renal vein from the underlying aorta (Figure 4). The left renal vein is retracted upward with a retractor (Figure 5) to gain additional space for the application of the occluding clamp to the aorta above the aneurysm. The left renal vein can be divided, if necessary, to gain the final exposure. It does not need to be reanastomosed if the adrenal and gonadal vessel veins are intact.

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