Open Surgical Treatment of Juxta- and Pararenal Aortic Aneurysms

Louis M. Messina

Background

An increased proportion of open abdominal aortic aneurysm (AAA) repairs are pararenal in location. This is because endovascular repair of infrarenal AAAs has achieved rapid acceptance since its introduction, and endovascular techniques may be applicable in up to 70% of cases. The major exclusion criterion for endovascular repair is lack of an adequate proximal implantation site, due to the origination of the aneurysm adjacent to or above the renal/visceral artery orifices.

Historically, repair of pararenal aortic aneurysms has been a challenge to the vascular surgeon. These aneurysms require more extensive exposure than infrarenal aortic aneurysms and can be more demanding technically. These demands include the requisite period of ischemia of the kidneys and viscera, the systemic pathophysiologic consequences of renal and visceral ischemia, greater blood loss, and a substantially higher increase in peripheral resistance due to the higher level of aortic cross-clamping. Whereas infrarenal aortic cross-clamping results in either no measurable or a small (10%) increase in peripheral resistance, a supraceliac aortic cross-clamp blocks 40% of the total cardiac output and results in a substantial increase in peripheral resistance.

Clinical outcomes for open repair of infrarenal AAAs have been well established. Pooled institutional data suggest a mean operative mortality rate of 3.5%. However, statewide data consistently show higher postoperative mortality rates after elective infrarenal AAA repair (e.g., in the state of Michigan, the rates are 7.5%, and in the state of California, they are 7.6%).

There have been relatively few comprehensive reports of the surgical outcome of pararenal aortic aneurysm repair. These reports consist largely of juxtarenal aneurysms and do not include suprarenal aneurysms that involve reconstruction on one or more renal arteries, pararenal aneurysms that require treatment of renal artery or visceral artery occlusive disease, or Type IV thoracoabdominal aneurysms. Of the published series of pararenal aortic aneurysm repair, the mortality rates vary from 0% to 15.4%. The incidence of postoperative renal insufficiency is approximately 25%, and the onset of permanent dialysis is approximately 7%.

Two central issues related to the surgical management of pararenal aortic aneurysms are the appropriate level of aortic clamping and the clinical and the intra-operative variables that correlate with the onset of renal failure or dialysis. There are two approaches to the level of aortic clamping during repair of pararenal aneurysms. Some groups favor routine supraceliac clamping, while others favor clamping at an aortic level no higher than necessary to accomplish aortic repair (selective aortic clamping). The advantages of routine supraceliac aortic clamping are the relatively short time required to expose the aorta at this level, reduced operative time, and less risk of untoward events during the more extensive dissection required to expose more distal segments of the pararenal aorta. However, routine supraceliac aortic cross-clamping involves a longer duration of liver and gut ischemia and a relatively higher increase in peripheral resistance and therefore cardiac stress.

We advocate clamping at an aortic level that is no higher than necessary to accomplish the repair. This minimizes liver/gut ischemia and the attendant systemic cytokine release and inflammatory response (with an increase in primary fibrinolysis) and reduces cardiac stress. In a recent study of the variables that correlated with the onset of postoperative renal insufficiency, there was a higher incidence with supraceliac aortic clamping than with selective aortic clamping. This higher incidence of renal complications occurred despite a shorter duration of aortic cross-clamping with supraceliac aortic clamping. The overall dialysis rate was 5.8%.

We analyzed 257 patients who underwent pararenal aortic aneurysm repair at UCSF in the largest published study of its kind. This included all aneurysm repairs requiring an aortic cross-clamp placed proximal to at least one main renal artery. There were three patterns of aneurysms treated:

Juxtrarenal aneurysms (n = 122), which required clamping above the renal arteries and sewing the graft just below the renal arteries
Suprarenal aneurysms, which required revascularization of at least one major renal artery (n = 58)
Juxtarenal or suprarenal aneurysms, which required repair of renal artery occlusive disease (n = 77)

In this study the mean aneurysm diameter was 6.7 cm (±2.1 cm). One third of the patients had abnormal renal function pre-operatively. Supraceliac aortic clamping was used in only 13% of these patients. In 87% of these patients, aortic cross-clamping was
done at a level no higher than necessary to complete a successful repair. The overall mean duration of renal ischemia was 31.6 minutes (±21.6 minutes). The overall postoperative mortality rate for these 257 patients was 5.8%.

Renal morbidity, defined conservatively as a postoperative increase in the creatinine of 0.5 mg/dl or greater, occurred in 41% of the patients; however, at the time of discharge, nearly 60% of these patients had normalized their creatinine levels. In another 20% of these patients, the creatinine was decreasing. The creatinine was unimproved in 20% of the patients at the time of discharge. Of the total patient group, 4.3% were on dialysis at the time of discharge.

In a regression analysis of factors correlated with renal morbidity, four dominant variables were identified: admission (basal) creatinine, duration of renal ischemia, the mean estimated blood loss, and the occurrence of gastrointestinal complications. Factors that did not correlate with renal morbidity were the aortic cross-clamp level and whether or not a renal artery revascularization was undertaken. Thus, these results indicate pararenal aortic repair can be performed with acceptable morbidity and mortality rates approaching those of infrarenal aortic aneurysm repair. There was an increased risk of impaired renal function postoperatively in patients with abnormal renal function pre-operatively, particularly when the duration of renal ischemia is prolonged. In the USCF series, the transient nature of the change in renal function in most patients suggested that the mechanism is acute tubular necrosis and not renal atheroembolization.

Surgical Approach

Incisions

There are three commonly used abdominal wall incisions to expose pararenal aortic aneurysms:

A long midline incision, xiphoid to the pubic ramus
A bilateral subcostal incision that extends from midaxillary line to midaxillary line and that can be extended superiorly along the midline to the xiphoid process
The flank/retroperitoneal approach

For complex reconstructions, the bilateral subcostal incision is favored. The advantage of this incision is the exposure of the aorta from the diagram to the iliac artery bifurcation. Most importantly, particularly in patients with deep abdominal cavities or who are obese, the surgeon’s hands work perpendicular to the aorta (Fig. 16-1). Finally, a flank retroperitoneal incision can be made particularly in patients who have had multiple previous abdominal operations.

Figure 16-1. Bilateral subcostal ilncision. This extends from midaxillary line to midaxillary line. Midline extension can facilitate further proximal exposure.

Pararenal Aortic Exposure

Two approaches can be used to expose the pararenal aorta, the transperitoneal infracolic or medial visceral rotation. For the transperitoneal infracolic approach, the distal iliac and infrarenal aortic exposure is obtained by incising the retroperitoneum and soft tissues over these structures, being careful to mobilize these tissues from left to right to avoid injury to the sympathetic and parasympathetic nerves. There are four key elements of the exposure of the pararenal aorta (Table 16-1).

The first key is to use a self-retaining retractor such as the vascular Omnitract (Minneapolis, MN). The second key is complete mobilization of the left renal vein. This includes transection and ligation of the gonadal vein, the adrenal vein, and the ascending lumbar vein posteriorly. In addition, one mobilizes the renal vein circumferentially from its entry into the inferior vena cava to the renal vein branches. The third key to mobilization of the pararenal aorta is resection of the autonomic ganglia on the left anterolateral aspect of aorta, surrounding the base of the superior mesenteric artery. The fourth key element of the exposure of the pararenal aorta is incision of the diaphragmatic crura on either side of the aorta. This permits vertical placement of an aortic clamp and obviates the need for full circumferential aortic exposure. The extent of the dissection of the renal arteries depends on whether a concomitant renal revascularization is to be performed. If a revascularization is to be undertaken, it is optimal to dissect the renal artery to its first bifurcation, whether an endarterectomy or bypass is to be performed. Exposure of the right renal artery can be facilitated by taking one or two lumbar vein branches.

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