Direct Surgical Repair for Celiac Axis and Superior Mesenteric Artery Occlusive Disease

Acute Mesenteric Ischemia

• Patients with acute mesenteric ischemia from embolus or in situ thrombosis require emergent definitive treatment. Extensive preoperative evaluation is potentially harmful because of the narrow window for salvaging the bowel. There is no role for nonoperative treatment.

• Heparin anticoagulation should be initiated to limit clot propagation and broad spectrum antibiotics administered that are effective against enteric organisms.

• Patients are frequently hypovolemic, and resuscitation should be initiated before the induction of anesthesia.

Chronic Mesenteric Ischemia

• Patients with chronic mesenteric ischemia should undergo expeditious medical and cardiac evaluation. However, a careful preoperative assessment is required to exclude other potential causes of chronic abdominal pain.

• Operative planning is facilitated by a computed tomography (CT) angiogram of the aorta and visceral vessels. Imaging is obtained to identify the extent of atherosclerotic occlusive disease, as well as the suitability of the supraceliac aorta as a site to originate an antegrade bypass, if required.

• Ankle-brachial indices and duplex imaging of the saphenous and femoral veins as potential conduits should be obtained.

• Patients with minimal postprandial pain should be counseled to avoid large meals or the specific food types that exacerbate their symptoms. Those with continuous abdominal pain should avoid oral intake with the exception of medications. Although the operative procedure should not be delayed in an attempt to replete nutritional stores, malnourished patients may be started on total parenteral nutrition if a somewhat prolonged preoperative course is anticipated.

• Preoperative bowel preparation is unnecessary.

Surgical Anatomy

There is an extensive collateral network among the celiac axis, superior mesenteric artery, inferior mesenteric artery, and internal iliac arteries. The celiac axis and superior mesenteric artery collateralize through the superior and inferior pancreaticoduodenal arteries, respectively, with the direction of flow contingent on the location of the stenosis. The superior and inferior mesenteric arteries collateralize through both the meandering artery and the marginal artery of Drummond. The meandering artery is the most significant collateral vessel and connects the ascending branch of the left colic artery with the middle branch of the middle colic artery. It lies at the base of the mesentery and is at risk of being ligated along with the inferior mesenteric vein during exposure of the infrarenal aorta. The inferior mesenteric artery communicates with the internal iliac artery via the hemorrhoidal branches and may represent a more important collateral than originally appreciated. This collateral pathway may be disrupted during sigmoid colectomy or infrarenal aortic aneurysm repair.

A significant amount of variability exists in the configuration of the visceral vessels. The “classic” three-vessel pattern for the celiac axis, consisting of the splenic, left gastric, and common hepatic arteries, occurs in approximately 75% of patients. Replaced or accessory hepatic arteries can originate from the superior mesenteric artery, and the left hepatic artery can arise off of the left gastric artery and course through the gastrohepatic ligament. A thorough review of preoperative imaging studies should be performed because both exposure and surgical planning for revascularization can be affected.

Acute Mesenteric Ischemia Secondary to Embolization, in Situ Thrombosis, and Dissection

Emboli responsible for acute mesenteric ischemia originate in the heart, usually as a result of atrial fibrillation, an acute myocardial infarction, or a ventricular aneurysm, and lodge in the superior mesenteric artery. Patients frequently have had a history of prior embolic events. Notably, an embolism to the superior mesenteric artery is quite large, in contrast to the micron-sized atheroembolic particles that cause blue toe syndrome. As a consequence, flow is easily restored in most situations by superior mesenteric artery embolectomy.

Acute mesenteric ischemia secondary to in situ thrombosis is superimposed upon the symptoms of chronic mesenteric ischemia in more than 50% of the patients. Patients with acute mesenteric ischemia secondary to in situ thrombosis require a mesenteric bypass. Although antegrade and retrograde bypasses are both options, retrograde bypass from the infrarenal aorta or iliac artery is the optimal procedure in the acute setting because of the ease of exposing the inflow source.

Dissections can occur in visceral vessels as an extension of an aortic dissection or, less commonly, as an isolated event. Mesenteric revascularization may be appropriate for patients with an acute aortic dissection and visceral malperfusion, but this approach is complicated by the underlying aortic pathology. Isolated or spontaneous dissections can occur in any visceral vessel, although the superior mesenteric artery appears to be the most common. The underlying cause or etiology remains unknown, although atherosclerosis, medial degeneration, trauma, fibromuscular disease, pregnancy, and a host of arteriopathies have been implicated. Patients’ symptoms may include abdominal pain. However, in one of the largest series in the literature, most patients were asymptomatic. The optimal treatment for an isolated dissection remains unresolved. Intervention is indicated for mesenteric ischemia, aneurysmal degeneration, and rupture. Both open and endovascular treatments have been reported, although the latter may be optimal given that the dissection can extend distally within the vessel. Expectant, conservative treatment with anticoagulation is likely adequate for asymptomatic or minimally symptomatic patients. Patients should be followed with serial CT imaging because of the risk of late aneurysmal degeneration. Similar to other vascular beds, these dissections can “heal” or resolve over time.

Selection of an Inflow Source

Mesenteric bypass, either antegrade from the supraceliac aorta or retrograde from the infrarenal aorta or common iliac artery, is indicated for patients with chronic mesenteric ischemia and those with acute mesenteric ischemia secondary to in situ thrombosis. The advantages of an antegrade bypass include the observation that the supraceliac aorta is usually free of atherosclerosis and the graft limbs follow a direct path while maintaining prograde flow. However, a retrograde bypass from the infrarenal aorta and common iliac artery is easier and faster to perform. Furthermore, although it is possible to partially occlude the supraceliac aorta while performing the proximal anastomosis of an antegrade bypass, the hemodynamic and ischemic impact of clamping the infrarenal aorta or iliac artery is minimal. One major disadvantage of a retrograde bypass is its potential to kink, which is particularly problematic for venous conduits. The graft must transition from the aorta that sits posterior in the abdomen to the superior mesenteric artery that sits more anterior. A ringed expanded polytetrafluoroethylene (ePTFE) conduit is a preferred choice. However, should a vein graft be required in the setting of enteric contamination, a relatively short conduit originating from the aorta, which is positioned to account for the normal lie of the superior mesenteric artery, should be considered.

Inherent to the debate about the type of bypass procedure is the number of vessels to be revascularized. Multivessel revascularization offers the advantage that if one graft limb occludes; the patient will not necessarily develop recurrent symptoms or acute mesenteric ischemia. Indeed, Hollier and colleagues reported that the rate of recurrent symptoms after open revascularization was inversely related to the number of vessels revascularized. Proponents of an isolated retrograde bypass to the superior mesenteric artery emphasize that the procedure revascularizes the primary vessel of concern, multivessel reconstruction significantly increases the complexity of the procedure, and more recent series have not demonstrated a clinical advantage for multivessel bypass.

Selection of the Celiac Artery Outflow SITE: Main Celiac Trunk or Common Hepatic Artery

Either the main celiac artery trunk or the common hepatic artery may be used as the outflow site for an antegrade bypass. The atherosclerotic occlusive process is essentially “aortic spillover” disease that affects the proximal portion of the vessel and usually extends to the first branch. Both options have relative advantages and disadvantages. Using the main celiac trunk facilitates an end-to-end anastomosis with a generous anastomosis given its larger size. In contrast, the common hepatic is more superficial to expose, although it is more difficult to orient the graft and the artery to configure the anastomosis.