The celiac axis and mesenteric arteries are the principal sources of blood supply to the stomach and intestines, with the two internal iliac arteries adding collateral flow to the distal colon. The anatomic collateral interconnections between these arteries are numerous. Single or even multiple visceral artery lesions are generally well tolerated, because collateral flow is readily available.
Atherosclerosis is the cause of obstructive lesions in the visceral arteries in the vast majority of cases. Vasculitis (eg, lupus erythematosus, Takayasu’s disease) is the second most common cause. When atherosclerosis is the cause, the usual lesion is a collar of plaque that creates a proximal stenosis or occlusion. Associated atherosclerosis in the aorta and its other branches is common.
Acute mesenteric ischemia is a complex, highly morbid disorder. Patients classically present with excruciating diffuse abdominal pain with a surprising absence of physical findings such as abdominal tenderness or distention—unless actual bowel perforation produces a surgical abdomen. The cause is either embolic or thrombotic. The diagnosis can be difficult and its recognition is often delayed, resulting in irreversible bowel ischemia. The mortality rate from mesenteric ischemia remains high. Patients who require massive bowel resection rarely survive or, if they survive, can develop incapacitating short-gut syndrome. The prognosis improves dramatically if revascularization can be achieved prior to intestinal infarction. This obviously requires early diagnosis, which will only occur if the practitioner has a high index of suspicion.
Visceral ischemia due to compression of the celiac artery (median arcuate ligament syndrome) is an unusual cause of visceral ischemia. It generally affects young adults, with women more commonly affected than men. The artery is scarred and must be repaired in conjunction with release of the compressing ligament. The diagnosis is difficult to make with certainty as some compression by the arcuate ligament is common. Surgery should be advised only after a search for other causes of postprandial pain.
The principal complaint is postprandial abdominal pain, which has been labeled abdominal or visceral angina. Pain characteristically appears 15–30 minutes after the beginning of a meal and lasts for an hour or longer. Pain is occasionally so severe and prolonged that opiates are required for relief. Pain occurs as a deep-seated steady ache in the epigastrium, occasionally radiating to the right or left upper quadrant. Weight loss results from reluctance to eat, although mild degrees of malabsorption can occur. Thus, gastrointestinal absorption studies are not helpful. Diarrhea and vomiting have been described. An upper abdominal bruit may be heard in over 80% of patients.
Arteriography in the anteroposterior and especially the lateral projections demonstrates both the arterial lesion and the patterns of collateral blood flow. Patients should be well hydrated before angiography because this procedure can precipitate hypercoagulability and osmotic diuresis with dehydration, vascular occlusion, and bowel infarction. Duplex scanning and MRA are used with increasing frequency because they are less invasive methods of screening.
Treatment of Gastrointestinal Ischemia Syndromes
When the obstruction is atherosclerotic, revascularization of the superior mesenteric and celiac axes may be performed by either endarterectomy or graft replacement. During endarterectomy, a sleeve of aortic intima and the orifice lesions in the celiac or superior mesenteric arteries are removed. The operation is performed by a retroperitoneal approach to the aorta through a left thoracoabdominal incision.
In addition, PTA and stenting has gained acceptance as an alternative form of therapy.
Surgery for atherosclerotic visceral artery insufficiency almost always results in relief of symptoms if a technically adequate operation is accomplished. If operation is not performed, death will occur from inanition or massive bowel infarction.
Patients with median arcuate ligament compression respond favorably to operation in the majority of instances; however, some of these patients are not improved even though a technically adequate operation is performed.