As the descending thoracic aorta crosses the diaphragm and courses into its retroperitoneal location, becoming the abdominal aorta, it passes through the aortic hiatus. This defect in the diaphragm is bounded anteriorly by the medial arcuate ligament which has left and right crura, then inserts on the spine behind the aorta on the T12 vertebra. The celiac artery originates off the anterior wall of the aorta almost immediately after it passes through the aortic hiatus, and in certain situations is subject to compression by the arcuate ligament, resulting in celiac artery compression syndrome (CACS), also known as median arcuate ligament (MAL) syndrome. Understanding the anatomy of the aortic hiatus and its relationship to the aorta is a basic requirement for an accomplished aortic surgeon, since the ability to identify and manage the diaphragmatic crura is important in several instances besides the surgical management of CACS. These instances include the rapid exposure and clamping of the supraceliac aorta during the open repair of a ruptured abdominal aortic aneurysm, as well as the exposure of the suprarenal or supraceliac aorta during the elective repair of juxta- or suprarenal aneurysms, or during aortomesenteric bypasses which originate off the supraceliac aorta.

The hallmark of CACS is intermittent compression of the celiac artery origin by the MAL, most easily observed on imaging studies during expiration as the abdominal organs rise in the abdomen and the angle between the CA and aorta becomes more acute. The most rational pathophysiologic mechanism is based on arterial ischemia, from either direct malperfusion of the organs perfused by the celiac artery, or secondary malperfusion of the small bowel due to diversion of blood flow from the superior mesenteric artery (SMA) circulation to the celiac artery circulation when the celiac
artery is malperfused, via the known collaterals (gastroduodenal artery, pancreaticoduodenal arteries) that exist between these two vascular beds. Malperfusion of the SMA circulation will routinely cause intestinal angina, and recent studies have shown that isolated malperfusion of the celiac artery can produce symptomatic ischemia. In addition, gastric tonometry studies have shown that the gastric mucosa is ischemic in CACS. An alternate theory that has been suggested is that pain in CACS is mediated by compression and irritation of the periaortic neural plexus, and some authors have proposed ganglionectomy as an important component of therapy for CACS. However, clinical and experimental evidence for this theory is lacking.

With respect to CACS, treatment is indicated in cases of intractable pain in patients with angiographic evidence of celiac compression syndrome, and no other identifiable etiology for their pain after a complete set of abdominal investigations performed under the supervision of a gastroenterologist. Patients typically complain of right upper quadrant or epigastric pain that is related to eating or activity, and may radiate to the back. Significant weight loss and fear of food is not as common as it is with atherosclerotic mesenteric occlusive disease but most patients report weight loss. The common diagnoses of small bowel obstruction, gastric dysmotility, peptic ulcer disease, inflammatory bowel disease, biliary and pancreatic diseases, malabsorption, and symptomatic nephrolithiases must be ruled out. Prerequisite studies include an upper GI series and small bowel follow through, hepatic ultrasound, upper and lower endoscopy, CT scan, and testing for malabsorption. Patients are usually referred for consideration of treatment after this set of abdominal investigations mentioned above is negative, except for the suggestion of celiac compression identified on either a duplex ultrasound or CT scan. An astute vascular lab technologist may identify celiac compression when performing a mesenteric arterial ultrasound, but the provocative testing required to confirm this diagnosis is not a standard component of a mesenteric duplex, so the absence of this diagnosis from a report of a mesenteric duplex should not rule out this diagnosis. Moreover, mesenteric arterial studies are the most technically challenging studies of all those performed by ultrasound technologists due to the depth of the region of interest, and the overlying structures including the stomach, colon, and rib cage which can obscure the arteries being studied.

Gastric tonometry is a physiologic test which is capable of detecting gastric ischemia. An abnormal preoperative gastric tonometry study predicts a successful outcome with celiac artery decompression, and the study will normalize after successful decompression. Ideally every patient who is being considered for celiac artery decompression should undergo a gastric tonometry study, but unfortunately this specialized test is not available at most institutions.

Dynamic compression of the celiac artery is accompanied by a fixed intrinsic stenosis in the celiac artery in at least 25% of cases. Identifying a fixed intrinsic stenosis represents the most important consideration in preoperative planning since the treatment of a fixed lesion greatly affects the risk of the procedure and may alter the surgical approach. Preoperative stenting is contraindicated in CACS, as it is in other compressive syndromes, since stents are prone to fracture. Postoperative stenting of a celiac stenosis after surgical decompression is an option and in the author’s experience can be accomplished in most instances, but the disadvantages of postoperative stenting include the fact that it may be technically impossible to stent a tight stenosis, and there is a higher risk of restenosis with stenting. Complete occlusions of the celiac artery are usually completely refractory to stenting. Surgical treatment of an intrinsic stenosis with either endarterectomy or bypass at the time of decompression is preferable in most instances, but does greatly increase the operative risk of the procedure compared to simple decompression. Postoperative stenting is a reasonable approach if laparoscopic decompression is being considered, since arterial reconstruction is contraindicated with laparoscopic decompression; complex arterial reconstructions cannot be safely performed with currently available laparoscopic technology.

It is therefore critical to identify an intrinsic stenosis of the celiac artery preoperatively. Although CT scanning is an effective modality to image the aorta and visceral branches, a modified scan is required to image the celiac artery during inspiration and expiration. The gold standard for preoperative imaging remains selective mesenteric angiography, which can provide detailed images of the celiac artery origin with celiac artery catheterization, and also demonstrate shunting of blood flow from SMA to the celiac artery with SMA catheterization. Angiography is also more sensitive at identifying subtle abnormalities such as aberrant anatomy or vasculitis. Therefore, mesenteric angiography is recommended preoperatively with selective catheterization of both the celiac artery and superior mesenteric artery and imaging both arteries in inspiratory and expiratory phases.

There are five different approaches to the aortic hiatus: