Figure 91-9. Nonocclusive mesenteric ischemia – mesenteric arteriogram revealing diffuse vasoconstriction and nonopacification of

SMA branch vessels.

CHRONIC MESENTERIC ISCHEMIA

Symptoms of CMI are often referred to as “intestinal angina.” Ostial stenosis secondary to

arteriosclerosis is the most common etiology and patients typically share risk factors of overt

atherosclerosis and long-standing tobacco abuse. Additional causes of CMI may include arterial FMD,

vasculitis, aortic coarctation, and connective tissue disorders. In light of aforementioned mesenteric

collaterals, the responsible anatomic lesions of CMI typically affect at least two of three splanchnic

arteries, although isolated lesions of the SMA distal to the middle colic branch may yield intestinal

angina by excluding collateralization.2 Patients classically present with postprandial abdominal pain that

occurs within 30 minutes of eating and may last up to 4 hours postprandial. Consistent postprandial

symptoms typically result in the modification of eating habits that may range from the consumption of

smaller meals to “food phobia” that subsequently results in weight loss and malnutrition.

5 The progression from minor symptoms to AMI and intestinal infarction is unpredictable; almost half

of patients presenting with AMI describe previous symptoms of CMI.46 The incidence of CMI also

remains unclear. Population studies suggest that up to 18% of individuals over 65 years of age have

asymptomatic radiographic mesenteric stenosis.47 Duplex ultrasonography should be considered the

first-line diagnostic modality for CMI. Specifically, high-grade stenosis of the SMA and celiac artery in a

fasting state are suggested by a peak systolic velocity of >275 cm/s and 200 cm/s, respectively.48 CTA

and MRA support the diagnosis of CMI while offering additional vascular anatomic evaluation such as

the presence of aortic aneurysm, calcific burden, and venous anomalies that may impact open

reconstruction. Aortography with anteroposterior and lateral views has been commonly cited as the

gold standard for diagnosis and allows for simultaneous mesenteric arteriography, manometry,

provocative measures (i.e., vasodilator infusion), and intervention (i.e., angioplasty and stenting) as

appropriate. This modality is often favored over cross-sectional imaging when an endovascular approach

for treatment is being considered over open revascularization. Often patients will present having

undergone extensive gastrointestinal work-up (i.e., contrast motility studies, endoscopy, and

laparotomy) before the diagnosis of CMI is considered.

MANAGEMENT OF CMI

Treatment goals in the management of CMI include symptomatic relief, restoration of normal weight,

and the prevention of bowel infarction. Mesenteric revascularization provides immediate symptom

relief in most patients. Classically, open surgical revascularization options consider patient

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cardiopulmonary reserve to tolerate aortic cross-clamping and aortic and arterial calcific burden to

dictate vascular sites for clamping and sewing. Elective revascularization in the lower-risk patient favors

two-vessel (i.e., celiac and SMA) antegrade reconstruction when anatomically feasible. Contingent on

vessel calcification, the supraceliac aorta through a transperitoneal approach serves as a preferential

target for inflow. After entering the lesser sac, division of the left triangular ligament allows for

retraction of the left hepatic lobe. With the esophagus retracted toward the patient’s left (confirmed by

palpation of the existing nasogastric tube), transection of the diaphragmatic crura exposes the

supraceliac aorta. The celiac trunk, common hepatic artery, and splenic artery are exposed at this time.

Subsequently with retraction of the transverse mesocolon cephalad, the SMA is exposed as described

above at the root of the mesentery. A retropancreatic tunnel is created that courses anterior to the renal

vein. The patient is systemically anticoagulated with heparin and the proximal anastomosis can be

constructed with partial aortic occlusion. Most often a knitted polyester synthetic graft is utilized for

conduit. There are multiple acceptable variations that include the use of two separate aortomesenteric

bypass grafts (Fig. 91-10) or the use of a bifurcated graft. It is conventional to utilize a prefabricated

bifurcated graft (e.g., 14 × 7 mm) for reconstruction. In this case a short main body is beveled to

create the proximal end-to-side aortic anastomosis; the left limb is tunneled through the retropancreatic

tunnel and an end-to-side distal anastomosis created next to the SMA; the right limb is subsequently cut

to size and beveled to create an end-to-end anastomosis to the celiac artery directly or an end-to-side

anastomosis with the common hepatic artery. These authors favor the approach presented in Figure 91-

11. A limb of a bifurcated knitted polyester graft is transected off the main body in such a way that

there is a phalange created. This limb is specifically utilized for creation of the aorto-SMA bypass, with

the phalange incorporated into the proximal aortic anastomosis as shown. The remaining limb is cut to

size and beveled accordingly; the proximal anastomosis is constructed end-to-side off the aorto-SMA

bypass graft and the distal anastomosis constructed end-to-side to the common hepatic artery. This

facilitates a very short celiac limb with a natural lie that may reduce the risk of limb kinking or torsion.

Finally, the descending thoracic aorta may serve as an alternative source for inflow when supraceliac

aortic anatomy is prohibitive or has previously been utilized for revascularization (Fig. 91-12). For

those patients with comorbidity or anatomy (i.e., calcification) that precludes aortic clamping, a

retrograde ilio-SMA bypass is favored as described above (Fig. 91-9).

Transaortic endarterectomy is less often utilized in contemporary practice, but may be applicable for

those patients with bowel perforation or contamination, hostile abdominal conditions (extensive

adhesive disease or abdominal wall hernia), and bulky coral reef aortomesenteric plaque with lower

extremity ischemia. A retroperitoneal approach to the perivisceral aorta through a thoracoabdominal

incision permits a longitudinal or trapdoor aortotomy, endarterectomy and repair with primary closure

or patch aortoplasty as illustrated in Figure 91-13.

Figure 91-10. Two-vessel antegrade aortomesenteric bypass.

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Figure 91-11. Two-vessel antegrade aortomesenteric bypass based off the supraceliac aorta using a presewn bifurcated graft.

Figure 91-12. Two-vessel antegrade aortomesenteric bypass based off the supraceliac aorta using two separate grafts.

While historically criticized for high mortality rates (up to 15%), contemporary outcomes following

open mesenteric bypass at high-volume centers support mortality rates <4%, likely secondary to

technical refinements, improved patient selection and advances in medical, anesthetic, and critical care

management.49–56 Open mesenteric revascularization boasts excellent symptom improvement (77% to

100%) with low recurrence rates at 3 to 5 years (0% to 32%) and perioperative morbidity rates

approximating 35% to 40%.56,57

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Figure 91-13. Endarterectomy of the aorta, celiac and superior mesenteric arteries through a longitudinal trapdoor aortotomy with

primary closure.

Endovascular mesenteric revascularization has increasingly become utilized for chronic mesenteric

ischemia. Stenting of the mesenteric vessels is recommended over angioplasty alone for favorable

anatomy that includes short segment SMA stenosis (<2 cm) with minimal to moderate calcification or

thrombus, although some authors support a role for stenting in the treatment of higher-risk and

occluded vessels.58,59 Endovascular revascularization offers success rates approaching 100% with

immediate symptom relief. While perioperative morbidity is notably lower in comparison to open

surgical revascularization, endovascular interventions are more likely to result in restenosis, recurrent

symptoms, and require reintervention.53,60–62 Primary and secondary patency rates approximate 40%

and 88%, respectively at 5 years (in comparison to 88% and 97% following open revascularization)

emphasizing the importance of patient counseling preoperatively and close surveillance

postprocedure.56 Two-vessel (celiac and SMA) stenting does not appear to reduce the risk of recurrent

symptoms or reintervention when compared to single-vessel (SMA) stenting and moreover, isolated

celiac artery stenting carries a higher risk of recurrence.63 Covered stents appear to be associated with

less restenosis, recurrence, and reintervention in comparison to bare metal stents.64

A large review of mesenteric revascularization from the Nationwide Inpatient Sample between 1988

and 2006 demonstrated increased overall revascularization procedures for CMI.65 Additionally, these

authors noted that mesenteric angioplasty and stenting not only surpassed open revascularization

procedures for CMI in 2002, endovascular interventions more than doubled open procedures by 2005.

While endovascular interventions may be associated with decreased mortality, shorter hospital length of

stay, and decreased perioperative morbidity, the data are clouded by both the expansion of treatment

indications and the fact that a greater risk of restenosis and recurrent symptoms may increase overall

interventions. Moreover, these reinterventions for recurrence likely carry a variable risk for in-hospital

morbidity and mortality. Regardless, mesenteric stenting has become the first-line therapy for most

patients with atherosclerotic CMI and maintains an important role as a temporizing measure to facilitate

weight gain in the high-risk malnourished patients (as a bridge to open revascularization) and for those

patients with medical comorbidities that would further complicate or prohibit open surgical

revascularization.

Median Arcuate Ligament Syndrome

Median arcuate ligament syndrome (MALS) remains a controversial diagnosis, first described in the

1960s.66 Chronic abdominal pain is associated with radiographic evidence of celiac artery compression

by the overlying fibrous arch of the MAL and adjacent celiac ganglion. The pathophysiology remains

poorly understood and evidence suggests both ischemic and neurogenic etiologies for pain.67 Gastric

tonometry has documented evidence of mucosal ischemia in patients prior to treatment.68 The 7% to

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21% incidence of celiac artery compression in asymptomatic patients combined with the typical robust

mesenteric collaterals and widely patent superior and inferior mesenteric arteries present in these

younger individuals favor a neurogenic etiology.69,70 Specifically, compression of the celiac plexus

somatic nerves by the MAL may produce abdominal pain that is improved with a celiac ganglionectomy

that accompanies ligament release or percutaneous celiac plexus block.

Patients with MALS are typically females in their third decade of life. Symptoms most commonly

include postprandial pain, weight loss, and less commonly nausea and diarrhea. Diagnosis is supported

by duplex ultrasonography that demonstrates elevated peak systolic velocities through the celiac artery

on expiration that normalize or improve with inspiration and reverse flow through the hepatic artery.71

Cross-sectional imaging like CTA and MRA can support the diagnosis as well, and may reveal

poststenotic dilation of the celiac artery. Angiography demonstrating dynamic compression or occlusion

during peak expiration remains the gold standard for the diagnosis of MALS (Fig. 91-14). Additionally,

as MALS remains a diagnosis of exclusion, some authors favor gastric exercise tonometry test and celiac

ganglion block to support patient selection.72

Release of the MAL should include complete dissection and skeletonization of both the MAL and

surrounding nerve ganglion. This can be accomplished through an open approach whereby the aortic

hiatus and celiac artery are exposed through the lesser sac. Additionally, laparoscopic and more recently

robotic techniques have been described. The most contemporary literature review and large series

suggest immediate postoperative symptoms relief in approximately 80% to 90% of patients.67,68,73–78

Adjunctive procedures for celiac artery revascularization are utilized in a minority of cases and may

include celiac angioplasty, celiac artery patch angioplasty, and celiac artery bypass (i.e., aortoceliac

bypass). Late symptom recurrence approximates 6% and only Reilly and colleagues have demonstrated

a reduction in recurrence following MAL release with celiac artery revascularization in comparison to

MAL release alone (24% vs. 44%).67,79 Multiple authors have highlighted the importance of patient

selection for treatment suggesting that specific patient criteria may correlate with successful outcomes

including: consistent postprandial abdominal pain, young age, female gender, weight loss >20 lb and

anatomic features of poststenotic dilation or increased collateral flow.79–81 A reasonable approach may

reserve adjunctive revascularization for those patients with objective angiographic pressure or

ultrasound velocity gradients following open surgical MAL decompression or those with persistent

symptoms following laparoscopic or robotic release.

Figure 91-14. Lateral aortography demonstrating (A) external compression (arrow) of the celiac artery on peak inspiration that (B)

worsens dynamically (arrow) during peak expiration.

Laparoscopic release of the MAL is increasingly employed for MALS.67,73,77,78 While no procedurerelated mortality has been reported for open or laparoscopic ligament release, there is a 9.1% incidence

across series of open conversion for hemorrhage that follows laparoscopic release, which heightens

morbidity and mortality risk.67 Certainly independent operator learning curve, institutional technical

enhancements, and patient selection may strongly affect this result. More recently, safe and effective

robotic-assisted MAL release has been reported to offer benefits over laparoscopic release in light of

improved visualization, extra degree of motion provided by robotic arms with “wrist movement” and

scaled operator movements (including tremor elimination).82

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