Residency · Residency · Interventional Radiology

Mesenteric Ischemia: Acute and Chronic Management

Mesenteric Vascular Anatomy

The gut is supplied by three major mesenteric arteries. The celiac artery arises from the aorta at the level of T12 and supplies the foregut structures: the stomach, liver, spleen, proximal duodenum, and pancreas. The superior mesenteric artery (SMA) originates at L1 and supplies the midgut, from the distal duodenum to the splenic flexure of the colon. The inferior mesenteric artery (IMA) arises at L3 and supplies the hindgut, from the splenic flexure to the upper rectum.

Several collateral pathways interconnect these territories. The pancreaticoduodenal arcades bridge the celiac and SMA territories. The arc of Riolan, also known as the meandering mesenteric artery, and the marginal artery of Drummond both connect the SMA and IMA along the mesenteric border of the colon. The arc of Buhler is a rare persistent ventral anastomosis between the celiac and SMA. Two watershed areas are clinically important: the splenic flexure (Griffiths point) and the rectosigmoid junction (Sudeck point), where collateral perfusion is most tenuous.

Acute Mesenteric Ischemia (AMI)

Etiologies

Arterial embolism accounts for 40 to 50 percent of AMI cases. It usually originates from a cardiac source such as atrial fibrillation or mural thrombus and typically lodges at an SMA branch point distal to the origin of the middle colic artery, which often spares the proximal jejunum. Arterial thrombosis is responsible for 20 to 30 percent of cases and involves acute thrombosis of a pre-existing atherosclerotic stenosis, usually at the SMA origin; these patients frequently have a history of chronic mesenteric ischemia symptoms. Non-occlusive mesenteric ischemia (NOMI) accounts for approximately 20 percent and results from mesenteric vasospasm in the setting of low cardiac output, vasopressor use, or shock, without any mechanical obstruction. Mesenteric venous thrombosis makes up 5 to 15 percent and involves thrombosis of the superior mesenteric vein or portal venous system, associated with hypercoagulable states, portal hypertension, or malignancy.

Clinical Presentation

The classic finding is "pain out of proportion to physical examination," meaning severe periumbilical pain with minimal tenderness in the early stages. Patients may also have nausea, vomiting, and diarrhea that may be bloody. Without treatment, clinical deterioration is rapid, progressing to peritonitis, sepsis, and multiorgan failure. Elevated lactate, leukocytosis, and metabolic acidosis are late findings that indicate bowel necrosis has already occurred. Mortality remains 60 to 80 percent once bowel infarction develops.

Diagnostic Imaging

CT angiography is the diagnostic study of choice. The arterial phase identifies SMA occlusion or filling defects and mesenteric vessel calcification. The venous phase identifies venous thrombosis. Bowel-related findings include wall thickening, pneumatosis intestinalis, portal venous gas, and mesenteric stranding, with pneumatosis and portal venous gas suggesting transmural necrosis. Catheter angiography is reserved for situations where simultaneous diagnosis and intervention are planned.

Management by Etiology

Arterial Embolism

Immediate anticoagulation with heparin is the first step. Endovascular options include catheter-directed thrombolysis, aspiration thrombectomy, or pharmacomechanical thrombectomy. The SMA is catheterized via a transfemoral approach, and aspiration using a system such as the Indigo is performed, followed by infusion if residual thrombus persists. The surgical option is open embolectomy using a Fogarty catheter via an SMA arteriotomy, which allows direct assessment of bowel viability. A second-look laparotomy at 24 to 48 hours is performed to reassess bowel viability.

Arterial Thrombosis

When thrombosis occurs at the SMA origin over pre-existing atherosclerosis, the endovascular approach involves SMA angioplasty and stenting, which may require wire escalation for an ostial chronic total occlusion. The surgical approach involves aortomesenteric bypass, either antegrade or retrograde, with bowel resection as needed. Mortality is higher than in embolic AMI because bowel involvement tends to be more extensive.

Non-Occlusive Mesenteric Ischemia (NOMI)

The priority is hemodynamic optimization through volume resuscitation and reduction or elimination of vasopressors when possible. Selective SMA catheterization allows direct vasodilator infusion, typically papaverine at 30 to 60 mg per hour or prostaglandin E1, via an indwelling SMA catheter. There is no mechanical obstruction to treat; the intervention is purely pharmacologic. Surgery is indicated for peritonitis or bowel necrosis.

Mesenteric Venous Thrombosis

Systemic anticoagulation is the primary treatment. For extensive SMV or portal vein thrombosis, catheter-directed thrombolysis can be performed via a transjugular transhepatic approach. TIPS can be combined with mechanical thrombectomy for portal or SMV thrombosis. Surgery is reserved for cases with peritonitis.

Chronic Mesenteric Ischemia (CMI)

Pathophysiology

Chronic mesenteric ischemia results from atherosclerotic stenosis of the mesenteric arteries. Because of the extensive collateral network, two or three vessels typically must be affected before symptoms develop. Postprandial abdominal pain, sometimes called "intestinal angina," occurs because blood flow cannot increase sufficiently to meet the metabolic demands of digestion. The classic triad is postprandial abdominal pain, food aversion (sitophobia), and weight loss.

Diagnosis

CTA or MRA identifies stenosis or occlusion of the celiac and SMA origins. Duplex ultrasound serves as a screening tool, with an SMA peak systolic velocity greater than 275 cm/s suggesting more than 70 percent stenosis and a celiac PSV greater than 200 cm/s raising similar concern. Catheter angiography, with lateral aortography being essential for evaluating ostial disease (an anteroposterior view may miss ostial stenoses), remains the definitive study. Imaging findings must always be correlated with clinical symptoms, since anatomic stenosis alone is insufficient for diagnosis.

Endovascular Revascularization

SMA stenting is the primary treatment at most centers. A balloon-expandable stent is preferred for ostial lesions because of its precise placement and greater radial force, typically 6 to 7 mm in diameter and 15 to 18 mm in length. Access can be transfemoral or transbrachial/transradial, with brachial access providing a more favorable angle for SMA catheterization. Celiac stenting is performed when the celiac is the primary symptomatic vessel or when improving collateral flow is desired, though median arcuate ligament syndrome must be ruled out first, since extrinsic compression will cause stent compression. Technical success exceeds 95 percent, with clinical success ranging from 80 to 90 percent. The main limitation is in-stent restenosis, which occurs in 20 to 40 percent of cases at 3 years and requires surveillance duplex follow-up.

Surgical Revascularization

Surgical options include aortomesenteric bypass using saphenous vein or prosthetic conduit, either in an antegrade or retrograde configuration, and mesenteric endarterectomy. Long-term patency is superior compared with endovascular approaches. Surgical revascularization is reserved for patients who fail endovascular therapy, young patients, or those with complex anatomy involving multiple vessel disease or aortic disease.

Median Arcuate Ligament Syndrome (MALS)

Median arcuate ligament syndrome involves extrinsic compression of the celiac artery by the median arcuate ligament of the diaphragm. The stenosis is dynamic and worsens with expiration. MALS is a controversial entity because many asymptomatic individuals demonstrate celiac compression on imaging. Treatment involves surgical ligament release, performed either open or laparoscopically, followed by stenting if residual stenosis persists. A celiac artery compressed by the ligament should never be stented without ligament release first, because the stent will be compressed and will fail.

<image>Anatomic illustration of the mesenteric arterial system and collateral pathways. An anterior view showing the celiac artery with its branches (left gastric, common hepatic, splenic), the superior mesenteric artery with its branches (inferior pancreaticoduodenal, jejunal, ileal, ileocolic, right colic, middle colic), and the inferior mesenteric artery with its branches (left colic, sigmoidal, superior rectal). The pancreaticoduodenal arcade connecting the celiac and SMA is highlighted. The marginal artery of Drummond and the arc of Riolan connecting the SMA and IMA are shown. Watershed areas at the splenic flexure and rectosigmoid junction are marked with asterisks.</image>

<image>CT angiography findings in acute mesenteric ischemia. Four panels: (1) Axial CTA showing a filling defect (embolus) in the SMA with abrupt cutoff of contrast; (2) Coronal reformatted image showing the SMA embolus lodged distal to the middle colic artery origin; (3) Axial image showing pneumatosis intestinalis of the small bowel wall with portal venous gas in the liver (arrows); (4) Sagittal CTA showing chronic atherosclerotic stenosis at the SMA and celiac origins in a patient with chronic mesenteric ischemia. Labels identify each finding and its clinical significance.</image>

<image>Illustration of endovascular treatment of SMA stenosis for chronic mesenteric ischemia. Three sequential panels: (1) Lateral aortogram showing high-grade ostial stenosis of the SMA and celiac artery; (2) Balloon-expandable stent deployment at the SMA origin via a transfemoral approach, with a magnified inset showing the stent bridging from the aorta into the SMA (1-2 mm protrusion into the aortic lumen); (3) Post-stenting lateral aortogram showing restored SMA flow with widely patent stent. The celiac artery compression by the median arcuate ligament is illustrated in a companion panel with a note that stenting alone is not appropriate for MALS.</image>

Clinical Pearls

Acute mesenteric ischemia is a surgical emergency where "time is bowel," and early CTA with prompt intervention is essential. The classic presentation of pain out of proportion to examination is often absent in ICU patients and the elderly, so a high index of suspicion must be maintained. Elevated lactate and metabolic acidosis are late findings that indicate bowel necrosis; treatment should not be delayed waiting for these markers. In embolic AMI, the proximal jejunum is often spared because the embolus lodges distal to the first jejunal branch. For chronic mesenteric ischemia, lateral views during angiography are essential because ostial stenoses are not visible on anteroposterior projections. A celiac artery compressed by the median arcuate ligament should never be stented without surgical release first. Typically, two or more mesenteric vessels must be diseased before CMI symptoms develop, thanks to the rich collateral network.

References

• Defined by the ACR Appropriateness Criteria for Acute Mesenteric Ischemia, Radiology 2020
• Defined by the ESVS Clinical Practice Guidelines on Mesenteric Artery Disease, Eur J Vasc Endovasc Surg 2017
• Defined by the American Gastroenterological Association Technical Review on Management of Mesenteric Ischemia, Gastroenterology 2000
• Defined by Defined by Defined by the SVS Clinical Practice Guidelines on CMI. J Vasc Surg 2021

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