Chronic Mesenteric Ischemia, MALS, and Mesenteric Arterial Dissection

49.1Definition and clinical presentation

Chronic mesenteric ischemia (CMI) is a clinicoradiologic diagnosis defined by symptomatic intestinal hypoperfusion and significant mesenteric arterial obstruction. Because the celiac artery, superior mesenteric artery (SMA), and inferior mesenteric artery (IMA) share robust collateral networks, symptomatic CMI typically reflects multivessel atherosclerotic disease Anandan 2012.

The classic presentation features:

• Postprandial abdominal pain, typically predictable in onset after eating.
• Food fear and reduced meal size.
• Unexplained weight loss.

Symptoms are suggestive rather than specific, frequently prompting extensive evaluation for functional or structural gastrointestinal disease before a vascular diagnosis is established European CMI · 2020 · Anandan 2012. Acute-on-chronic mesenteric ischemia presents with a sudden escalation in symptom severity or a new pain pattern. This presentation shifts the pathology from an elective revascularization problem to a bowel-viability emergency, requiring urgent imaging and operative evaluation Rebelo 2022.

49.2Diagnosis and anatomic evaluation

A definitive diagnosis requires symptom-anatomy correlation and exclusion of competing gastrointestinal pathology. Multidisciplinary evaluation incorporating vascular surgery, interventional radiology, gastroenterology, and dietetics optimizes case selection and nutritional assessment European CMI · 2020.

Computed tomography angiography (CTA) provides essential anatomic mapping, defining ostial origins, lesion length, calcification, distal target vessels, and collateral pathways. Mesenteric duplex ultrasound confirms hemodynamic significance. A peak systolic velocity greater than 275 cm/s in the SMA supports an anatomic stenosis greater than 70%, establishing the functional severity of the lesion European CMI · 2020 · Anandan 2012. The companion celiac-axis cutoff is a peak systolic velocity of 200 cm/s or greater, or an end-diastolic velocity above 55 cm/s, indicating celiac stenosis of 70% or greater; both vessels are interrogated because CMI is multivessel disease and the celiac artery is one of the two diagnostically pivotal targets. Frailty scoring and dietetic assessment are performed at diagnosis, as profound malnutrition embedded in the disease increases the hazard of intervention Lai 2024 · Wolk 2022.

49.3Treatment thresholds and revascularization

Intervention is indicated for symptomatic CMI confirmed by significant anatomic and hemodynamic obstruction. The SMA is the primary revascularization target: it supplies the postprandial intestinal bed most directly, and restoring SMA inflow most often determines durable symptom relief European CMI · 2020. Incidental asymptomatic stenosis is managed conservatively, with individualized exceptions for patients planned for major abdominal surgery that may disrupt established collateral pathways. Systemic atherosclerosis medical therapy, including statin administration, antiplatelet therapy, blood-pressure control, and smoking cessation, is initiated at diagnosis Wolk 2022.

The treatment decision follows an ordered algorithm:

1. Competing gastrointestinal diagnoses are excluded and symptom-anatomy correlation is confirmed.
2. Optimal medical therapy and nutritional repletion are initiated.
3. Endovascular revascularization is selected as the default for elderly, malnourished, or high-risk patients to minimize early procedural morbidity, accepting a higher risk of restenosis and reintervention.
4. Open mesenteric bypass (offering 5-year primary patency of 80 to 90%) is selected for fit, younger patients, or those with long-segment occlusions, recurrent disease, or calcification unsuitable for stenting, prioritizing long-term durability over initial operative morbidity.

49.4Median arcuate ligament syndrome

Median arcuate ligament syndrome (MALS) is a distinct entity characterized by postprandial pain, weight loss, nausea, and dynamic celiac-axis compression by the median arcuate ligament. It is most frequently diagnosed in young women. Precision anatomic evaluation requires CTA with dynamic phases, duplex assessment with respiratory variation, and celiac plexus assessment AOB Consensus 2026.

Surgical release of the median arcuate ligament is indicated for highly selected patients meeting specific diagnostic criteria with negative functional and structural gastrointestinal evaluations. Minimally invasive and robotic platforms achieve effective symptom relief and shorter hospital stays compared to open release Birkhold 2022 · Fernstrum 2020. Objective mesenteric ischemia is uncommon in this population, and surgical success is measured by symptom resolution rather than physiological flow restoration AOB Consensus 2026 · AOB Consensus 2026.

49.5Isolated visceral artery dissection

Spontaneous isolated dissection of the SMA or celiac artery presents with acute or chronic abdominal pain mimicking occlusive ischemia. CTA distinguishes the dissection morphology from atherosclerosis. Initial management of uncomplicated isolated dissection is conservative, using antithrombotic therapy (antiplatelet or anticoagulation) and serial imaging surveillance Ullah 2019 · Zhang 2025.

Endovascular therapy is reserved for patients with persistent malperfusion, progressive symptoms, or an expanding false lumen. Open surgical reconstruction is a bailout option when endovascular techniques fail. Most conservatively managed patients demonstrate radiologic stability or resolution on follow-up imaging Ullah 2019 · Satokawa 2019.

49.6Surveillance and follow-up

Post-revascularization surveillance tracks symptoms, weight, dietary tolerance, and structural patency. Following endovascular CMI therapy, mesenteric duplex is scheduled at 1, 3, 6, and 12 months, and annually thereafter European CMI · 2020 · Yu 2022. Early detection of in-stent restenosis facilitates preemptive reintervention before symptomatic relapse and recurrent malnutrition occur.

Symptom recurrence requires careful interpretation. Renewed food fear, weight loss, and postprandial pain warrant prompt CTA and duplex imaging. Conversely, vague dyspepsia without weight loss requires gastrointestinal evaluation before presuming technical failure European CMI · 2020 · Menges 2020. Follow-up of conservatively managed visceral artery dissection relies on scheduled imaging to monitor for pseudoaneurysm formation or aneurysmal degeneration of the false lumen Ullah 2019.

49.7Areas of controversy

The causative mechanism of median arcuate ligament syndrome remains debated, with persistent uncertainty regarding the relative contributions of ischemic flow reduction versus celiac plexus neurogenic pain AOB Consensus 2026. Comparative outcomes between open and endovascular CMI revascularization are confounded by significant selection bias, complicating robust cost-effectiveness analyses Patel 2023 · Wolk 2022. Duplex velocity thresholds for in-stent restenosis are center-specific and lack uniformly established criteria Yu 2022. The optimal agent and duration for antithrombotic therapy in isolated visceral artery dissection remain heterogeneous across protocols Ullah 2019. The clinical implications and timing of recovery for CMI-associated intestinal dysbiosis following revascularization remain uncertain Munley 2023.