Chronic mesenteric ischemia (CMI) — also called intestinal angina — is caused by stenosis or occlusion of the mesenteric arteries. It's underdiagnosed because symptoms are vague: postprandial pain, food fear, and weight loss. Mesenteric artery duplex is the primary non-invasive test. Here's how to approach it.

Clinical Context

The bowel has a rich collateral supply from three vessels:

Celiac axis (CA): Supplies the foregut (stomach, liver, spleen, pancreas)
Superior mesenteric artery (SMA): Supplies the midgut (small bowel, right colon)
Inferior mesenteric artery (IMA): Supplies the hindgut (left colon, sigmoid, rectum)

Single-vessel stenosis rarely causes symptoms because of collateral flow. Significant CMI typically requires disease in two or more vessels. The celiac and SMA are the vessels most commonly assessed by duplex.

Indications

Chronic postprandial abdominal pain (pain 15–30 minutes after eating, lasting 1–2 hours)
Unexplained weight loss with bowel symptoms
Food fear (sitophobia — avoiding eating to prevent pain)
Suspected celiac artery compression syndrome (median arcuate ligament syndrome)
Evaluation before mesenteric revascularization
Post-procedure surveillance

Equipment and Setup

Probe: 2–5 MHz curvilinear. Bowel gas is the enemy — a curved probe gets under the ribs better than a linear.

Patient prep: Fasting 8–12 hours is critical. A full bowel is impossible to scan through. Fasting also allows you to assess normal fasting velocities as a baseline.

Patient position: Supine. Elevating the head of the bed slightly can help in obese patients.

Tip: These exams often take 60–90 minutes for complete evaluation. Warn the patient.

Anatomy

Celiac axis:

First major branch of the aorta below the diaphragm, at T12/L1
Short trunk (1–2 cm), trifurcates (or bifurcates) into the common hepatic artery, splenic artery, and left gastric artery
The celiac has a low-resistance waveform (supplies highly vascular organs)

Superior mesenteric artery:

Arises from the aorta 1–2 cm below the celiac, at L1
Courses inferiorly behind the pancreatic neck, then over the third portion of the duodenum
Fasting: High resistance (reduced bowel activity) — prominent reversal of diastolic flow is normal
Post-prandial: Low resistance — forward diastolic flow increases significantly

Scanning Technique

Step 1: Aorta Survey

Start with the proximal aorta in sagittal — identify the celiac and SMA origins. Note the aortic diameter (aneurysmal disease may coexist) and proximal aortic Doppler waveform (you'll use the aortic PSV for ratio calculations).

Step 2: Celiac Axis

Sagittal or transverse approach at the epigastrium
Short vessel — find its origin from the aorta, then follow to its bifurcation/trifurcation
Sample at: origin (1 cm from aorta), mid vessel, and at the bifurcation
Celiac has a characteristic "seagull" or "T" shape in transverse as it divides

Technique for celiac: In transverse, the celiac looks like a seagull in flight — the two wings are the splenic (left) and hepatic (right) arteries, the body is the celiac trunk. This is your landmark.

Step 3: Superior Mesenteric Artery

Sagittal plane: the SMA runs parallel to the aorta, separated by the renal vein and splenic vein
Sample at: origin (1 cm from aorta), proximal, and mid SMA
Keep Doppler angle ≤ 60°

Normal fasting SMA waveform: Triphasic with reversal of diastolic flow — high resistance, similar to peripheral arteries. This is NORMAL in a fasting patient.

Diagnostic Criteria

Celiac Axis

Stenosis	PSV
Normal	< 200 cm/s
≥ 70% stenosis	> 200 cm/s
Occlusion	Absent flow, post-stenotic turbulence in hepatic/splenic

Superior Mesenteric Artery

Stenosis	Fasting PSV
Normal	< 275 cm/s
≥ 70% stenosis	> 275 cm/s
Occlusion	Absent flow

Celiac-to-aortic ratio and SMA-to-aortic ratio may also be used (PSV at stenosis ÷ PSV at aorta) similarly to renal artery RAR. Values > 3.5 suggest significant stenosis.

Median Arcuate Ligament Syndrome (MALS)

MALS occurs when the median arcuate ligament of the diaphragm compresses the celiac axis from above, typically in young, thin patients.

Ultrasound findings:

Elevated celiac PSV on inspiration that normalizes or decreases on expiration
The hook-shaped compression of the celiac origin visible on B-mode
Post-stenotic turbulence

Key technique: Obtain celiac Doppler in both deep inspiration (increases compression) and full expiration (releases compression). A PSV that drops significantly from inspiration to expiration — or that exceeds 200 cm/s on inspiration but normalizes on expiration — is characteristic of MALS.

Post-Prandial Evaluation (Optional)

If fasting velocities are normal but clinical suspicion is high, a post-prandial study can be performed. The patient eats a standardized meal (or glucose drink), and the SMA is rescanned at 30 minutes.

Normal post-prandial response: SMA PSV increases and EDV increases significantly (diastolic flow increases, RI drops). A blunted response suggests hemodynamically significant disease.

What to Document

Aortic PSV (reference for ratios)
Celiac: origin PSV, visualization quality, presence of turbulence
SMA: origin PSV, proximal PSV, waveform character (fasting)
Note whether any vessels were not visualized (bowel gas)
Respiratory variation for celiac if MALS suspected

Reporting Language

"Celiac axis PSV 148 cm/s, SMA PSV 186 cm/s. Normal fasting waveforms. No hemodynamically significant stenosis of the celiac axis or SMA."
"Celiac axis PSV elevated at 310 cm/s with post-stenotic turbulence at the origin. Celiac-to-aortic ratio 4.1. SMA PSV 205 cm/s. Findings consistent with hemodynamically significant celiac axis stenosis and possible SMA stenosis."
"Celiac axis PSV 390 cm/s on deep inspiration, decreasing to 110 cm/s on full expiration. Consistent with extrinsic celiac axis compression — findings suggest median arcuate ligament syndrome (MALS)."

SonoBuddy's vascular protocols include mesenteric artery duplex criteria and normal value ranges in the Measurements section.

Mesenteric Artery Duplex: Scanning the SMA and Celiac for Bowel Ischemia