Mesenteric Vascular Disease

MVD: Intro & Anatomy - Gut Feeling Gone Wrong

• Mesenteric Vascular Disease (MVD): Insufficient blood supply to intestines.
• Key Types:
  • Acute Mesenteric Ischemia (AMI): Sudden arterial blockage.
  • Chronic Mesenteric Ischemia (CMI): Gradual narrowing; "intestinal angina".
  • Mesenteric Venous Thrombosis (MVT): Venous outflow obstruction.
• Primary Arteries:
  • Celiac Trunk: Supplies foregut (e.g., stomach, duodenum).
  • Superior Mesenteric Artery (SMA): Supplies midgut (e.g., jejunum, ileum, right colon).
  • Inferior Mesenteric Artery (IMA): Supplies hindgut (e.g., left colon, rectum).
• Critical Collaterals:
  • Marginal Artery of Drummond: Connects SMA & IMA branches.
  • Arc of Riolan (Meandering Mesenteric Artery): Direct SMA-IMA link.

⭐ Superior Mesenteric Artery (SMA) is the most commonly affected vessel in acute mesenteric ischemia.

Acute Mesenteric Ischemia - Time Is Bowel

Life-threatening emergency; rapid diagnosis & intervention crucial. "Time is bowel." High mortality (~70-90% if delayed).

• Types & Causes:
  • Arterial Embolic (~50%): Cardiac source (AF, MI).
  • Arterial Thrombotic (~25%): Atherosclerosis (often prior CMI).
  • Non-Occlusive (NOMI, ~20%): Low flow states (shock, vasopressors).
  • Mesenteric Venous Thrombosis (MVT, ~5%): Hypercoagulability, malignancy. 📌 Hypercoagulable, Inflammation, Malignancy, Portal HTN (HIMP).
• Clinical:

  ⭐ Classic: Severe abdominal pain 'out of proportion' to physical findings.

  • N/V/D, bloody stools (late). Peritoneal signs = infarction.
• Diagnosis:
  • Labs: ↑ Lactate (> 2 mmol/L), acidosis (pH < 7.35), ↑ D-dimer.
  • Imaging: CTA (gold standard).
• Management Algorithm:

Chronic Mesenteric Ischemia - Slow Gut Starvation

• Pathophysiology: Atherosclerosis (most common, >90%) leading to ↓ blood flow, typically requiring >70% stenosis in ≥2 major mesenteric arteries (celiac, SMA, IMA).
• Clinical Presentation:
  • Often insidious onset.
  • ⭐ > Triad: Postprandial abdominal pain ("intestinal angina", ~30 min after meals, dull/crampy), significant weight loss (due to malabsorption & food fear), and food fear (sitophobia).
  • Abdominal bruit may be present (~50%).
• Diagnosis:
  • Duplex ultrasound (screening).
  • CTA or MRA (confirmatory, preferred).
  • Conventional angiography (gold standard, allows intervention).
• Management: Revascularization (angioplasty/stenting or surgical bypass) is key. Nutritional support vital. 📌 Mnemonic: "Angina (intestinal), Weight loss, Food fear" (AWFul gut pain).

Related MVD Conditions - Vascular Villains

• Ischemic Colitis (IC)
  • Most common mesenteric ischemia; typically non-occlusive (low flow).
  • Key sites: Watershed areas (splenic flexure, rectosigmoid junction).
  • Clinical: Sudden cramping LLQ pain, hematochezia, tenesmus.
  • Imaging: "Thumbprinting" (submucosal edema/hemorrhage) on CT/barium.

  ⭐ Ischemic colitis most commonly affects watershed areas like the splenic flexure and rectosigmoid junction.

• Median Arcuate Ligament Syndrome (MALS)
  • Celiac artery compression by the median arcuate ligament of diaphragm.
  • Classic: Postprandial epigastric pain, weight loss, epigastric bruit (louder on expiration).
  • Diagnosis: Duplex US (↑ celiac velocity with expiration), CT/MR angiography (focal stenosis, hooked appearance).
• Segmental Arterial Mediolysis (SAM)
  • Rare non-atherosclerotic, non-inflammatory vasculopathy; causes dissection/aneurysm.
  • Primarily affects splanchnic arteries (splenic, hepatic, SMA).
  • Pathology: Lysis of outer arterial media → weakness.
  • Presentation: Acute severe abdominal pain, intra-abdominal hemorrhage, shock; often younger patients.

High‑Yield Points - ⚡ Biggest Takeaways

• Acute Mesenteric Ischemia (AMI): Severe pain "out of proportion" to findings; SMA embolism (AFib) is most common.
• Chronic Mesenteric Ischemia (CMI): "Intestinal angina" (postprandial pain, weight loss, food fear) from atherosclerosis.
• Diagnosis: CT Angiography (CTA) is gold standard. ↑ lactate is a late, poor prognostic sign in AMI.
• AMI Treatment: Urgent revascularization (surgical/endovascular) ± bowel resection.
• Mesenteric Venous Thrombosis (MVT): Linked to hypercoagulable states; primary treatment is anticoagulation.
• Non-Occlusive Mesenteric Ischemia (NOMI): Due to low flow/vasoconstriction; treat cause, consider vasodilators.