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MESENTERIC ISCHEMIA

Mesenteric Ischemia

Types of Acute Mesenteric Ischemia (MI):

  1. Acute Mesenteric Embolism
  2. Acute Mesenteric Thrombosis
  3. Acute Venous Thrombosis (VT)
  4. Non-Occlusive Mesenteric Ischemia (NOMI)

Chronic Mesenteric Ischemia (CMI):

  • Characterized by food fear due to postprandial abdominal pain.

Other Causes of Mesenteric Ischemia:

  • Dissection
  • Malignancy
  • Vasculitis
  • Radiation

Key Symptoms:

  • Pain out of proportion: Classical finding in mesenteric ischemia.
  • Food fear: Typical in chronic mesenteric ischemia (CMI).

Mesenteric Vasculature & Collateral Circulation:

  • Collateral Circulation:
    • Best: Stomach, duodenum, rectum.
    • Least: Splenic flexure of the colon, sigmoid colon.
  • Between Celiac Axis and SMA:
    • Superior and inferior pancreaticoduodenal arteries form collateral circulation.
  • Collaterals Between SMA & IMA:
    • Marginal artery of Drummond:
      • Close to the colonic wall.

    • Meandering mesenteric artery of Moskowitz:

      • Larger and more centrally placed.

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Acute Mesenteric Ischemia (AMI)

1. Arterial Embolism

  • Most common source: Cardiac (e.g., mitral stenosis (MS), atrial fibrillation (AF)).
  • Second most common cause of AMI.
  • Most common site: Superior mesenteric artery (SMA) due to its acute origin and high flow.
  • Demographics: More common in females than males.
  • Emboli location:
    • 50% lodge distal to the origin of the middle colic artery.
    • Affects jejunum, ileum, and ascending colon.
    • Rare involvement of duodenum and proximal jejunum.
    • 15% lodge at the origin of the SMA.
  • Symptoms:
    • Pain out of proportion to clinical findings.
    • Peritonitis signs in advanced stages.
    • Leukocytosis: Most common early finding.
    • Late signs: Increased lactate and acidosis.

Diagnostic Tests

  • Gold standard: Conventional angiography.
  • Investigation of choice: CT angiography.

Treatment

  1. Surgery:
    • Single vessel embolectomy.
    • Bowel resection if gangrenous or perforated.
  2. Catheter-based thrombolytic therapy:
    • For unstable patients.

2. Arterial Thrombosis

  • Common locations:
    • In areas of arteriosclerotic narrowing, typically at the proximal origin of major mesenteric vessels.
  • Involves more branches, making it more devastating.
  • Affects the duodenum and proximal jejunum.
  • Pulselessness over the entire SMA region is common.

Treatment

  1. Bypass surgery:
    • Using autologous or prosthetic grafts.
    • Autologous grafts preferred if full-thickness ischemia or bowel contamination is present.
  2. Stenting:
    • Poor long-term effect but better short-term results.

3. Non-Occlusive Mesenteric Ischemia (NOMI)

Key Diagnostic Tools:

  • CT Angiography (CTA): Highly useful for diagnosis.
  • Conventional Angiography:
    • Has the highest sensitivity for detecting NOMI.

Therapeutic Management:

  • Maximizing Cardiac Output: Critical for ensuring adequate mesenteric perfusion.
  • Appropriate Resuscitation: Fluid resuscitation to restore and maintain hemodynamic stability.
  • Anticoagulation: To prevent further ischemic events.
  • Discontinuation of Potentiating Medications: Medications contributing to reduced mesenteric blood flow should be stopped.

Interventional Treatment:

  • Direct SMA Papaverine:
    • Papaverine can be directly infused into the SMA to induce vasodilation and improve blood flow.

4. Mesenteric Vein Thrombosis (MVT)

Key Features:

  • Accounts for ~15% of all Acute Mesenteric Ischemia (AMI) cases.
  • Lower mortality compared to arterial ischemia.
  • Superior Mesenteric Vein (SMV) is the most commonly involved vessel.
  • May extend to the Portal vein.

Clinical Findings:

  • Common in younger patients.
  • Hemorrhagic ascites may be present.
  • Different clinical presentation compared to arterial ischemia.

Risk Factors:

  • Protein C and Protein S deficiencies.
  • Antithrombin III deficiency.
  • Factor V Leiden mutation.
  • History of DVT in 20-40% of cases.

Diagnosis:

  • CECT with venous phase is the best diagnostic tool.

Management:

  • Anticoagulation: Most important intervention.
  • Surgery and clearance of thrombus are not indicated in all patients.

Mortality:

  • General mortality rate: 25-30%.
  • If bowel resection is required, mortality increases to ~50%.
  • Most common cause of death: Sepsis and MODS (Multiple Organ Dysfunction Syndrome).

Duration of Anticoagulation:

  • Life-long: For inherited deficiencies.
  • Long-term: For idiopathic cases.
  • 3-6 months: For inflammatory causes.

Chronic Mesenteric Ischemia (CMI)

Key Features:

  • Chronic hypoperfusion of the small bowel.
  • Occurs when two or more major mesenteric vessels are stenosed.
  • Most patients are asymptomatic.
  • Most common cause: Ostial atherosclerotic disease.
  • Male to female ratio: 1:4.
  • Classic triad: Postprandial pain, food fear, and significant weight loss (pathognomonic for CMI).

Diagnostic Investigations:

  • Investigation of choice: CT Angiography.
  • Duplex Scan Criteria:
    1. Wisconsin Criteria:
      • Peak systolic velocity:

        • 200 cm/s in Celiac Artery (CA).

        • 275 cm/s in Superior Mesenteric Artery (SMA)

          • indicating > 70% stenosis.
    2. Dartmouth Criteria:
      • End-diastolic velocity:

        • 55 cm/s in CA.

        • 45 cm/s in SMA

          • indicating > 50% stenosis.

Treatment Options for CMI:

Bypass Surgery:

  1. Antegrade Bypass:
    • Bifurcated aortoceliac and aorto-SMA bypass.
  2. Retrograde Bypass:
    • Infrarenal aorta-SMA bypass.
  3. Graft Patency:
    • 80-100% for 1-3 years.
  4. Operative mortality: Less than 2%.
  5. Duplex USG:
    • Routine graft imaging every 6 months for the first year, then annually.

Endarterectomy:

  • Indications:
    1. Gross contamination of the abdominal cavity.
    2. Autologous conduit unavailable.
    3. Coral reef type clots.
    4. Diseased supraceliac and infrarenal aorta.

Endovascular Therapy:

  • Aim: Reduce stenosis to less than 50% of luminal diameter.
  • Provides immediate symptomatic relief in 75-100% of patients.
  • Primary stenting recommended.
  • Covered stents are preferred.
  • Most preferred approach: Femoral.
  • Other approaches: Left brachial and axillary.

MCQs for Revision

1. Investigation of choice for acute mesenteric ischemia is:

A) CT angiography

B) MRI

C) DSA

D) CECT abdomen

Correct Answer: A) CT angiography

2. Sitophobia is seen in:

A) Acute mesenteric ischemia

B) Zenker's diverticulum

C) Chronic mesenteric ischemia

D) Duodenal diverticula

Correct Answer: C) Chronic mesenteric ischemia

(Sitophobia refers to "food fear" due to postprandial pain in chronic mesenteric ischemia.)

3. The most common cause of acute mesenteric ischemia is:

A) Arterial embolism

B) Arterial thrombosis

C) Venous thrombosis

D) Trauma

Correct Answer: A) Arterial embolism

4. All are true regarding NOMI except:

A) Common in critically ill patients

B) Early diagnosis helps improve outcomes

C) Most useful studies are CTA and conventional diagnostic angiography

D) CTA has the highest sensitivity

Correct Answer: D) CTA has the highest sensitivity

(Conventional angiography has the highest sensitivity in diagnosing NOMI.)

5. A 60-year-old man was taken up for laparotomy for severe abdominal pain. Intraoperatively, the distal duodenum and proximal jejunum were gangrenous. The most probable cause is:

A) AMI due to arterial emboli

B) AMI due to arterial thrombus

C) Mesenteric vein thrombosis

D) Chronic mesenteric ischemia

Correct Answer: B) AMI due to arterial thrombus

(Involvement of the duodenum and proximal jejunum suggests arterial thrombosis.)

6. Which of the following is not true regarding Wisconsin criteria used in the assessment of mesenteric ischemia?

A) Based on peak systolic velocity

B) Flow velocity >200 cm/s in CA indicates >70% stenosis

C) Flow velocity >275 cm/s in SMA indicates >70% stenosis

D) Based on end-diastolic velocity

Correct Answer: D) Based on end-diastolic velocity

(Wisconsin criteria are based on peak systolic velocity.)

7. All of the following are indications for endarterectomy in the treatment of CMI except:

A) No contamination of the abdominal cavity

B) Autologous conduit not available

C) Coral reef clots

D) Diseased supraceliac & infrarenal aorta

Correct Answer: A) No contamination of the abdominal cavity

(Endarterectomy is performed in cases of gross contamination, not when there is no contamination.)

8. The most constant branch of the Superior Mesenteric Artery is:

A) Inferior pancreaticoduodenal artery

B) Right colic artery

C) Middle colic artery

D) Ileo-colic artery

Correct Answer: D) Ileo-colic artery

9. Question: In which condition is this sign seen?

image.png

A) Acute mesenteric ischemia

B) NOMI

C) Vasculitis

D) Chronic mesenteric ischemia

Explanation:

The sign shown in the image is characteristic of Non-Occlusive Mesenteric Ischemia (NOMI). The image likely depicts a spasm of the mesenteric arteries, which is typical in NOMI. In this condition, there is vasoconstriction of mesenteric vessels without an occlusive thrombus or embolus. NOMI is frequently seen in critically ill patients and can be confirmed using diagnostic angiography, which shows mesenteric vasospasm and narrowing of arteries.

Correct Answer:

B) NOMI