Vascular: Mesenteric Ischemia

Mesenteric Stenosis/Ischemia

Basics

  • Visceral Perfusion Fails to Meet Organ Metabolic Requirements
  • More Common in Women (3:1)
  • Can Be Complicated by Bowel Necrosis
    • Mucosa is Affected First Due to Higher Metabolic Demand

Types

  • Acute Mesenteric Ischemia (AMI) – Rapid Over Hours-Days
    • Most Common Cause: Arterial Emboli
  • Chronic Mesenteric Ischemia (CMI) – Slow Over Weeks-Months
    • Most Common Cause: Atherosclerosis

Necrotic Bowel from Mesenteric Ischemia 1

Acute Mesenteric Ischemia

Causes

  • Arterial Disease
    • Arterial Embolism
      • Most Common Cause of Acute Mesenteric Ischemia (40-50%)
      • Most Common Source: Heart
      • Most Common Site: SMA Just Distal to Middle Colic Artery
        • Anatomy:
          • SMA Has a Decreased Angle of Takeoff Compared to Other Mesenteric Vessels
          • SMA Begins to Narrow After Middle Colic Takeoff
        • Spares Proximal Jejunum & Transverse Colon
    • Arterial Thrombosis
      • Second Most Common Cause of Acute Mesenteric Ischemia (20-35%)
      • May Have History of Chronic Mesenteric Ischemia & “Food-Fear”
      • Most Common Site: SMA Origin
        • Involves Entire Distribution
      • Higher Mortality Than Arterial Embolism
  • Mesenteric Venous Thrombosis
    • Classification:
      • Primary – Idiopathic
      • Secondary – From Underlying Process
        • More Common (90%)
        • Causes: Injury, Venous Stasis or Thrombophilia
    • Often Vague & Less Dramatic
  • Non-Occlusive Mesenteric Ischemia (NOMI)
    • Ischemia Without Associated Thromboembolic Occlusion
    • Causes:
      • Decreased Perfusion from Low Cardiac Output (Most Common)
        • Systemic Vasopressors & Hemodialysis Increase Risk
      • Hypovolemia
      • Cocaine-Induced Vasoconstriction
    • Most Vulnerable Sites: Watershed Areas
    • Often More Insidious Onset than Arterial Disease
    • Highest Mortality Rate – Association with Multi-Organ Failure

Presentation

  • Abdominal Pain – Most Common Symptom
    • Sudden & Severe
    • “Pain Out of Proportion” – Patient Reports Significant Abdominal Pain That Does Not Correlate to Physical Exam Findings with Only Mild Abdominal Tenderness
  • Bloody Diarrhea (Sudden & Forceful)
  • Nausea & Vomiting
  • Abdominal Distention
  • Fever

Diagnosis

  • Dx: CTA
  • Mesenteric Duplex US Poor in Acute Setting – Obscured by Bowel Gas & More Operator Dependent

Initial Managements

  • Aggressive Fluid Resuscitation
  • Aggressive Electrolyte Correction
  • Heparin (Not Necessary for NOMI)
  • Broad-Spectrum ABX (High Risk for Bacterial Translocation)
  • If Unstable or Peritonitis: Exploratory Laparotomy & Resection of Necrotic Bowel
    • Resect Areas of Complete Ischemia Before Embolectomy or Revascularization (Risk of Infection)
    • Reevaluate Areas of Partial Ischemia After Embolectomy or Revascularization
    • Low Threshold for Open Abdomen & Second Look if Bowel Viability is Questioned

Definitive Treatment

  • Arterial Embolus: Open SMA Embolectomy
    • Uses a Proximal Transverse Arteriotomy
    • Balloon Catheter Inserted Proximally & Distally to Extract Embolus
    • May Consider Endovascular Embolectomy in Select Stable & Nonperitoneal Patients
  • Arterial Thrombosis: Open SMA Bypass
    • Bypass Route:
      • Right Common Iliac Artery to SMA – Preferred Route
        • Retrograde in “Lazy-C” Configuration
      • Left Common Iliac Artery
      • Infrarenal Aorta – Higher Risk of Kinking Given Shorter Graft
      • Antegrade Supraceliac Bypass – More Difficult Dissection
        • Only If Diseased Infrarenal Aorta & Iliacs
    • Graft Options:
      • Synthetic Graft – Preferred
        • Better Patency, Size Match, Easier Handling & Kink Resistant
      • Autogenous Vein
        • Preferred if Bowel Necrosed or with Peritoneal Spillage
    • If Both Celiac & SMA Diseased: Use Bifurcated Prosthetic Conduit to Both
  • Mesenteric Venous Thrombosis: Heparin & Lifelong Anticoagulation
  • Non-Occlusive Mesenteric Ischemia (NOMI): Improve Circulatory Support & Catheter-Directed Intra-Arterial Vasodilators to SMA
    • Vasodilators: Nitro, Papaverine or Prostaglandin E1 (PGE1)

Endovascular Treatment

  • Generally Avoided in Acute Mesenteric Ischemia Due to Concern for Bowel Ischemia Requiring Surgical Evaluation
  • May Consider if Poor Surgical Candidate & No Sign of Bowel Necrosis

Mesenteric Ischemia with Embolism on CTA 2

Mesenteric Ischemia from SMA Stenosis on CTA 3

Mesenteric Venous Thrombosis on CTA – SMV Thrombus (Blue Arrows), Intact SMA (Red Arrows), Edematous Jejunum (White Arrows) 4

NOMI with Ischemia at Griffith’s Point 5

SMA Bypass with C-Loop Graft 6

Chronic Mesenteric Ischemia

Basics

  • Most Common Cause: Atherosclerosis
  • Risk Factors:
    • Smoking
    • Hypertension
    • Hyperlipidemia
  • More Common in Elderly Cachectic Females
  • Due to Rich Collateral System Symptoms Typically Only Develop Once ≥ 2 Vessels (Celiac/SMA/IMA) are Significantly Stenosed

Presentation

  • Postprandial Abdominal Pain (Intestinal Angina)
  • Pain Causes “Food Fear” & Weight Loss/Malnutrition

Diagnosis

  • Screening: Mesenteric Duplex US
    • Assess Celiac & SMA; IMA Difficult to Visualize
    • Peak Systolic Velocity (PSV) Defining Values Not Clearly Defined
    • Moneta Criteria Indicating ≥ 70% Stenosis:
      • SMA PSV ≥ 275 cm/s
      • Celiac PSV ≥ 200 cm/s
  • Dx: CTA or MRA
    • Gold-Standard: Angiography – More Often Used for Planned Treatment than for Diagnostics

Treatment

  • Indications for Revascularization:
    • All Symptomatic Patients Should Be Treated
    • Asymptomatic Severe 3-Vessel Disease
  • Primary Tx: Endovascular Balloon Angioplasty & Stenting
    • If Anatomy Unfavorable: Consider Open Revascularization/Bypass
  • Often Require Preoperative Nutrition Optimization

References

  1. Zachariah SK. Adult necrotizing enterocolitis and non occlusive mesenteric ischemia. J Emerg Trauma Shock. 2011 Jul;4(3):430-2.(License: CC BY-NC-SA-3.0)
  2. Clores MJ, Monzur F, Rajapakse R. Acute Mesenteric Ischemia Caused by Rare Cardiac Tumor Embolus. ACG Case Rep J. 2014 Oct 10;2(1):27-9. (License: CC BY-NC-ND-4.0)
  3. Reginelli A, Genovese E, Cappabianca S, Iacobellis F, Berritto D, Fonio P, Coppolino F, Grassi R. Intestinal Ischemia: US-CT findings correlations. Crit Ultrasound J. 2013 Jul 15;5 Suppl 1(Suppl 1):S7. (License: CC BY-2.0)
  4. Kim HM, Kim HL, Lee HS, Jung JH, Kim CH, Oh S, Kim JH, Zo JH. Nonbacterial Thrombotic Endocarditis in a Patient with Bowel Infarction due to Mesenteric Vein Thrombosis. Korean Circ J. 2014 May;44(3):189-92. (License: CC BY-NC-3.0)
  5. Baugh CW, Levine AC, Pallin DJ. Heart block and nonocclusive mesenteric ischemia. Int J Emerg Med. 2009 Sep;2(3):171-2. (License: CC BY-NC-2.0)
  6. Jun HJ. Isolated bypass to the superior mesenteric artery for chronic mesenteric ischemia. Korean J Thorac Cardiovasc Surg. 2013 Apr;46(2):146-9. (License: CC BY-NC-3.0)