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Mesenteric Ischemia

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Mesenteric Ischemia, Acute Mesenteric Ischemia, Mesenteric Infarction, Colonic Ischemia, Intestinal Ischemia, Colonic Vasculitis, Ischemic Colitis, Visceral Artery Ischemia, Acute Intestinal Vascular Insufficiency, Acute Ischemic Enteritis

  • Anatomy
  1. Mesenteric Arteries
    1. Celiac Artery
      1. Foregut (proximal duodenum and Stomach)
      2. Hepatobiliary system
      3. Spleen
    2. Superior Mesenteric Artery
      1. Midgut (Small Intestine and proximal colon to splenic flexure)
    3. Inferior Mesenteric Artery
      1. Hindgut (descending colon, sigmoid colon and Rectum)
  2. Mesenteric Veins
    1. Parallels arterial supply for the most part
    2. Superior Mesenteric Vein
      1. Drains the Small Intestine and proximal colon
    3. Inferior Mesenteric Vein
      1. Drains the hindgut
  • Pathophysiology
  1. Timing
    1. Mesenteric hypoperfusion
      1. Collateral circulation can compensate for 75% reduced flow for up to 12 hours before major injury
    2. Reversible Mesenteric Ischemia
      1. Mucosal Villi necrosis starts within 3-4 hours from onset of ischemia
    3. Transmural injury (bowel necrosis and perforation)
      1. Onset within 6 hours of ischemia onset
      2. Intestinal wall may appear edematous
    4. Bowel Hemorrhage, Gangrene and Perforation
      1. Onset within 1-4 days after Mesenteric Ischemia without intervention
      2. Intestinal wall appears edematous, friable and hemorrhagic
  2. Watershed blood supply areas most often affected
    1. Splenic flexure (intersection of SMA and IMA distribution)
    2. Rectosigmoid
  • Epidemiology
  1. Uncommon condition (but requires high index suspicion)
    1. Accounts for 0.1 to 1% of Acute Abdominal Pain admissions, but has a mortality of 24-94%
    2. Rapid diagnosis is critical to survival
  2. More common in elderly
  3. More common in women
  • Risk Factors
  1. Atherosclerosis
  2. Atrial fiibrillation
  3. Dilated Cardiomyopathy
  4. Valvular Disease
  5. Advanced age
  6. Intra-Abdominal Cancer
  7. Rapid weight loss (e.g. Anorexia)
    1. Results in decreased fat between duodenum and superior Mesenteric Artery
    2. Ischemia results from duodenal compression of the superior Mesenteric Artery
  8. Critical Illness, Major Surgery or Strenuous Exercise (hypoperfusion outlasts initial insult)
    1. Myocardial Infarction (recent)
    2. Hypovolemia
  • Causes
  • Primary Acute Mesenteric Ischemia (intravascular)
  1. Mesenteric Artery Embolism (50%)
    1. Superior Mesenteric Artery Embolism is affected in most cases
      1. More than half lodge distal to the middle colic artery origin (6-8 cm from SMA origin)
  2. Mesenteric Artery Thrombosis (15-25%)
    1. Superior Mesenteric Artery Thrombosis
  3. Nonocclusive Mesenteric Ischemia - NOMI (20-30%)
    1. Results from Low Cardiac Output (shock) and mesenteric arterial Vasoconstriction (severe and prolonged)
    2. Causes include Septic Shock, Cardiogenic Shock, Hypovolemic Shock and Bowel Obstruction with Strangulation
  4. Mesenteric Venous Thrombosis - MVT (5-10%)
    1. Hypercoagulable State
    2. Typically with underlying diffuse atherosclerosis and Chronic Mesenteric Ischemia
  1. See Chronic Mesenteric Ischemia
  2. Diffuse atherosclerotic disease in 95% of cases
    1. All major mesenteric vessels (SMA, IMA, Celiac Artery) with stenosis or Occlusion
  • Causes
  • Secondary Mesenteric Ischemia (compression)
  1. Adhesions
  2. Herniation
  3. Volvulus
  4. Intussusception
  5. Tumor
  6. Trauma
  7. Retroperitoneal fibrosis
  • Precautions
  1. Have a low index of suspicion in Abdominal Pain out of proportion in older patients or Atrial Fibrillation
  • Symptoms
  1. Abdominal Pain
    1. Severe, colicky or cramping pain, and out of proportion to exam
    2. Pain is poorly localized
    3. Left Lower Quadrant abdominal cramping may occur in Mesenteric Artery Embolism or thrombosis
    4. Epigastric or Periumbilical Pain may occur in Chronic Mesenteric Ischemia
  2. Timing
    1. Sudden onset, severe abrupt Abdominal Pain out of proportion to exam
      1. Mesenteric Artery Embolism
      2. Mesenteric Venous Thrombosis
    2. Gradual onset of less severe Abdominal Pain (due to incomplete Occlusion, collaterals)
      1. Mesenteric Artery Thrombosis
      2. Nonocclusive Mesenteric Ischemia (NOMI)
    3. Progressive postprandial pain
            1. Chronic Mesenteric Ischemia
  3. Gastroenteritis-type symptoms (one third of cases)
    1. Diarrhea progressing to Constipation
      1. Superior Mesenteric Artery Embolism
      2. Superior Mesenteric Artery Thrombosis
    2. Nausea and Vomiting
      1. Superior Mesenteric Artery Embolism
      2. Mesenteric Venous Thrombosis
      3. Chronic Mesenteric Ischemia
  4. Chronic Malnutrition, Cachexia or Wasting Syndrome
    1. Chronic Mesenteric Ischemia (Abdominal Angina)
  • Signs
  1. Abdominal exam may be benign early in course
  2. Peritonitis and systemic features in delayed presentation (1-3 days after onset)
    1. Abdominal tenderness to palpation
    2. Fever
    3. Fecal Occult Blood positive in 25% of cases
  • Labs
  • Diagnosis
  1. Complete Blood Count (CBC)
    1. Leukocytosis >15,000 with Left Shift is common
  2. Serum Phosphate Level
    1. Increases within 4 hours (75%)
  3. Labs abnormal if prolonged bowel ischemia, infarction, necrosis or perforation occurs
    1. Arterial Blood Gas (ABG) with Metabolic Acidosis
    2. Serum Amylase increased
    3. Serum lactate increased
  4. Malnutrition Labs in Chronic Mesenteric Ischemia
    1. Anemia
    2. Leukopenia or Lymphopenia
    3. Hypoalbuminemia
  • Labs
  • Other
  1. Basic metabolic panel (e.g. Chem8)
    1. Electrolytes
    2. Renal Function tests
      1. Blood Urea Nitrogen (BUN)
      2. Serum Creatinine
  2. Liver Function Tests (LFT)
    1. AST increased
    2. Lactate Dehydrogenase (LDH)
    3. Creatine Phosphokinase (CK-MM) Increased
  3. Sepsis and Ischemia related labs
    1. Lactic Acid (marker of bower ischemia or infarction)
      1. Normal Lactic Acid dose not exclude Mesenteric Ischemia
    2. Blood Cultures
    3. Urinalysis and Urine Culture
  4. Coagulation Studies
    1. ProTime (INR)
    2. Partial Thromboplastin Time (PTT)
    3. Consider Hypercoagulable lab studies in Mesenteric Venous Thrombosis
  5. Miscellaneous
    1. Type and Cross Match Blood
  • Imaging
  • Advanced (Preferred)
  1. CT Abdomen Pelvis and CT Angiography
    1. First-line study in most cases
    2. Efficacy
      1. Test Sensitivity: 71-96%
      2. Test Specificity: 92-94%
    3. Progression of bowel changes in Mesenteric Ischemia
      1. Mesenteric Edema and streaking
      2. Bowel wall thickening (edema, Hemorrhage)
      3. Bowel wall gas (pneumotosis intestinalis) and Portal Vein gas in necrosis
    4. Findings in Mesenteric Venous Thrombosis
      1. Mesenteric vein or Portal Vein engorgement
      2. Visceral edema
    5. Findings in Mesenteric Occlusion
      1. Mesenteric Artery Thrombosis will demonstrate proximal stenosis or Occlusion of SMA, IMA or Celiac Artery
      2. Mesenteric Artery Embolism related Occlusion site is more difficult to identify on CT
  2. Angiography (gold standard)
    1. Largely replaced by CT, but indicated in unclear cases (e.g. embolus)
    2. Also indicated for intervention
    3. Best defines Occlusion and stenosis sites
      1. Anteroposterior Views (collateral pathways)
      2. Lateral Views (visceral branches)
  3. Contrast-Enhanced MRA Abdomen
    1. Contrast-Enhanced MRA is the best modality to fully evaluate for abdominal vascular disease
    2. Limited use in the acute setting, but ideal imaging for Chronic Mesenteric Ischemia
  4. Mesenteric Duplex Ultrasound
    1. Evaluates only proximal, main vessels (SMA, IMA and Celiac Artery)
    2. Test Sensitivity: 70-89%
    3. Test Specificity: 92-100%
    4. Ultrasound is useful in combination with angiography following visceral bypass graft or endovascular stenting
    5. Limited Test Sensitivity due to overlying bowel gas that may interfere with study
  • Imaging
  • Abdominal XRay (KUB)
  1. Advanced imaging (see above) is always preferred when available
  2. XRay is listed for historical purposes and in low resource centers
  3. Findings suggestive of Mesenteric Ischemia (20-60%)
    1. Adynamic Ileus
    2. Thumb printing of bowel wall
    3. Bowel wall thickening
    4. Air in bowel wall or Portal Vein
  4. Other conditions identified
    1. Small Bowel Obstruction
      1. Air-fluid levels
      2. Fixed dilated loops of bowel
    2. Volvulus
    3. Viscus perforation
  • Management
  1. Immediate Surgical Consultation
  2. Beyond general supportive care, management differs depending on cause
    1. Mesenteric Artery Embolism
    2. Mesenteric Artery Thrombosis
    3. Nonocclusive Mesenteric Ischemia (NOMI)
    4. Mesenteric Venous Thrombosis (MVT)
    5. Chronic Mesenteric Ischemia
  3. Supportive care to increase perfusion and oxygenation
    1. Aggressive Intravenous Fluid hydration to stabilize hemodynamic status
      1. Large fluid volumes are often required (>10 Liters on day 1 in some cases)
      2. Avoid Vasopressors
    2. Consider Blood Transfusion in Anemia
    3. Administer Supplemental Oxygen
    4. Correct acid-base abnormalities
  4. Other general measures
    1. Nasogastric suction (NG tube)
    2. Antibiotics to cover Gram-Negative Bacteria
    3. Opioid Analgesics
  5. Discontinue Vasoconstricting medications
    1. Discontinue Vasopressors
    2. Discontinue Digitalis
    3. Discontinue Beta Blockers
  6. Stabilize concurrent cardiovascular disease
    1. Congestive Heart Failure
    2. Cardiac Arrhythmia
  7. Surgical Management
    1. Exploratory laparotomy to assess for bowel viability
      1. Intraoperative Doppler Ultrasound
      2. Flourescein IV infusion with exam of bowel under wood lamp
    2. Resection of necrotic bowel
    3. Evaluate carefully for revascularization options
    4. Second-look surgery is often needed after initial stabilization
  • Prognosis
  1. Mortality: 24-94%
  • Complications
  1. Bowel Necrosis and perofation
  2. Septic Shock
  3. Death