Mesenteric Ischemia

Aka: 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

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II. Definitions

  1. Acute Mesenteric Ischemia
    1. Sudden interruption of Small Bowel perfusion resulting in Intestinal Ischemia, infarction and necrosis

III. 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

IV. 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 infarction (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

V. Epidemiology

  1. Uncommon condition (but requires high index suspicion)
    1. Accounts for 0.1 to 1% of Acute Abdominal Pain admissions
    2. Mortality is as high as 24-94%
    3. Rapid diagnosis is critical to survival
  2. More common in patients over age 60 years old
  3. More common in women (3 fold increased risk over men)

VI. Risk Factors

  1. Advanced age over 60 to 70 years old
  2. Female gender (3 fold increased risk over men)
  3. Intra-Abdominal Cancer
  4. Comorbid Cardiovascular Disease
    1. Atherosclerosis (e.g. Coronary Artery Disease, Peripheral Arterial Disease)
    2. Atrial Fibrillation
      1. Causes 50% of Mesenteric Artery Embolism, and 25% of all Mesenteric Ischemia cases
    3. Dilated Cardiomyopathy
      1. Reduced ejection fraction is a risk for splanchnic Vasoconstriction and Nonocclusive Mesenteric Ischemia (NOMI)
  5. Endocarditis Risk
    1. Valvular Disease
    2. Intravenous Drug Use
  6. Other Comorbidity
    1. Diabetes Mellitus
    2. Hypertension
    3. Renal Insufficiency
    4. Vasculitis
    5. Hypercoagulable state (Mesenteric Venous Thrombosis)
  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

VII. Causes: Primary Acute Mesenteric Ischemia (intravascular)

  1. Mesenteric Artery Embolism (50%)
    1. Most common embolism source is of cardiac origin (e.g. Atrial Fibrillation, endocarditis, Cardiomyopathy, Myocardial Ischemia)
      1. Atrial Fibrillation is responsible for 50% of cases
    2. Superior Mesenteric Artery Embolism is affected in most cases (large bore vessel with narrow angle branch from aorta)
      1. More than half lodge distal to the middle colic artery origin (typically 6-8 cm from SMA origin)
      2. Affects Midgut (Small Intestine and proximal colon to splenic flexure), sparing the jejunum and colon
  2. Mesenteric Artery Thrombosis (15-25%)
    1. Superior Mesenteric Artery (SMA) thrombosis of stenotic, atherosclerotic vessels, typically at proximal SMA
    2. Often preceded by Chronic Mesenteric Ischemia (postprandial Abdominal Pain and weight loss)
  3. Nonocclusive Mesenteric Ischemia - NOMI (20-30%)
    1. Results from Low Cardiac Output (shock) and mesenteric arterial Vasoconstriction or vasospasm (severe and prolonged)
    2. Causes include Septic Shock, Cardiogenic Shock, Hypovolemic Shock, Cardiomyopathy and Bowel Obstruction with Strangulation
    3. Bowel can compensate for up to 12 hours with increased oxygen extraction, increased capillary recruitment
  4. Mesenteric Venous Thrombosis - MVT (5-10%)
    1. Occurs in Hypercoagulable State or localized intraabdominal inflammation (e.g. Trauma, Pancreatitis, Sepsis, Inflammatory Bowel Disease)
    2. Typically associated with underlying diffuse atherosclerosis and Chronic Mesenteric Ischemia
    3. Most commonly affects the superior mesenteric vein and its branches
    4. Results in bowel wall edema and elevated vascular resistance with secondary decreased arterial flow

VIII. Causes: Primary Chronic Mesenteric Ischemia (abdominal or Intestinal Angina)

  1. See Chronic Mesenteric Ischemia
  2. Presents with postprandial Abdominal Pain, weight loss and food aversion
  3. Diffuse atherosclerotic disease in 95% of cases
    1. All major mesenteric vessels (SMA, IMA, Celiac Artery) with stenosis or Occlusion

IX. Causes: Secondary Mesenteric Ischemia (compression)

  1. Adhesions
  2. Herniation
  3. Volvulus
  4. Intussusception
  5. Tumor
  6. Trauma
  7. Retroperitoneal fibrosis

X. Precautions

  1. Have a low index of suspicion in Abdominal Pain out of proportion in older patients or Atrial Fibrillation

XI. Symptoms

  1. Abdominal Pain (95% of cases)
    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. Provocative
    1. Postprandial pain onset 10 to 30 minutes after a meal
  3. 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
  4. Gastroenteritis-type symptoms (one third of cases)
    1. Diarrhea (35% of cases) progressing to Constipation
      1. Superior Mesenteric Artery Embolism
      2. Superior Mesenteric Artery Thrombosis
    2. Nausea (44% of cases) or Vomiting (35% of cases)
      1. Superior Mesenteric Artery Embolism
      2. Mesenteric Venous Thrombosis
      3. Chronic Mesenteric Ischemia
  5. Chronic Malnutrition, Cachexia or Wasting Syndrome (food avoidance, Malnutrition and weight loss)
    1. Chronic Mesenteric Ischemia (Abdominal Angina)
  6. Associated Findings
    1. Bloody stools (10 to 16% of cases)

XII. Signs

  1. Abdominal exam may be benign early in course
    1. Abdominal Pain is typically out of proportion to exam
  2. Peritonitis and systemic features in delayed presentation once infarction and necrosis has occurred (1-3 days after onset)
    1. Acute Abdomen is found in 20 to 25% of cases
    2. Abdominal tenderness to palpation
    3. Fever
    4. Fecal Occult Blood positive in 25% of cases
    5. Ill appearance
  3. Other findings
    1. Abdominal bruit (>17% of cases)

XIII. Labs: Diagnosis

  1. Precautions
    1. No laboratory test has Test Sensitivity or Test Specificity to rule-in or rule-out Mesenteric Ischemia
  2. Serum lactate
    1. Most useful laboratory test when considering Mesenteric Ischemia as a diagnosis, as well as serial re-testing
    2. Elevated Lactic Acid in Mesenteric Ischemia suggests severe segmental ischemia or infarction has already occurred
    3. Normal Lactic Acid does not exclude Mesenteric Ischemia, and intervention is ideally before Lactic Acid rises
    4. Test Sensitivity: 86%
    5. Test Specificity: 44%
    6. Cudnik (2013) Acad Emerg Med 20(11): 1087-1100 [PubMed]
  3. Complete Blood Count (CBC)
    1. Leukocytosis >15k (and often over 20k) with Left Shift is common (may be absent in Immunocompromised patients)
  4. Other labs abnormal if prolonged bowel ischemia, infarction, necrosis or perforation occurs
    1. Arterial Blood Gas (ABG) or Venous Blood Gas (VBG) with Metabolic Acidosis
    2. Serum Amylase increased
    3. Serum Phosphate Level
      1. Increases within 4 hours (75%)
    4. Procalcitonin increased
      1. Cosse (2014) World J Gastroenterol 20(47): 17773-8 [PubMed]
    5. D-Dimer increased
      1. D-Dimer, although non-specific, is elevated in most Mesenteric Ischemia cases
      2. May be useful for its high Negative Predictive Value (unlikely to be Mesenteric Ischemia when negative)
      3. Block (2008) Scand J Clin Lab Invest 68(3): 242-8 [PubMed]
    6. Intestinal Fatty Acid Binding Protein (I-FABP)
      1. I-FABP is released from injured intestinal mucosal villi
      2. Not available outside of experimental protocols as of 2022
      3. Test Sensitivity: 80%
      4. Test Specificity: 86%
      5. Montagnana (2018) Ann Transl Med 6(17): 341 [PubMed]
  5. Malnutrition Labs in Chronic Mesenteric Ischemia
    1. Anemia
    2. Leukopenia or Lymphopenia
    3. Hypoalbuminemia
  6. Electrocardiogram (EKG)
    1. Obtain in all patients with suspected Mesenteric Ischemia

XIV. Labs: Other to Evaluate Differential Diagnosis and Comorbidities

  1. Comprehensive metabolic panel (e.g. Chem18)
    1. Serum Electrolytes
    2. Renal Function tests
      1. Blood Urea Nitrogen (BUN)
      2. Serum Creatinine
    3. Liver Function Tests (LFT)
      1. AST increased
  2. 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
  3. Coagulation Studies
    1. ProTime (INR)
    2. Partial Thromboplastin Time (PTT)
    3. Consider Hypercoagulable lab studies in Mesenteric Venous Thrombosis
  4. Miscellaneous
    1. Lactate Dehydrogenase (LDH) Increased
    2. Creatine Phosphokinase (CK-MM) Increased
    3. Serum Lipase
    4. Type and Cross Match Blood

XV. Differential Diagnosis

  1. See Acute Abdominal Pain
  2. See Acute Abdominal Pain Causes
  3. See Abdominal Pain in Older Adults

XVI. Imaging: Advanced (Preferred)

  1. CT Abdomen Pelvis with CT Angiography
    1. First-line study in most cases
    2. Perform with CT angiography timing and contrast load to best assess bowel perfusion
      1. Thin slices (1 to 3 mm)
      2. Do not use Oral Contrast (obscures mesenteric vessels and bowel wall enhancement)
    3. Efficacy
      1. Test Sensitivity: 71-96%
      2. Test Specificity: 92-94%
    4. Progression of bowel changes in Mesenteric Ischemia
      1. Mesenteric Edema and stranding
      2. Bowel dilation
      3. Bowel wall thickening (edema, Hemorrhage)
      4. Bowel wall gas (pneumotosis intestinalis) and Portal Vein gas in necrosis
    5. Findings in Mesenteric Venous Thrombosis
      1. Best performed with two-phase imaging (enhances visceral venous drainage)
      2. Mesenteric vein or Portal Vein engorgement
      3. Visceral edema
    6. 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
    7. Findings in Nonocclusive Mesenteric Ischemia (NOMI)
      1. Segmental narrowing of major arteries
      2. Small vessel decreased flow
  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 may be best modality to fully evaluate for abdominal vascular disease
    2. However, multiple limitations (beyond long scan times and decreased availability compared with CT)
      1. Poorly evaluates distal mesenteric vessels
      2. Poor sensitivity for bowel wall thickening or mesenteric stranding
    3. Indications (typically non-emergent evaluation)
      1. Limited use in the acute setting
      2. Chronic Mesenteric Ischemia (ideal imaging)
      3. Acute Mesenteric Venous Thrombosis
      4. Intravenous Contrast dye allergy
  4. Mesenteric Duplex Ultrasound
    1. Evaluates only proximal, main vessels (SMA, IMA and Celiac Artery), identifying high peak systolic velocity
    2. Consider in suspected Chronic Mesenteric Ischemia
    3. Test Sensitivity: 70-89%
    4. Test Specificity: 92-100% (approaches 100% for SMA Occlusion)
    5. Ultrasound is useful in combination with angiography following visceral bypass graft or endovascular stenting
    6. Limited Test Sensitivity due to overlying bowel gas that may interfere with study

XVII. Imaging: Abdominal XRay (or KUB, Kidney-ureter-Bladder)

  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
      1. Suggests mucosal and submucosal edema or Hemorrhage
      2. Multiple round, smooth, soft tissue markings in the bowel lumen
    3. Bowel wall thickening
  4. Findings suggestive of intestinal infarction (late finding)
    1. Air in bowel wall (Pneumatosis Intestinalis)
    2. Air in Portal Vein
  5. Other conditions identified
    1. Small Bowel Obstruction
      1. Air-fluid levels
      2. Fixed dilated loops of bowel
    2. Volvulus
    3. Viscus perforation

XVIII. Management: General

  1. Immediate Vascular Surgery Consultation (or General Surgery if not available)
  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. Adjust based on hemodynamic monitoring parameters
      2. Large fluid volumes are often required (>10 Liters on day 1 in some cases)
      3. Avoid Vasopressors in general
        1. May consider in Hypotension and volume overload
        2. May consider in prevention of Abdominal Compartment Syndrome
        3. If used, consider low dose Dopamine, Dobutamine or milrinone (less mesenteric Vasoconstriction)
    2. Consider Blood Transfusion in Anemia
    3. Administer Supplemental Oxygen
    4. Correct acid-base and Electrolyte abnormalities
      1. Serially follow Electrolytes (e.g. Hyperkalemia)
      2. Serially follow Venous Blood Gas (risk of severe Metabolic Acidosis)
  4. Infection control
    1. Mesenteric Ischemia disrupts the mucosal barrier and allows for Bacterial translocation and Sepsis risk
    2. Start empiric broad spectrum antibiotics to cover Gram-Negative Bacteria and Anaerobic Bacteria
      1. Piperacillin and Tazobactam (Zosyn) OR
      2. Ceftriaxone AND Metronidazole
  5. Other general measures
    1. Nasogastric suction (NG tube)
    2. Opioid Analgesics
    3. Heparin Anticoagulation indications
      1. Acute Mesenteric Ischemia
      2. Chronic Mesenteric Ischemia with exacerbation
  6. Discontinue Vasoconstricting medications
    1. Discontinue Vasopressors
    2. Discontinue Digitalis
    3. Discontinue Beta Blockers
  7. Stabilize concurrent cardiovascular disease
    1. Congestive Heart Failure
    2. Cardiac Arrhythmia

XIX. Management: Surgical

  1. Consult Vascular Surgery or General Surgery
  2. Indications for emergent exploratory laparotomy
    1. Acute Abdomen with peritoneal signs or peritonitis
    2. Intestinal infarction
    3. Intestinal perforation
    4. Gastrointestinal Bleeding
  3. Open Surgery
    1. Exploratory laparotomy
      1. 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. Revascularization
        1. Evaluate carefully for revascularization options and revascularize where possible
        2. Surgical embolectomy for proximal Superior Mesenteric Artery Embolism
    2. Complications
      1. Second-look surgery is often needed after initial stabilization (>50% of cases)
      2. Open surgery is associated with longer hospital stay and prolonged recovery compared with endovascular repair
      3. Short-term or in-hospital mortality: 26 to 65%
        1. Increased mortality in advanced age, delayed intervention, Metabolic Acidosis, Renal Insufficiency
  4. Endovascular Repair
    1. Indicated in high risk patients with severe comorbidity
    2. Revascularization via thrombectomy or Angioplasty with stenting (87% successful)
    3. Short-term or in-hospital mortality: 25%
    4. Beaulieu (2014) J Vasc Surg 59(1): 159-64 [PubMed]

XX. Prognosis

  1. Mortality: 24-94%

XXI. Complications

  1. Bowel Necrosis and perforation
  2. Septic Shock
  3. Abdominal Compartment Syndrome
  4. Death

XXII. References

  1. Fraboni (2012) Board Review Express, San Jose
  2. Birnbaumer (2001) CMEA Medicine Lecture, San Diego
  3. Kern and Gilley-Avramis (2022) Crit Dec Emerg Med 36(11) 21-8
  4. Harward (1989) J Vasc Surg 9(2): 328-32 [PubMed]
  5. Jamieson (1982) Br J Surg 69:S52 [PubMed]
  6. Kairaluoma (1977) Am J Surg 133:188 [PubMed]
  7. Mastoraki (2021) World J Gastrointest Pathophysiol 7(1): 125-30 [PubMed]
  8. Wolk (1981) Int Surg 65(3):231 [PubMed]

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