Mesenteric Ischemia

Basics

Description

  • Decreased or occluded blood flow through the mesenteric vessels leading to ischemia or infarction of bowel
  • Can be from arterial or venous blockage, or low flow states
  • 1 in 1,000 of all ED presentations
  • 1–2% of all admissions for abdominal pain:
    • Most cases occur in patients >50 yr
    • Mortality as high as 60–70%, particularly if diagnosis/presentation delayed >24 hr

Etiology

  • Acute mesenteric arterial embolism:
    • 50% of cases of acute mesenteric ischemia
    • Mean age 70 yr
    • Emboli most commonly arise in left atria or ventricle, from a dysrhythmia, valvular lesions, or ventricular thrombus from a prior MI
    • Typically lodge 3–10 cm distal to the origin of the superior mesenteric artery (SMA):
      • Preserves blood flow to proximal small and large bowel
    • Risk factors include dysrhythmia (especially atrial fibrillation), valvular heart disease, prior MI, aortic aneurysm, or dissection
  • Mesenteric artery thrombus:
    • SMA thrombus in 15% of cases of acute mesenteric ischemia
    • Rare in other vessels
    • Develops from plaque rupture of mesenteric atherosclerotic disease
    • 50–80% may have longstanding intestinal angina (chronic mesenteric ischemia)
    • Risk factors include age, atherosclerotic disease, HTN
  • Mesenteric venous thrombosis:
    • 5–15% of cases of acute mesenteric ischemia
    • Subacute/indolent presentation
    • 20–40% mortality
    • Typically occurs in younger patients with underlying hypercoagulable state
    • Risk factors include:
      • Hypercoagulable state (lupus, protein C and S deficiency)
      • Sickle cell disease
      • Antithrombin III deficiency
      • Malignancy (particularly portal)
      • Pregnancy
      • Sepsis
      • Renal failure on dialysis
      • Estrogen therapy
      • Recent trauma or inflammatory conditions
  • Nonocclusive mesenteric ischemia:
    • 20–30% of cases of acute mesenteric ischemia
    • Occurs in low cardiac output states with decreased mesenteric blood flow
    • Risk factors include CHF, sepsis, hypotension, hypovolemia, diuretic use, recent surgery (especially cardiac), or recent vasopressor requirement
    • Poorer survival rates
  • Chronic mesenteric ischemia:
    • “Intestinal angina”:
      • Postprandial, diffuse abdominal pain occurring ∼1 hr after eating, lasts 1–2 hr
      • Patients may develop food aversions and eat small meals to avoid pain
  • Uncommon causes:
    • Spontaneous mesenteric arterial dissection
    • Median arcuate ligament syndrome – compression of the celiac axis or SMA by the arcuate ligament of the diaphragm
    • Extrinsic compression from tumors
    • Medications:
      • Digitalis
      • Ergotamine
      • Cocaine
      • Pseudoephedrine
      • Vasopressin

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