{GI: Other Dz}

Mesenteric Ischemia

Pathophysiology

1. Focal (arterial) or diffuse (venous) necrosis bowel due to decr blood supply; w/ arterial emboli (from heart/arrhythmia or valve dz), thrombosis, or extension of aortic dissection
2. Significant third spacing develops
3. Mucosa dies & sloughs -> bleeding
4. Bacteria crossing into tissues -> sepsis

Diagnosis

1. Pts with vascular insufficiency may present w/few symptoms, mimic other disease processes
2. Recognize risk factors: Afib, CAD, low-flow states (CHF, shock), and history of abdominal angina
3. Spectrum of illness of abdominal angina
   • Nonocclusive intestinal infarction (poor perfusion, transmural infarct +/- limited to mucosal layer)
   • Acute mesenteric infarct (occ. of SMA/ branches)
   • Mesenteric venous thrombosis (occlusion of SMV 95%; 10% of all small bowel ischemia; 70% of hx. with 2-3 days of pain, incr slowly, N/V/D; develops peritonitis)
4. Abdominal pain: crampy, dull, diffuse, worse with eating, periumbilical 15 min to 30 min post-prandial
   • Sudden onset
   • Insidious onset with venous thrombosis
   • 50% patients have a hx of abdominal angina
   • Fear of eating, weight loss
5. GI bleed (most pts); frank bleeding more indicative colonic dz, w/sm. bowel dz us. occult, rare hematochezia
6. Abdominal tenderness: pain out-of-proportion to the exam classically, +/- abdominal bruit
7. Hypovolemia, possible shock
8. +/- signs of obstruction (abdominal distension, tympany & borborygmi)
9. Labs: CBC ( leukocytosis's +/-), lytes, LFT's, lipase & amylase, CPK, LDH, PO4; metabolic acidosis without another source is hallmark of intestinal infarction
10. CXR & EKG
11. Obs. series: dilated small bowel, AF level, valvula conniventes, demonstration of arterial obstruction; may show ileus early in course
12. Angiography confirms dx: occlusion of SMA or branches.
    • MUST MAKE DX BEFORE HARD SIGNS APPEAR TO DEC. MORTALITY
13. CT: suggestive of infarction, bowel edema, ileus, calcified vessels; not standard

Treatment

1. IVF replacement prior to angiography
2. Triple antibiotics (clindamycin; 900 mg IV q8h, gentamicin 5 mg/kg IV 1st dose & 500 mg IV q8h metronidazole)
3. STAT surgical consult
   • Resection & bypass for arterial lesions
4. Anticoagulation therapy for venous lesions
5. Non-occlusive mesenteric ischemia
   • Rehydration
   • Intraarterial papaverine
   • Exploratory laparotomy if necrosis is suspected
6. Chronic mesenteric ischemia
   • If lesions are localized, bypass is a possibility
7. AVOID drugs with negative effects on circulation
   • Digoxin, propranolol, pitressin & vasopressors

Disposition

1. Admission & surgical consultation
2. If pain is mild & brief, then observe