Intestinal Ischemia

Intestinal Ischemia – Michael Koenig

Acute Mesenteric Ischemia

  • Sudden onset or absence of blood flow to the small intestines
  • Mesenteric Arterial Occlusion:
      • Arterial Embolism: Associated with cardiac arrhythmias (atrial fibrillation), valvular disease, endocarditis, ventricular aneurysm, aortic atherosclerosis, and aortic aneurysm
      • Arterial thrombosis: Most commonly from atherosclerotic disease; can also be 2/2 abdominal trauma, infection or dissection
  • Venous thrombosis:
      • Associated w/ hypercoagulable states, malignancy, prior abdominal surgery, abdominal mass venous compression, intra-abdominal inflammatory processes
  • Non occlusive mesenteric ischemia:
      • Intestinal hypoperfusion and vasoconstriction; associated w/ decreased cardiac output, sepsis, vasopressor use

 

Presentation

  • Early: Abdominal pain is most common symptom, abdominal distension
      • Abdominal tenderness is not prominent early (“pain out of proportion to the exam”)
  • Arterial occlusion: Sudden onset, severe periumbilical pain, nausea and emesis
  • Venous thrombosis: More insidious onset abdominal pain, waxing and waning
  • Nonocclusive mesenteric ischemia: variable location and severity of abdominal pain;  often overshadowed by a precipitating disorder
  • Late: As transmural bowel infarction develops, abdomen becomes distended, bowel sounds become absent, and peritoneal signs develop 

 

Evaluation

  • Type and Screen, Lactic acid, BMP, CBC
  • Imaging: KUB: Normal in > 25% of cases
      • Ileus w/ distended bowel loops, bowel wall thickening, ± pneumatosis intestinalis
      • Free intraperitoneal air immediate abdominal exploration
  • CT Angiography: no oral contrast, obscures mesenteric vessels, bowel wall enhancement
      • Focal or segmental bowel wall thickening, intestinal pneumatosis, portal vein gas, porto-mesenteric thrombosis, mesenteric arterial calcification, mesenteric artery occlusion

Management

  • General: IVFs, NPO, hemodynamic monitoring and support (try to avoid vasoconstricting agents), anticoagulation, broad-spectrum antibiotics, pain control
  • If develops peritonitis or evidence of perforation on CT EGS consult for surgery
  • Mesenteric arterial embolism: Embolectomy vs. local infusion of thrombolytic agent
  • Mesenteric arterial thrombosis: Surgical revascularization vs. thrombolysis with endovascular angioplasty and stenting
  • Venous thrombosis: Anticoagulation; possible thrombolysis if persistent symptoms
  • Nonocclusive occlusion: Treat underlying cause, stop vasoconstriction meds, consider intra-arterial vasodilator infusion. D/c anticoagulation once ischemic etiologies are excluded

 

 

Chronic Mesenteric Ischemia

  • blood flow to intestines, typically caused by atherosclerosis of mesenteric vessel
  • Also known as intestinal angina
  • High-grade mesenteric vascular stenoses in at least two major vessels (celiac, SMA, or IMA) must be established
  • Ddx: Malignancy, chronic cholecystitis, chronic pancreatitis, IBD, PUD

 

Presentation

  • Recurrent dull, crampy, postprandial abdominal pain
  • Pts develop food aversion and often have associated weight loss

 

Evaluation

  • CT angiogram abdomen/pelvis is preferred (>90% sensitivity and specificity)
  • Can also consider duplex U/S and gastric tonometry

 

Management

  • Conservative management if asymptomatic: smoking cessation and secondary prevention to limit progression of atherosclerotic disease
  • Nutritional evaluation
  • Revascularization (open vs. endovascular) is indicated if symptoms are present
    • Mesenteric angioplasty and stenting is first-line therapy
    • Goal is to prevent future bowel infarction
 

 

Ischemic Colitis

  • Sudden, transient reduction in blood flow to colon
  • Typically at “watershed” regions of colon, such as the splenic flexure and rectosigmoid junction
  • Most often nonocclusive (95% of cases) and affects older adults
  • Risk factors: ACS, hemodialysis, shock, aortoiliac instrumentation, cardio pulmonary bypass, extreme exercise (marathon running)
  • Ddx: Small bowel ischemia, infectious colitis, IBD

 

Presentation

  • Rapid onset, mild cramping abdominal pain, associated with urge to defecate, hematochezia
  • Tenderness present (typically over left side)  

 

Evaluation

  • Lactic acid (nonspecific but elevated), LDH, CPK, CBC (leukocytosis), BMP (metabolic acidosis)
  • KUB; if peritonitis or signs of severe ischemia surgery 
  • CT abdomen/pelvis w/ IV contrast (and oral contrast if patient can tolerate)
    • Edema and bowel wall thickening in segmental pattern (suggests transient ischemia and subsequent reperfusion)
  • Consider CTA abdomen/pelvis if suspicion for vascular occlusion
  • Colonoscopy confirms diagnosis. 
    • Edematous, friable mucosa; erythema; and interspersed pale areas; bluish hemorrhagic nodules representing submucosal bleeding
    • Segmental distribution, abrupt transition between injured and non-injured mucosa, rectal sparing, and single linear ulcer along longitudinal axis of colon 

 

Management

  • General: IVFs, bowel rest
  • Broad Spectrum Antibiotics: zosyn alone or CTX + flagyl
  • Risk Stratify: associated factors which predict poor outcomes
    • Male gender
    • SBP <90
    • HR >100
    • WBC >15,000
    • Hgb <12
    • Na <136
    • BUN >20
    • LDH >350
    • Isolated right-sided colonic involvement
  • Abdominal pain with rectal bleeding
  • Mild colonic ischemia (no above risk factors): sigmoidoscopy/colonoscopy and biopsy
    • Observation/supportive care; can discontinue antibiotics if no ulceration 
  • Moderate colonic ischemia (1-3 risk factors) if there is evidence of mesenteric arterial or venous occlusion then start systemic anticoagulation +/- vascular intervention
    • If no vascular occlusion, then management is the same as mild colonic ischemia
  • Severe colonic ischemia (peritoneal signs, pneumoperitoneum, pneumatosis, portal venous gas on imaging; gangrene or pancolonic ischemia on colonoscopy; >3 risk factors): consult EGS for abdominal exploration and segmental resection