Intestinal 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

• ↓ 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

• 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