What is the role of an angiogram in diagnosing and treating ischemic colitis?

Role of Angiography in Ischemic Colitis

CT angiography (CTA) has replaced conventional angiography as the first-line imaging technique for diagnosing ischemic colitis, with conventional angiography now primarily serving as a complementary diagnostic and therapeutic tool for selected cases. 1, 2

Diagnostic Role of Angiography

CT Angiography (CTA)

• CTA of the abdomen and pelvis is the recommended first-line imaging test for suspected ischemic colitis due to its high sensitivity (95-100%) and specificity for detecting vascular abnormalities 2
• CTA is fast, accurate, and widely available, making it ideal for rapid diagnosis in this potentially life-threatening condition 1
• Triple-phase CTA (non-contrast, arterial, and portal venous phases) is optimal for identifying the underlying cause and evaluating for bowel complications 2
• CTA can assess both arterial and venous occlusions while simultaneously evaluating for signs of bowel ischemia 2

Conventional Angiography

• Historically considered the reference standard for diagnosing mesenteric ischemia with sensitivity of 74-100% and specificity of 100% 1
• Now primarily used as a second-line diagnostic tool when CTA results are inconclusive or negative but clinical suspicion remains high 1
• Lateral aortography is best suited for displaying the typical origin lesions of intestinal arteries that may not be apparent on frontal projections 1
• Conventional angiography should not be considered in patients with significant hypovolemia or hypotension 1

Therapeutic Role of Angiography

• Conventional angiography allows for both diagnosis and potential treatment in the same session 1, 2
• Endovascular treatment options include:
  • Selective catheterization for intra-arterial vasodilator therapy in non-occlusive ischemia 1
  • Thrombolysis for acute thrombotic occlusions 2
  • Angioplasty and stenting for stenotic lesions 1
• The endovascular approach is becoming more common and is associated with decreased mortality and reduced need for laparotomy compared to open surgery 1
• Technical success of embolization is above 95%, although up to 25% of patients may present later with recurrent bleeding 1

Clinical Decision Algorithm

1. Initial Presentation: Patient with suspected ischemic colitis (abdominal pain, bloody diarrhea)

   • First imaging choice: CTA abdomen/pelvis with triple-phase protocol 2
   • If CTA unavailable or contraindicated: Consider MRA or duplex ultrasound 1, 2

2. If CTA shows definitive findings:

   • Non-gangrenous ischemic colitis without signs of peritonitis: Conservative management 3
   • Gangrenous ischemic colitis or signs of peritonitis: Urgent surgical intervention 4

3. If CTA is inconclusive but clinical suspicion remains high:

   • Consider conventional angiography for further evaluation 1
   • Particularly valuable if distal disease is suspected 2

4. Therapeutic angiography indications:

   • Hemodynamically stable patients with active bleeding identified on CTA 1
   • Patients with recurrent intermittent bleeding where other modalities have failed 1
   • Patients who are poor surgical candidates 1

Important Caveats and Pitfalls

• CT angiogram performed after diagnosis of ischemic colitis may not provide additional information that alters management or prognosis 5
• In the absence of active extravasation at angiography, embolization should not be performed 1
• Risk of bowel ischemia after embolization is up to 10%, though most patients are asymptomatic 1
• Delayed diagnosis significantly increases mortality, which can be as high as 50-80% if untreated 6
• Time to diagnosis and intervention is critical - early angiography has been associated with increased survival 1
• Whether angiography should precede surgical intervention in the presence of peritoneal signs is controversial - some favor immediate surgery as peritonitis usually indicates infarcted bowel 1

Special Considerations

• For chronic mesenteric ischemia, diagnostic angiography including lateral aortography should be obtained when noninvasive imaging is unavailable or indeterminate 1
• Duplex ultrasound can be used as an initial screening tool for chronic mesenteric ischemia with sensitivity and specificity of 85-90% for detecting proximal mesenteric artery stenosis 1, 2
• Most cases of non-gangrenous ischemic colitis are transient and resolve spontaneously without complications, not requiring angiographic intervention 4
• Gangrenous ischemic colitis typically requires urgent surgical intervention rather than angiographic management 3