What is the role of CT (Computed Tomography) angiography in managing ulcerative colitis flare-ups?

Role of CT Angiography in Ulcerative Colitis Flares

CT angiography should be performed in patients with ulcerative colitis flares who have ongoing bleeding and are hemodynamically stable after resuscitation to localize the bleeding site before angio-embolization or surgery. 1

Diagnostic Approach in UC Flares

Initial Assessment

• Laboratory tests should include complete blood count, C-reactive protein, erythrocyte sedimentation rate, electrolytes, liver enzymes, serum albumin, and renal function 1
• Stool studies to exclude infectious causes, especially Clostridium difficile and Cytomegalovirus, are mandatory 1, 2
• Fecal calprotectin should be measured when possible to assess inflammation severity 2

Imaging Selection Algorithm

• IV contrast-enhanced CT scan is the recommended initial imaging in acute severe ulcerative colitis to exclude perforation, stenosis, bleeding, and abscesses 1
• Cross-sectional imaging (CT, MRI, ultrasonography) is essential to detect extra-luminal complications including fistulae and abscesses 1
• CT findings in ulcerative colitis typically include colonic wall thickening (mean 8mm versus normal 2-3mm), peri-colonic stranding, and sometimes ascites 2, 3

Specific Role of CT Angiography

Indications for CT Angiography

• CT angiography is specifically indicated in patients with ongoing gastrointestinal bleeding who are hemodynamically stable after resuscitation 1
• It should be performed to localize the bleeding site before angio-embolization or surgery, especially when endoscopic assessment is not available 1
• CT angiography helps in pre-operative localization of the bleeding site, allowing better planning of surgical strategy 1

Clinical Decision Points

• For patients with massive colorectal hemorrhage who are hemodynamically unstable, immediate surgery is recommended without waiting for CT angiography 1
• For stable patients with gastrointestinal bleeding, the diagnostic algorithm should start with sigmoidoscopy and esophagogastroduodenoscopy before proceeding to CT angiography 1
• CT angiography should be considered when endoscopic evaluation fails to identify the bleeding source or is not immediately available 1

Management Based on CT Angiography Findings

Surgical Indications

• Surgical treatment is recommended in patients with life-threatening bleeding and persistent hemodynamic instability 1
• Subtotal colectomy with ileostomy is the surgical treatment of choice for patients with acute severe ulcerative colitis presenting with massive colorectal hemorrhage 1
• Surgery should not be delayed in critically ill patients presenting with toxic megacolon 1

Non-surgical Management

• Hemodynamically stable patients should be evaluated in a multidisciplinary approach with gastroenterologists to decide on medical treatment options 1
• Percutaneous drainage should be considered for abscesses >3cm identified on imaging 1
• Small abscesses (<3cm) can be treated with intravenous antibiotics 1

Limitations and Considerations

Radiation Exposure Concerns

• CT scans expose patients to ionizing radiation, and patients with inflammatory bowel disease are at risk for excessive radiation exposure 4
• 63.2% of CT scans in UC patients presenting to the emergency department may have no clinically significant findings 4
• Consider MRI enterography as an alternative when available, as it provides similar diagnostic accuracy without radiation exposure 1

Potential Complications

• UC patients are at increased risk for thrombotic complications, which can be detected on CT angiography 5, 6
• Severe complications such as colonic necrosis can be identified on CT and require immediate surgical intervention 5
• Disseminated intravascular coagulation is a rare but serious complication that may be associated with severe UC flares 6

Clinical Pearls

• The diagnostic yield of CT in UC patients presenting to the emergency department may be low, with less than 2% of scans revealing complications directly related to UC 4
• Predictors of clinically significant CT findings include nausea and vomiting, history of colectomy, recent surgery, elevated white blood cell count, and not being on UC medications 4
• Point of care ultrasonography can be considered when CT is not immediately available to assess for free fluid, abscesses, or intestinal distention 1