What is the recommended diagnostic imaging approach for colonic varices (enlarged veins in the colon)?

Diagnostic Imaging of Colonic Varices

The recommended diagnostic approach for colonic varices begins with ano-proctoscopy or flexible sigmoidoscopy as first-line diagnostic tools, followed by contrast-enhanced CT scan for suspected cases, and endoscopic ultrasound (EUS) with color Doppler for definitive evaluation. 1

Initial Diagnostic Approach

• Ano-proctoscopy or flexible sigmoidoscopy should be used as the first-line diagnostic tool to identify colonic varices, which appear as discrete, compressible, and serpiginous submucosal varicose veins that cross the dentate line and extend cranially into the rectum 1
• For patients with high-risk features or evidence of ongoing bleeding, urgent colonoscopy should be performed within 24 hours of presentation 1
• Full colonoscopy is indicated when there are risk factors for colorectal cancer or suspicion of a concomitant more proximal source of bleeding 1
• Upper endoscopy should be considered in cases where a clear diagnosis of bleeding colonic varices is not established, as up to 15% of patients presenting with serious hematochezia may have an upper gastrointestinal source 1

Advanced Imaging Techniques

• Endoscopic ultrasound (EUS) with color Doppler evaluation is recommended as a second-line diagnostic tool, especially for deep rectal varices or when the diagnosis remains uncertain 1

  • EUS is superior to standard endoscopy in detecting rectal varices (85% vs 45%) and can identify varices not visible on routine endoscopy 1
  • Color Doppler examination provides detailed visualization of the entire rectal venous plexus and allows evaluation of blood flow velocity, which helps identify high-risk varices prone to rupture 1

• Contrast-enhanced CT scan is recommended when endoscopy and EUS fail to identify the bleeding source or when EUS is unavailable 1

  • CT has an overall sensitivity of up to 92% for acute hemorrhage and can detect bleeding rates as low as 0.35 ml/min 1
  • The visualization of large serpiginous veins surrounding the rectum (pararectal varices) and within the rectal wall (rectal varices) on portal venous phase images is highly suggestive of colonic varices 1
  • CT has the advantage of quick acquisition and can rule out other sources of bleeding while providing information on underlying etiologies 1

• MRI angiography should be considered in pregnant patients with bleeding colonic varices when ultrasound fails to detect the bleeding site 1

Diagnostic Algorithm

1. Initial evaluation with ano-proctoscopy or flexible sigmoidoscopy 1
2. If high-risk features or ongoing bleeding: urgent colonoscopy within 24 hours 1
3. If diagnosis remains uncertain: EUS with color Doppler evaluation 1
4. If EUS is unavailable or fails to identify bleeding source: contrast-enhanced CT scan 1
5. In pregnant patients: MRI angiography if ultrasound is inconclusive 1

Clinical Pearls and Pitfalls

• Colonic varices may be mistaken for other conditions such as hemorrhoids, tumors, or inflammatory lesions 1, 2, 3
• Colonic varices can flatten with insufflation during colonoscopy, making them difficult to diagnose with endoscopy alone 4
• CT before colonoscopy provides approximately 15% additional value for detecting vascular lesions compared to colonoscopy alone 1
• Colonic varices are most commonly associated with portal hypertension but can also occur due to splenic or portal vein thrombosis, mesenteric vein obstruction, or idiopathically 4, 5, 3
• Idiopathic colonic varices are extremely rare, with fewer than 30 cases reported in the English literature 2, 3