What is the next best investigation with high diagnostic value for an elderly patient presenting with fresh blood per rectum, low hemoglobin (anemia), and a normal anorectal colonoscopy?

Upper GI Endoscopy is the Next Best Investigation

In an elderly patient with fresh blood per rectum, anemia (Hb 8), and normal anorectal colonoscopy, upper GI endoscopy (Option A) has the highest diagnostic value and should be performed next. 1

Rationale for Upper GI Endoscopy

Up to 15% of patients presenting with serious hematochezia actually have an upper gastrointestinal source, making upper GI endoscopy critical in the diagnostic workup when lower GI sources have been excluded. 1, 2

Key Clinical Considerations Supporting This Approach:

• Fresh blood does not reliably localize bleeding to the lower GI tract - brisk upper GI bleeding can present with hematochezia that appears identical to lower GI bleeding. 1

• Your patient has high-risk features suggesting an upper GI source:

  • Significant anemia (Hb 8) indicating substantial blood loss 1
  • Fresh blood on rectal examination despite normal colonoscopy 1
  • Elderly age, which increases likelihood of upper GI pathology 1

• A randomized trial demonstrated that 15% of patients with serious hematochezia had an upper GI source identified at upper endoscopy, and even in selected patients with diverticulosis and hematochezia, up to 8% have an upper GI bleeding source. 1, 2

Why Other Options Are Inferior:

Tc-99 Radionuclide Scanning (Option B):

• This is a second-line investigation reserved for active, ongoing bleeding when endoscopy cannot localize the source 1
• Since colonoscopy was already normal, nuclear medicine scanning would only be useful if there were active bleeding that endoscopy missed 3
• Endoscopy must be prioritized first as it offers both diagnostic AND therapeutic capability 1

CT Angiography (Option C):

• CT is recommended primarily for hemodynamically unstable patients with shock index >1, or when active bleeding is suspected and endoscopy cannot be performed 1
• CT is explicitly a second-line investigation after endoscopic evaluation has been completed 1
• Your patient needs endoscopic evaluation of the upper GI tract before proceeding to CT

Ultrasound (Option D):

• Ultrasound has no established role in the diagnostic algorithm for lower GI bleeding in this context 1

Clinical Algorithm:

1. Perform upper GI endoscopy immediately to exclude upper GI bleeding sources (peptic ulcer, gastritis, varices, Dieulafoy lesion) 1, 2

2. If upper endoscopy is negative and bleeding continues, consider:

   • Repeat colonoscopy with better preparation 3
   • Small bowel evaluation (capsule endoscopy or enteroscopy) 3
   • CT angiography if hemodynamically unstable 1
   • Radionuclide scanning if active bleeding suspected 1

Critical Pitfall to Avoid:

Do not assume that fresh red blood per rectum means lower GI bleeding - this is the most common diagnostic error in this scenario. The British Society of Gastroenterology guidelines specifically recommend that bright red rectal bleeding with concerning features should prompt senior clinical discussion about upper GI endoscopy before proceeding to other investigations. 1

Answer: A. Upper GI endoscopy