What is the appropriate workup for a patient presenting with bright red blood in their stool?

Diagnostic Approach to Bright Red Blood in Stool

For patients presenting with bright red blood in stool, the initial workup should include assessment of hemodynamic stability, followed by anoscopy/proctoscopy, and then either sigmoidoscopy or colonoscopy depending on risk factors for colorectal cancer. 1

Initial Assessment

• Check vital signs, determine hemoglobin/hematocrit levels, and assess coagulation parameters to evaluate bleeding severity 1
• For severe bleeding, perform blood typing and cross-matching to prepare for possible transfusion 1
• Assess hemodynamic status - this will determine the urgency and sequence of diagnostic procedures 1

Diagnostic Algorithm Based on Hemodynamic Status

For Hemodynamically Unstable Patients:

• Immediate resuscitation with IV fluids and blood products to normalize blood pressure and heart rate 1
• Maintain hemoglobin above 7 g/dL (consider 9 g/dL threshold for massive bleeding or patients with cardiovascular comorbidities) 1
• Perform CT angiography (CTA) as the first-line investigation rather than endoscopy 1
• CTA can detect bleeding at rates of 0.3 mL/min and helps localize the source before potential intervention 1

For Hemodynamically Stable Patients:

1. Direct anorectal examination:

   • Anoscopy or proctoscopy should be performed first to identify common anorectal causes (hemorrhoids, fissures) 1

2. Endoscopic evaluation:

   • Upper and lower GI endoscopy should be the initial diagnostic procedures 1
   • Sigmoidoscopy or esophagogastroduodenoscopy should be performed first to rule out common sources 1
   • Full colonoscopy is indicated for patients with:
     • Age ≥55 years 2
     • Family history of colorectal neoplasia or inflammatory bowel disease 2
     • Altered bowel habits or abdominal pain 2
     • No identifiable anal source on anoscopy/proctoscopy 2
     • Blood mixed in with stool (not just on surface) 3

Important Considerations

• Even when bright red blood is present and hemorrhoids are identified, up to 6% of patients may have concurrent neoplastic lesions that could be missed without full colonoscopy 2
• Studies show that beginning with colonoscopy rather than flexible sigmoidoscopy may be more cost-effective and safer for patients with hematochezia, even when the blood is bright red 3
• If no source is identified in the upper or lower GI tract despite thorough evaluation, consider small bowel bleeding and proceed with video capsule endoscopy 4

Special Circumstances

• For patients with suspected inflammatory bowel disease and gastrointestinal bleeding, sigmoidoscopy and esophagogastroduodenoscopy should be performed first 1
• If bleeding persists despite negative initial endoscopic evaluation, consider:
  • Contrast-enhanced CT before repeat colonoscopy (improves detection rate for vascular lesions) 1
  • Nuclear medicine studies for intermittent or slow bleeding 1
  • Angiography for active bleeding that cannot be localized by endoscopy 1

Common Pitfalls to Avoid

• Assuming bright red blood always indicates a distal source - up to 10% of bright red hematochezia may come from more proximal sources, including cancer 3
• Stopping at identification of hemorrhoids without considering concurrent pathology 2
• Delaying CTA in unstable patients - this should be performed before endoscopy in hemodynamically compromised patients 1
• Failing to consider upper GI sources, which can present with bright red rectal bleeding in cases of rapid transit 1