What is the initial workup for a patient presenting with hematochezia (blood in stool)?

Initial Workup for Hematochezia (Blood in Stool)

The initial workup for a patient presenting with hematochezia should include assessment of hemodynamic stability, followed by anoscopy/proctoscopy, and then either sigmoidoscopy or colonoscopy depending on the severity of bleeding and patient risk factors. 1

Initial Assessment

• Evaluate hemodynamic stability by checking vital signs, determining hemoglobin/hematocrit levels, and assessing coagulation parameters 1
• For severe bleeding, perform blood typing and cross-matching to prepare for possible transfusion 1
• Use the Oakland score to classify bleeding severity - a score >8 points indicates a major bleed requiring hospital admission 2
• Consider that 10-15% of apparent lower GI bleeding may actually have an upper GI source, especially in patients with severe hematochezia and hypovolemia 2, 3

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 2, 3, 1
• CTA can detect bleeding at rates of 0.3 mL/min and helps localize the source before potential intervention 1
• If a patient has a shock index (heart rate/systolic BP) of >1 after initial resuscitation and/or active bleeding is suspected, CTA provides the fastest and least invasive means to localize the bleeding site 2, 3

For Hemodynamically Stable Patients:

• Direct anorectal inspection with anoscopy or proctoscopy should be performed first, especially when bright red rectal bleeding is present 3, 1
  • This allows immediate identification of common anorectal sources such as hemorrhoids, which account for approximately 14% of lower GI bleeding 3
  • In the national audit, benign anorectal conditions accounted for 16.7% of diagnoses 2
• For patients with a minor self-terminating bleed (Oakland score ≤8 points) with no other indications for hospital admission, discharge for urgent outpatient investigation is appropriate 2
  • These patients should have outpatient colonoscopy within 2 weeks, especially if aged over 50, due to 6% risk of underlying bowel cancer 2
• For patients with a major bleed (Oakland score >8 points), admit to hospital for colonoscopy on the next available list 2
  • Colonoscopy has diagnostic yields of 42-90% and allows for therapeutic intervention 2
  • Patients should receive bowel preparation to enable adequate mucosal visualization 2

Special Considerations

• If upper GI bleeding is suspected, perform nasogastric lavage and/or upper endoscopy 2
  • If blood, clots, or coffee grounds-appearing material is present in the NG aspirate, upper endoscopy must be performed 2
• For patients with suspected inflammatory bowel disease and gastrointestinal bleeding, sigmoidoscopy should be performed early 1
• If colonoscopy does not identify a bleeding source, consider small bowel evaluation 2
• Urgent colonoscopy (within 24 hours) has been shown to reduce length of hospital stay but may result in higher rates of recurrent bleeding compared to standard colonoscopy (within 1-3 days) 4

Common Pitfalls to Avoid

• Failing to consider an upper GI source in patients with severe hematochezia (10-15% of cases) 2, 3
• Proceeding directly to colonoscopy without first examining the anorectal region, potentially missing easily identifiable sources 3, 1
• Delaying CTA in unstable patients - this should be performed before endoscopy in hemodynamically compromised patients 1
• Using nasogastric tube placement alone to rule out upper GI bleeding, as this is not reliable 3
• Delaying appropriate imaging in unstable patients while attempting bowel preparation for colonoscopy 3