What is the initial workup for a hemodynamically unstable adult patient with no significant past medical history presenting to the emergency department (ED) with bright red blood per rectum?

Initial Workup for Bright Red Blood Per Rectum in the ED

For a hemodynamically unstable patient presenting with bright red blood per rectum, perform CT angiography (CTA) immediately as the first-line investigation, followed by upper endoscopy if no source is identified. 1

Immediate Assessment and Resuscitation

• Calculate the shock index (heart rate divided by systolic blood pressure) immediately upon presentation—a value ≥1 defines hemodynamic instability and dictates the diagnostic pathway 1, 2
• Obtain hemoglobin/hematocrit, type and cross-match blood, and check coagulation parameters 2
• Begin aggressive resuscitation with intravenous crystalloids and packed red blood cells to maintain hemoglobin >7 g/dL, but avoid fluid overload which can exacerbate portal pressure and worsen bleeding 1, 2
• Maintain mean arterial pressure >65 mmHg during resuscitation 1

Diagnostic Algorithm for Unstable Patients (Shock Index ≥1)

First-Line Investigation: CT Angiography

• Proceed directly to CTA without delay—do not attempt colonoscopy first in unstable patients 1, 2
• CTA has 79-95% sensitivity and 95-100% specificity for detecting active bleeding at rates of 0.3-1.0 mL/min 1, 2
• CTA is superior to colonoscopy in unstable patients because it:
  • Localizes bleeding in the upper GI tract, small bowel, or colon without bowel preparation 1
  • Is rapidly accessible and widely available 1
  • Guides subsequent therapeutic interventions (embolization, surgery, or targeted endoscopy) 1

Second-Line Investigation: Upper Endoscopy

• If CTA identifies no bleeding source, perform immediate upper endoscopy to exclude an upper GI source, as 8-15% of patients with bright red rectal bleeding have upper GI bleeding despite the presentation 1
• Risk factors suggesting upper GI source include: brisk rectal bleeding with hemodynamic compromise, history of peptic ulcer disease, portal hypertension, elevated BUN/creatinine ratio, and antiplatelet drug use 1
• Do not place a nasogastric tube—it does not reliably aid diagnosis, does not affect outcomes, and causes complications in one-third of patients 1, 2

Third-Line Investigation: Anorectal Examination and Colonoscopy

• Perform direct anorectal inspection (anoscopy) as bright red bleeding may indicate an anorectal source such as hemorrhoids or fissures 1, 2
• If anoscopy and CTA are both negative, proceed to full colonoscopy to visualize the entire lower GI tract 1

Diagnostic Algorithm for Stable Patients (Shock Index <1)

• Begin with direct anorectal examination and anoscopy to identify common anorectal causes 1, 2
• Consider upper endoscopy if there are risk factors for upper GI bleeding or if lower endoscopy is negative, as up to 8% of patients with presumed lower GI bleeding have an upper source 1
• Proceed to colonoscopy for definitive evaluation of the colon if anorectal examination is unrevealing 1, 2

Additional Investigations if Initial Workup is Negative

• Nuclear medicine studies (red cell scintigraphy) offer 60-93% sensitivity for intermittent or slow bleeding when CTA, angiography, and colonoscopy are negative 1
• Video capsule endoscopy permits examination of the small bowel in 79-90% of patients with overt-obscure GI bleeding after negative upper and lower endoscopy 1, 2
• Repeat CTA is not beneficial unless bleeding becomes more brisk 1
• Mesenteric angiography is unlikely to be positive within 24 hours of a negative CTA in stable patients 1

Critical Pitfalls to Avoid

• Never delay CTA by attempting colonoscopy first in unstable patients—colonoscopy requires bowel preparation, cannot localize upper GI or small bowel sources, and delays definitive diagnosis 1, 2
• Do not assume hemorrhoids are the source without complete evaluation, especially in patients ≥45 years or with risk factors for colorectal neoplasia 3
• Do not rely on nasogastric tube placement to diagnose or exclude upper GI bleeding 1, 2
• Avoid over-resuscitation with excessive fluids, which can increase portal pressure and worsen variceal bleeding 1

Special Populations

Inflammatory Bowel Disease

• Perform sigmoidoscopy and esophagogastroduodenoscopy as first-line evaluations in stable IBD patients with GI bleeding 1, 2
• Proceed to immediate surgery for unstable patients with hemorrhagic shock non-responsive to resuscitation 1

Suspected Anorectal Varices

• Involve hepatology specialists early and optimize portal hypertension management 1
• Consider endoscopic ultrasound with color Doppler as a second-line diagnostic tool 2
• Endorectal compression tubes may serve as a bridging maneuver for stabilization or transfer 1

History of Aortic Surgery

• Immediate hospital assessment is mandatory due to risk of aortoenteric fistula 3