What is the appropriate workup and management for an adult presenting with rectal bleeding, taking into account hemodynamic status, age, risk factors for colorectal cancer, and potential anorectal sources?

Rectal Bleeding Workup

Immediate Hemodynamic Assessment

Begin by immediately checking vital signs, hemoglobin/hematocrit, and coagulation parameters to determine bleeding severity and guide the urgency of your diagnostic and therapeutic approach. 1, 2

• Establish two large-bore IV lines if the patient shows any signs of hemodynamic compromise (tachycardia >100 bpm, systolic BP <100 mmHg, or orthostatic changes) 2, 3
• Perform blood typing and cross-matching if severe bleeding is evident 4, 1
• Calculate the Oakland score to stratify risk: scores >8 require admission with urgent colonoscopy within 24 hours, while scores ≤8 can be discharged for outpatient investigation within 2 weeks 2

Resuscitation Protocol for Hemodynamically Unstable Patients

If the patient is hemodynamically unstable (MAP <65 mmHg, HR >100, SBP <100), immediately infuse 1-2 L of crystalloid and transfuse packed red blood cells to maintain hemoglobin >7 g/dL (>10 g/dL in elderly patients with cardiovascular comorbidities) before any diagnostic procedures. 2, 3

• Target mean arterial pressure >65 mmHg while avoiding fluid overload 4, 2, 3
• Correct coagulopathy with fresh frozen plasma if INR >1.5 3
• Monitor urine output targeting ≥30 mL/hour as an indicator of adequate perfusion 3
• Do not proceed with colonoscopy until hemodynamic stability is achieved—performing endoscopy in unstable patients markedly increases risk of aspiration, cardiovascular events, and mortality 3

Diagnostic Algorithm Based on Hemodynamic Status

For Hemodynamically Unstable Patients (After Initial Stabilization):

Perform CT angiography as the first-line investigation to rapidly localize active bleeding without requiring bowel preparation. 1

• CTA has sensitivity of 79-95% and specificity of 95-100% for detecting active bleeding when the rate exceeds 0.3-1.0 mL/min 1
• If CTA is negative, perform upper endoscopy immediately to exclude an upper GI source, as 10-15% of patients with severe hematochezia have upper GI bleeding 1, 2, 3
• Once fully stabilized, proceed to colonoscopy within 24 hours with adequate bowel preparation 2, 3

For Hemodynamically Stable Patients:

Begin with direct anorectal examination using anoscopy or proctoscopy to identify common anorectal sources such as hemorrhoids or fissures. 1, 2

• If anoscopy is negative and the patient has high-risk features (ongoing bleeding, age >50, risk factors for colorectal cancer), perform colonoscopy within 24 hours 4, 2
• Ensure adequate bowel preparation with polyethylene glycol solutions to improve diagnostic yield 2
• If colonoscopy is negative, perform upper endoscopy as 8-15% of stable patients with rectal bleeding have an upper GI source 1, 2

Age and Colorectal Cancer Risk Considerations

All patients ≥45 years presenting with rectal bleeding require full colonoscopy to exclude colorectal cancer, as 20% of CRC cases now occur in patients younger than 55 years. 5, 6

• Rectal bleeding is the most common presenting symptom of CRC (58% of cases), followed by abdominal pain (52%) and change in bowel habits (51%) 7
• Right-sided colon cancers are more likely to present with anemia and proximal symptoms (anorexia, nausea, vomiting, abdominal pain), while left-sided and rectal cancers more commonly present with visible rectal bleeding and constipation 7
• The proportion of rectal cancers has increased from 27% in 1995 to 31% in 2019, with a concerning shift toward more advanced stage at diagnosis 5

Special Scenario: Suspected Anorectal Varices

If you suspect anorectal varices based on history of portal hypertension or cirrhosis, use ano-proctoscopy or flexible sigmoidoscopy as the first-line diagnostic tool. 4, 2

• Perform urgent colonoscopy plus upper endoscopy within 24 hours if high-risk features or ongoing bleeding are present 4
• Consider endoscopic ultrasound with color Doppler as a second-line tool for deep rectal varices 4, 1
• Initiate vasoactive drugs (terlipressin or octreotide) to reduce splanchnic blood flow and portal pressure 2
• Administer prophylactic antibiotics and temporarily suspend beta-blockers during acute bleeding 2
• Maintain hemoglobin >7 g/dL but avoid over-transfusion, which may increase portal pressure and worsen bleeding 4, 2

Critical Pitfalls to Avoid

• Never delay resuscitation to perform diagnostic procedures—stabilization always takes priority 2
• Never attempt colonoscopy in hemodynamically unstable patients—this dramatically increases mortality risk 3
• Never assume a lower GI source in severe bleeding—always consider upper GI bleeding, especially with hemodynamic instability 1, 2, 3
• Never rely on inadequate bowel preparation—poor visualization leads to missed diagnoses and repeat procedures 2
• Never over-transfuse patients with portal hypertension—this may increase portal pressure and worsen variceal bleeding 2