What is the differential diagnosis and management for a patient presenting with rectal bleeding?

Differential Diagnosis and Management of Rectal Bleeding

Immediate Risk Stratification

Calculate the shock index (heart rate ÷ systolic blood pressure) immediately upon presentation—a value >1 indicates hemodynamic instability requiring urgent intervention rather than routine endoscopy. 1, 2

Oakland Score for Lower GI Bleeding Risk Assessment

Use the Oakland score to determine disposition for hemodynamically stable patients 3, 2:

• Score ≤8 points: Safe for immediate discharge with urgent outpatient colonoscopy within 2 weeks 3
• Score >8 points: Requires hospital admission for inpatient evaluation 3

The Oakland score incorporates: age, gender, previous LGIB admission, blood on digital rectal exam, heart rate, systolic blood pressure, and hemoglobin level 3, 2

Differential Diagnosis by Category

Common Benign Anorectal Causes (16.7% of cases)

• Hemorrhoids: Most common cause, typically presents with bright red blood on toilet paper or coating stool 3, 4
• Anal fissures: Associated with severe pain during defecation 3
• Anorectal abscesses: Present with acute anal pain and possible fever 3

Colonic Pathology

• Colorectal cancer: Present in 6% of patients presenting with LGIB; risk increases significantly over age 50 3, 4
• Polyps: Found in 25% of patients over age 40 with rectal bleeding, with 17% having polyps ≥5mm 4
• Diverticular disease: Accounts for approximately 16% of bleeding cases 4
• Inflammatory bowel disease: Found in 11% of patients over 40 presenting with rectal bleeding 4, 5

Radiation-Induced Bleeding

• Radiation proctitis: Presents with telangiectasia causing chronic bleeding in patients with prior pelvic radiation 3

Upper GI Sources

• Always consider upper GI bleeding in patients with hemodynamic instability, even when presenting with bright red rectal bleeding, as UGIB can present this way 3, 1, 2

Initial Diagnostic Workup

History and Physical Examination

Document these critical risk factors for colorectal cancer 6:

• Age (risk increases significantly over 50 years) 3, 6
• Family history of colorectal cancer 6
• Personal history of polyps or inflammatory bowel disease 6
• Duration and character of bleeding 6

Perform digital rectal examination on all patients to assess for anorectal pathology, blood presence, and masses 3, 7

Laboratory Tests

Order the following blood tests immediately 3, 2:

• Complete blood count (hemoglobin/hematocrit) 3, 2
• Coagulation studies (PT/INR, PTT) 3, 2
• Blood urea nitrogen and creatinine 3
• Blood type and cross-match for patients with severe bleeding or hemodynamic instability 3

Management Algorithm Based on Hemodynamic Status

For Hemodynamically Unstable Patients (Shock Index >1)

1. Initiate aggressive resuscitation with two large-bore IV catheters and crystalloid fluids 1, 2

2. Transfuse blood products using these thresholds 1, 2:

   • Hemoglobin <7 g/dL (target 7-9 g/dL) for patients without cardiovascular disease 1, 2
   • Hemoglobin <8 g/dL (target ≥10 g/dL) for patients with cardiovascular disease 1, 2

3. Perform CT angiography immediately to localize bleeding before any other intervention 3, 1, 2

4. Proceed to catheter angiography with embolization within 60 minutes if CTA is positive and interventional radiology is available 24/7 1, 2

5. Consider upper endoscopy immediately if no source identified on CTA, as UGIB can present with bright red rectal bleeding 3, 1

6. Proceed directly to surgery if patient remains unstable despite aggressive resuscitation (non-responder) 2

For Hemodynamically Stable Patients

1. Perform anorectal examination with anoscopy, proctoscopy, or flexible sigmoidoscopy with retroflexion to evaluate for hemorrhoids, fissures, and low rectal pathology 3, 7

2. Order colonoscopy based on Oakland score 3:

   • Oakland score ≤8: Outpatient colonoscopy within 2 weeks (especially for patients >50 years) 3
   • Oakland score >8: Inpatient colonoscopy on next available list 3

3. Perform colonoscopy within 24 hours after adequate bowel preparation for patients admitted with major bleeding 3, 2

4. If colonoscopy is negative and bleeding persists, consider 3:

   • Video capsule endoscopy (ideally within 48 hours, diagnostic yield 50-72% for obscure bleeding) 3
   • Repeat CTA if bleeding becomes more brisk 3
   • Nuclear medicine studies for intermittent or slow bleeding 3

Management of Anticoagulation and Antiplatelet Therapy

For Patients on Warfarin

• Interrupt warfarin immediately for unstable GI hemorrhage 1, 2
• Reverse with prothrombin complex concentrate and vitamin K 1, 2
• Restart warfarin at 7 days after hemorrhage for patients with low thrombotic risk 1, 2
• Consider low molecular weight heparin at 48 hours for patients with high thrombotic risk 1

For Patients on Aspirin

• Permanently discontinue aspirin if used for primary prophylaxis 1
• Do not routinely stop aspirin for secondary prevention; if stopped, restart as soon as hemostasis is achieved 1

For Patients on Dual Antiplatelet Therapy

• Reinstate P2Y12 receptor antagonist within 5 days if stopped, to prevent thrombotic complications 1

Specific Management for Radiation Proctitis

For patients with radiation-induced rectal bleeding 3:

1. Investigate with flexible endoscopy to confirm telangiectasia 3
2. Optimize bowel function and stool consistency 3
3. If bleeding affects quality of life, start sucralfate enemas (2g in 30-50ml water, twice daily, retained as long as possible) 3
4. Consider definitive ablation with hyperbaric oxygen or endoscopic laser therapy if medical management fails 3

Avoid argon plasma coagulation in radiation proctitis due to serious complication rates of 7-26% in chronically ischemic tissues 3

Critical Pitfalls to Avoid

• Never assume hemorrhoids are the sole cause without full colonic evaluation in patients over 40, as 44% have serious pathology including cancer and polyps 4, 8
• Do not rely on symptoms alone to determine who needs investigation—symptoms are unreliable and change between initial presentation and colonoscopy 4
• Failure to consider upper GI source in hemodynamically unstable patients leads to delayed diagnosis and increased mortality 3, 1, 2
• Do not delay endoscopy beyond 24 hours in high-risk admitted patients 2
• Remember that mortality relates more to comorbidities than exsanguination (overall 3.4%, but 18% for inpatient-onset LGIB and 20% for patients requiring ≥4 units of blood) 1, 2

Imaging Considerations

Imaging is not routinely indicated for suspected hemorrhoids unless there is suspicion of concomitant disease such as abscess, inflammatory bowel disease, or neoplasm 3

For patients with renal impairment or contrast allergy requiring CTA, follow established Royal College of Radiologists guidelines for contrast administration 3