What is the workup for rectal bleeding?

Workup for Rectal Bleeding

The workup for rectal bleeding should begin with risk stratification using tools like the Oakland score, followed by immediate endoscopic evaluation with anoscopy or proctoscopy, and colonoscopy for all patients over 40 years regardless of symptoms, as serious pathology is detected in up to 44% of cases. 1

Initial Assessment

• Perform a focused medical history and complete physical examination, including digital rectal examination, to rule out other causes of lower gastrointestinal bleeding 2
• Assess vital signs, hemoglobin, hematocrit, and coagulation parameters to evaluate bleeding severity 2
• For severe bleeding, obtain blood typing and cross-matching 2
• Risk stratify patients using tools like the Oakland score, where a score >8 indicates major bleeding requiring hospital admission 1

Diagnostic Algorithm Based on Bleeding Severity

Hemodynamically Unstable Patients

• For hemodynamically unstable patients or those with suspected active bleeding, perform CT angiography (CTA) first to rapidly localize the bleeding site 1
• Consider upper endoscopy to exclude an upper GI source of bleeding, especially in patients with hemodynamic instability 1

Hemodynamically Stable Patients

• Perform direct anorectal inspection with anoscopy or proctoscopy for patients with bright red rectal bleeding 1
• For patients over 40 years with minor self-terminating bleeding (Oakland score ≤8), arrange outpatient colonoscopy 1
• For patients over 50 years, colonoscopy should be performed within 2 weeks due to a 6% risk of underlying bowel cancer 1
• For patients with major bleeding (Oakland score >8), admit to hospital for colonoscopy on the next available list 1

Diagnostic Yield of Different Tests

• Anoscopy is effective for detecting hemorrhoids and other anorectal lesions but has limited visualization beyond the rectum 1
• Colonoscopy has a diagnostic yield of 42-90% for identifying the source of lower GI bleeding 1
• CT angiography has a sensitivity of 79-95% and specificity of 95-100% for active bleeding 1
• Endoscopic ultrasound (EUS) with color Doppler evaluation can be valuable as a second-line diagnostic tool for patients with suspected anorectal varices 2

Clinical Significance of Symptoms

• Blood mixed with stool significantly increases the probability of colorectal cancer (21%) 3
• Change in bowel habit and abdominal pain are also significantly associated with serious disease 4
• However, symptoms elicited at primary presentation may be less helpful as they can change significantly between initial consultation and colonoscopy 4

Common Causes of Rectal Bleeding

• Serious pathology (44.4% of cases): colorectal cancer, polyps (especially those ≥5mm), inflammatory bowel disease 4
• Benign conditions: hemorrhoids (most common), diverticular disease, anal fissures 4, 5
• Special considerations: anorectal varices, radiation proctitis, ischemic proctitis, infectious proctitis 5

Common Pitfalls to Avoid

• Attributing rectal bleeding solely to hemorrhoids without further investigation, as it may be a sign of more serious conditions including colorectal cancer 1
• Failing to exclude an upper GI source of bleeding, especially in patients with hemodynamic instability 1
• Relying solely on symptoms to determine who needs investigation, as symptoms are unreliable predictors of serious pathology 4, 3
• Delaying investigation in older patients - all patients over 40 years presenting with rectal bleeding should be referred for flexible sigmoidoscopy or colonoscopy regardless of symptoms 4

Special Considerations

• For patients with bleeding anorectal varices, a multidisciplinary approach is recommended, involving hepatology specialists 2
• In pregnant patients with bleeding anorectal varices and failed ultrasound detection of bleeding site, consider MRI angiography if available 2
• For patients with thrombosed hemorrhoids, the decision between non-operative management and early surgical excision should be based on local expertise and patient preference 2