What is the diagnosis and treatment for a male patient with overt dark blood in 1/4 of his brown stool, who is asymptomatic?

Diagnosis and Management of Overt Dark Blood in Stool

Immediate Diagnosis

This asymptomatic male with dark blood comprising 1/4 of his stool unmixed with the brown portion most likely has a lower gastrointestinal source, with colorectal polyps (32% of cases) and colorectal cancer (19% of cases) being the most common causes, requiring colonoscopy within 2 weeks. 1, 2, 3

Clinical Significance and Risk Assessment

The presentation of dark blood unmixed with stool suggests:

• A distal colonic or rectal source rather than an anorectal condition, as hemorrhoids typically present with bright red blood on the surface of stool or on toilet paper 1
• Serious pathology is detected in 44.4% of patients over age 40 presenting with rectal bleeding, including colorectal cancer (8%), polyps ≥5mm (17%), and inflammatory bowel disease (11%) 2
• The unmixed nature of the blood is a significant finding, as blood mixed with stool is significantly associated with serious disease (P < 0.001) 2

Risk Stratification

Calculate the Oakland score to determine urgency 4, 1:

• If Oakland score ≤8 points: Patient can be managed as outpatient with colonoscopy within 2 weeks 5, 1
• If Oakland score >8 points: Requires hospital admission for inpatient colonoscopy on next available list 5, 4

Key Oakland score variables include age, gender, previous lower GI bleeding history, heart rate, blood pressure, hemoglobin level, and presence of blood on digital rectal exam 1

Diagnostic Workup

Immediate Assessment

• Perform digital rectal examination immediately to assess for blood in the rectal vault and identify obvious anorectal pathology 1
• Check hemoglobin, complete blood count, and assess hemodynamic stability (heart rate, blood pressure) 4
• Calculate shock index (heart rate/systolic BP); if >1, this indicates critical instability requiring different management 5, 6

Definitive Investigation

Colonoscopy is the definitive diagnostic test and must include assessment of the anal canal and rectum using proctoscopy, rigid sigmoidoscopy, or flexible endoscopic examination with retroflexion (J-maneuver). 5, 1

Timing of colonoscopy:

• Within 2 weeks for patients over 50 with unexplained rectal bleeding, as 6% have underlying bowel cancer 5, 1
• On next available list (within 24 hours) if patient requires hospital admission based on Oakland score or clinical instability 5, 4
• Adequate bowel preparation with polyethylene glycol solution is essential for optimal mucosal visualization and diagnostic yield 5, 4

Upper GI Evaluation

Upper GI endoscopy is NOT routinely indicated in this asymptomatic patient unless risk factors are present, though 11-15% of presumed lower GI bleeds originate from the upper GI tract 1

Consider upper endoscopy only if:

• Hemodynamic compromise develops 5, 1
• Elevated BUN/creatinine ratio 5
• History of peptic ulcer disease or portal hypertension 5
• Use of antiplatelet drugs or anticoagulants 5

Prescription and Management

For Low-Risk Outpatient (Oakland Score ≤8)

• Discharge with urgent outpatient colonoscopy scheduled within 2 weeks 5, 1
• Prescribe polyethylene glycol bowel preparation to be taken before colonoscopy 5
• Provide clear instructions to return immediately if bleeding increases, hemodynamic symptoms develop, or abdominal pain occurs 5

If Anorectal Pathology Confirmed

• Conservative management with fiber supplementation, adequate hydration, and stool softeners for confirmed hemorrhoids or fissures 1
• Referral to colorectal surgery if medical management fails 1

Critical Pitfalls to Avoid

Do not assume hemorrhoids or diverticular disease are the source without colonoscopy, as coexistence of internal hemorrhoids or diverticular disease with neoplastic colonic lesions is common 3

Symptoms are unreliable for risk stratification - patients' descriptions of bleeding are somewhat unreliable, and symptoms change significantly between initial presentation and colonoscopy 2

Do not rely on normal rectal examination to exclude significant pathology - abnormal findings at colonoscopy occur in 52% of patients with normal rectal exams 7

All patients over age 40 with rectal bleeding require full colonic evaluation regardless of rectal examination findings, as 16 of 18 lesions found on colonoscopy in one series were in the left colon despite varying rectal exam findings 8