What is the initial workup for a patient presenting with hematochezia (blood in stool)?

Initial Workup for Hematochezia (Blood in Stool)

For any patient presenting with hematochezia, immediately assess hemodynamic stability with vital signs, hemoglobin/hematocrit, and coagulation parameters, then proceed with risk stratification using the Oakland score to determine whether hospital admission or outpatient investigation is appropriate. 1, 2

Immediate Assessment and Risk Stratification

Hemodynamic Evaluation

• Check vital signs (heart rate, blood pressure), complete blood count with hemoglobin/hematocrit, and coagulation parameters (PT/INR, PTT) immediately upon presentation 2, 1
• For severe bleeding, perform blood typing and cross-matching to prepare for possible transfusion 1, 2
• Calculate the Oakland score using age, gender, previous lower GI bleeding history, digital rectal exam findings, heart rate, systolic blood pressure, and hemoglobin level 1

Oakland Score Interpretation

• Score ≤8 points: Minor self-terminating bleed—patient can be safely discharged for urgent outpatient investigation with colonoscopy within 2 weeks 1, 2
• Score >8 points: Major bleed—requires hospital admission for colonoscopy on the next available list 1
• Note that 6% of patients presenting with lower GI bleeding have underlying bowel cancer, making timely endoscopy critical, particularly in patients over 50 years 1

Diagnostic Algorithm Based on Hemodynamic Status

For Hemodynamically Unstable Patients (Shock Index >1, Requiring >5 Units Blood)

• CT angiography (CTA) is the first-line investigation, not endoscopy, as it detects bleeding at rates as low as 0.3 mL/min and localizes the source before intervention 2, 3
• Immediate resuscitation with IV fluids and blood products takes absolute priority, with a goal of maintaining hemoglobin above 7 g/dL 2
• If CTA shows active extravasation, proceed directly to transcatheter arteriography/embolization 3
• Critical pitfall: Up to 10-15% of apparent lower GI bleeding originates from an upper GI source, especially in patients with severe hematochezia and hypovolemia 2, 3

For Hemodynamically Stable Patients

Step 1: Direct Anorectal Inspection

• Perform anoscopy or proctoscopy first when bright red rectal bleeding is present, as benign anorectal conditions (hemorrhoids, fissures) account for 16.7% of diagnoses 1, 2
• Digital rectal examination must be performed in all patients to assess for blood and palpable masses 1
• Examination must permit identification of vascular abnormalities and Dieulafoy ulcers; if performing flexible sigmoidoscopy, use retroflexion (J-maneuver) to evaluate hemorrhoidal disease and low rectal pathology 1

Step 2: Consider Upper GI Source

• If the patient has severe hematochezia with hypovolemia, history of peptic ulcer disease, portal hypertension, or antiplatelet/anticoagulant use, perform nasogastric lavage and/or upper endoscopy first 2, 3
• If blood, clots, or coffee grounds-appearing material is present in NG aspirate, upper endoscopy must be performed before colonoscopy 2

Step 3: Colonoscopy

• Colonoscopy is the diagnostic procedure of choice for hemodynamically stable patients, with diagnostic yields of 42-90% 1, 2, 3
• Colonoscopy must be complete to the cecum and of high quality with adequate bowel preparation 1
• For patients with Oakland score >8 (major bleed), perform colonoscopy on the next available list during hospital admission 1
• For patients with Oakland score ≤8 (minor bleed), schedule outpatient colonoscopy within 2 weeks, particularly for those over 50 years or with alarm features 1, 2

Special Populations and Symptoms

High-Risk Symptoms Requiring Colonoscopy

• Hematochezia (hazard ratio 10.66 for early-onset colorectal cancer) 1
• Iron deficiency anemia (ferritin <15 ng/dL, hazard ratio 10.81) 1
• Unexplained weight loss ≥5 kg (>11 pounds) within 5 years (odds ratio 2.23) 1
• These three symptoms mandate diagnostic colonoscopy, not fecal immunochemical testing (FIT), as FIT delays diagnosis and is associated with increased risk of advanced-stage disease 1

Lower-Risk Symptoms (Individualized Approach)

• Abdominal pain and changes in bowel habits are common and non-specific; endoscopic evaluation is not recommended for all young adults without other alarming symptoms or colorectal cancer risk factors 1
• However, blood mixed with stool, change in bowel habit, and abdominal pain were significantly associated with serious disease in patients over 40 years (P < 0.001, P < 0.005, P < 0.025 respectively) 4

Critical Pitfalls to Avoid

Do Not Use FIT for Symptomatic Patients

• FIT is not recommended for symptomatic patients with high-risk features (hematochezia, unexplained iron deficiency anemia, unexplained weight loss) because a positive result still requires colonoscopy, leading to diagnostic delays 1
• Delays in obtaining colonoscopy are associated with increased risk of advanced-stage disease 1

Do Not Assume Hemorrhoids Are the Only Source

• Even if an anorectal source like hemorrhoids is identified, patients may have a more proximal source of bleeding requiring full colonoscopy to exclude, as 44.4% of patients over 40 with rectal bleeding have serious pathology (colorectal cancer, polyps ≥5mm, inflammatory bowel disease) 4
• The risk of colorectal cancer in patients with rectal bleeding ranges from 2.4-11%, making complete colonic evaluation essential 5

Do Not Perform Single-Sample FOBT During Office Visit

• A single sample FOBT with stool collected by digital rectal examination during an office visit has very poor sensitivity and false positives may result from DRE-related trauma 1

Inadequate Bowel Preparation

• Inadequate bowel preparation leads to poor colonoscopic visualization and missed lesions; ensure proper preparation before elective colonoscopy 3

Alternative Diagnostic Modalities

When Colonoscopy Is Inconclusive

• If colonoscopy does not identify a bleeding source and bleeding continues, consider radionuclide scanning with 99mTc-labeled RBCs, which can detect bleeding rates as low as 0.1 mL/min 3
• Consider small bowel evaluation with capsule endoscopy or enteroscopy if upper and lower GI sources are excluded 2

Role of Imaging

• CT scan, MRI, or endoanal ultrasound should only be performed if there is suspicion of concomitant anorectal diseases (sepsis/abscess, inflammatory bowel disease, neoplasm) 1