What is the initial workup for a patient presenting with fresh blood in their stool?

Initial Workup for Fresh Blood in Stool

Begin with immediate hemodynamic assessment using the shock index (heart rate divided by systolic blood pressure)—a value >1 defines instability and mandates urgent CT angiography rather than endoscopy, while stable patients (shock index <1) can proceed with risk stratification and colonoscopy. 1, 2, 3

Immediate Assessment (All Patients)

• Check vital signs immediately and calculate shock index to determine the entire diagnostic pathway 1, 4, 2
• Perform digital rectal examination to confirm blood presence and assess for anorectal sources 1, 3
• Obtain complete blood count with hemoglobin/hematocrit to quantify bleeding severity 1, 4, 3
• Check coagulation parameters (PT/INR, PTT) to identify coagulopathy 1, 4, 3
• Type and cross-match blood if hemoglobin <10 g/dL or patient appears unstable 1, 4

Hemodynamically Unstable Patients (Shock Index >1)

For unstable patients, CT angiography is the first-line investigation—not colonoscopy—as it can detect bleeding at rates as low as 0.3 mL/min and guides subsequent intervention. 4, 2, 5, 3

• Establish large-bore IV access (two lines minimum) and begin aggressive crystalloid resuscitation 2, 5
• Transfuse packed red blood cells to maintain hemoglobin >7 g/dL (target 7-9 g/dL), though consider 9 g/dL threshold given cardiovascular stress 4, 2, 5, 3
• Perform CT angiography immediately before any endoscopic intervention—CTA has 79-95% sensitivity and can identify sources throughout the entire GI tract without bowel preparation 4, 5, 3
• Always exclude upper GI source with upper endoscopy if CTA is negative, as 10-15% of severe hematochezia originates above the ligament of Treitz despite bright red blood per rectum 2, 5
• Proceed to angiography with embolization within 60 minutes if CTA shows active bleeding 2
• Consider immediate surgery if patient remains in hemorrhagic shock despite resuscitation—diagnostic laparotomy is mandatory when bleeding continues despite >6 units transfused 4, 5

Hemodynamically Stable Patients (Shock Index <1)

Use the Oakland score to stratify stable patients: scores ≤8 allow safe discharge for outpatient colonoscopy within 2 weeks, while scores >8 require hospital admission and inpatient evaluation. 1, 2, 3

Oakland Score Components:

• Age: <40 years (0 points), 40-69 years (1 point), ≥70 years (2 points) 1
• Male gender: 1 point 1
• Previous lower GI bleeding admission: 1 point 1
• Blood on digital rectal exam: 1 point 1
• Heart rate: <70 (0), 70-89 (1), 90-109 (2), ≥110 (3 points) 1
• Systolic BP: <90 (5), 90-119 (4), 120-129 (3), 130-159 (2), ≥160 (0 points) 1
• Hemoglobin: <70 g/L (22), 70-89 (17), 90-109 (13), 110-129 (8), 130-159 (4), ≥160 (0 points) 1

For Oakland Score ≤8 (Minor Bleeding):

• Discharge for outpatient colonoscopy within 2 weeks if patient is over 50 years old or has other cancer risk factors 1, 3
• No other indication for admission is required 1

For Oakland Score >8 (Major Bleeding):

• Admit to hospital for observation and inpatient workup 1, 2
• Perform colonoscopy during hospital stay after adequate bowel preparation—timing can be non-urgent as there is no high-quality evidence that emergency colonoscopy (within 24 hours) improves outcomes compared to elective inpatient colonoscopy 3
• Transfuse to maintain hemoglobin >7 g/dL (target 7-9 g/dL) using restrictive strategy, or >8 g/dL (target ≥10 g/dL) if cardiovascular disease present 2, 3

Anticoagulation Management

• Interrupt warfarin immediately at presentation with GI bleeding 4, 3
• Reverse coagulopathy with prothrombin complex concentrate and vitamin K if INR >1.5 and bleeding is severe 2, 3
• Temporarily withhold direct oral anticoagulants at presentation 3
• Continue aspirin if taken for secondary cardiovascular prevention—do not withhold 3
• Continue aspirin but consider temporarily interrupting P2Y12 inhibitor in patients on dual antiplatelet therapy, based on bleeding severity and ischemic risk 3

Critical Pitfalls to Avoid

• Never assume all rectal bleeding is from a lower GI source—up to 15% originates above the ligament of Treitz, especially with hemodynamic instability 2, 5
• Do not attempt colonoscopy in unstable patients—endoscopy requires hemodynamic stability and airway protection that unstable patients cannot safely tolerate 5
• Do not delay CT angiography in unstable patients—perform before endoscopy as it changes management 4, 5
• Do not delay surgery beyond aggressive resuscitation attempts—mortality increases significantly when surgery is delayed in patients requiring >6 units transfusion 4, 5

Special Considerations for Suspected Anorectal Varices

• Perform ano-proctoscopy or flexible sigmoidoscopy as first-line diagnostic tool 1
• Consider endoscopic ultrasound with color Doppler as second-line for deep rectal varices 1
• Involve hepatology specialist team early for multidisciplinary management and portal hypertension optimization 1