What is the approach to a patient presenting with bloody stool?

Approach to Bloody Stool

Immediate Assessment and Risk Stratification

All patients presenting with bloody stool require immediate hemodynamic assessment using shock index (heart rate/systolic BP), with a shock index >1 defining instability and determining the entire diagnostic and therapeutic pathway. 1

Initial Vital Signs and Laboratory Evaluation

• Check blood pressure, heart rate, and calculate shock index immediately upon presentation 1, 2
• Obtain hemoglobin/hematocrit and coagulation parameters (PT/INR, aPTT) to assess bleeding severity 1, 2
• Perform blood typing and cross-matching if severe bleeding is present or shock index >1 1, 2
• Conduct digital rectal examination to assess stool character and rule out anorectal pathology 1

Risk Score Application for Stable Patients

• Apply the Oakland score to stable patients: scores ≤8 points indicate minor self-terminating bleeds suitable for urgent outpatient investigation rather than admission 1, 3
• Patients with Oakland scores >8 points require hospital admission for colonoscopy 1

Hemodynamically Unstable Patients (Shock Index >1)

Immediate Resuscitation

• Initiate IV fluid resuscitation immediately to normalize blood pressure and heart rate 2
• Maintain hemoglobin >7 g/dL during resuscitation (consider >9 g/dL for massive bleeding or cardiovascular comorbidities) 2
• Maintain mean arterial pressure >65 mmHg while avoiding fluid overload 1, 2

Diagnostic Algorithm for Unstable Patients

• Perform CT angiography as the first-line investigation before endoscopy in hemodynamically unstable patients—this is the fastest and least invasive means to localize bleeding. 1, 2
• CT angiography can detect bleeding at rates as low as 0.3 mL/min and helps localize the source 2
• If CT angiography is positive, proceed to catheter angiography with embolization within 60 minutes in centers with 24/7 interventional radiology 1
• If CT angiography is negative, perform upper endoscopy immediately, as hemodynamic instability may indicate an upper GI source presenting with bright red rectal bleeding due to rapid transit 1, 2

Surgical Intervention

• Proceed to emergency laparotomy only after every effort has been made to localize bleeding radiologically and/or endoscopically, except under exceptional circumstances 1
• Immediate surgery is indicated for hemorrhagic shock non-responsive to resuscitation 2

Hemodynamically Stable Patients

Stepwise Diagnostic Approach

• Begin with anoscopy or proctoscopy to identify common anorectal causes such as hemorrhoids or anal fissures. 2
• Perform colonoscopy within 24 hours after adequate bowel preparation as the primary diagnostic procedure for stable patients with major bleeding 1, 2, 3
• Consider second-look upper endoscopy or push enteroscopy if initial evaluations were inadequate 4

Outpatient vs. Inpatient Management

• Discharge patients with minor self-terminating bleeds (Oakland score ≤8) for urgent outpatient colonoscopy if no other admission indications exist 1, 3
• Admit patients with major bleeds (Oakland score >8) for inpatient colonoscopy 1

Anticoagulation Management

Vitamin K Antagonists (Warfarin)

• Withhold vitamin K antagonists in major lower GI bleeding 3
• In hemodynamically unstable patients, administer IV vitamin K plus four-factor prothrombin complex concentrate (or fresh frozen plasma if PCC unavailable) 3
• Correct coagulopathy according to bleeding severity and thrombotic risk 3

Direct Oral Anticoagulants (DOACs)

• Temporarily withhold DOACs at presentation in patients with major lower GI bleeding 3

Antiplatelet Therapy

• Continue low-dose aspirin in patients taking it for secondary cardiovascular prevention; if withheld, resume within 5 days or earlier if hemostasis achieved. 3
• For dual antiplatelet therapy (aspirin plus P2Y12 inhibitor), continue aspirin and consult cardiology before discontinuing the P2Y12 inhibitor 3
• If P2Y12 inhibitor is interrupted, restart within 5 days based on ischemic risk 3

Transfusion Strategy

Patients Without Cardiovascular Disease

• Use restrictive transfusion strategy with hemoglobin threshold ≤7 g/dL prompting transfusion 3
• Target post-transfusion hemoglobin of 7-9 g/dL 3

Patients With Cardiovascular Disease

• Use more liberal transfusion strategy with hemoglobin threshold ≤8 g/dL prompting transfusion 3
• Target post-transfusion hemoglobin ≥10 g/dL 3

Special Clinical Scenarios

Anorectal Varices

• Perform ano-proctoscopy or flexible sigmoidoscopy as first-line diagnostic tool 1
• Maintain Hb >7 g/dL and mean arterial pressure >65 mmHg during resuscitation 1
• Administer short course of prophylactic antibiotics 2
• Consider vasoactive drugs (terlipressin or octreotide) to reduce portal pressure 2
• Use endoscopic variceal ligation, band ligation, sclerotherapy, or EUS-guided glue injection for hemostasis 1

Inflammatory Bowel Disease

• Perform sigmoidoscopy and esophagogastroduodenoscopy first in stable IBD patients with GI bleeding 2
• Proceed to emergency surgery (subtotal colectomy with ileostomy) in hemodynamically unstable patients with acute severe ulcerative colitis and massive hemorrhage 2
• Do not delay surgery in critically ill patients with toxic megacolon 2, 5

Infectious Diarrhea with Bloody Stool

• Obtain detailed history including travel, food exposure, antibiotic use, day-care attendance, and immunocompromised status 1
• Assess for dysenteric symptoms: fever, tenesmus, blood/pus in stool 1
• Consider stool culture for Shigella, Salmonella, and Campylobacter if inflammatory features present 1

Age-Specific Considerations

• All patients over age 40 presenting with rectal bleeding should undergo colonoscopy or flexible sigmoidoscopy regardless of symptoms, as serious pathology (cancer, polyps ≥5mm, IBD) is detected in 44% of cases 6
• In neonates, cow's milk protein allergy (53%) and necrotizing enterocolitis (8%) are the most common causes, with only 1.7% requiring surgery 7

Critical Pitfalls to Avoid

• Do not delay CT angiography in unstable patients—it must be performed before endoscopy in hemodynamically compromised patients. 2
• Do not assume a lower GI source in unstable patients—upper GI bleeding can present with bright red rectal bleeding due to rapid transit. 2
• Do not delay surgery in critically ill patients with toxic megacolon or massive bleeding unresponsive to resuscitation 2, 5
• Do not rely solely on symptoms to determine who requires investigation in patients over 40—symptoms are unreliable and change between initial presentation and colonoscopy 6
• Do not routinely discontinue aspirin for secondary cardiovascular prevention without cardiology consultation 3