What are the immediate steps to take and potential causes if an adult patient presents with hematochezia (blood in the stool)?

Blood in the Stool: Immediate Management and Diagnostic Approach

When an adult patient presents with hematochezia, immediately assess hemodynamic stability through vital signs and shock index calculation (heart rate/systolic BP), then proceed with urgent colonoscopy within 24 hours for stable patients or CT angiography before endoscopy for unstable patients. 1, 2

Immediate Assessment and Resuscitation

Hemodynamic Evaluation

• Check vital signs immediately and calculate shock index (heart rate divided by systolic blood pressure) to determine bleeding severity—a shock index <1 defines hemodynamic stability 1, 3
• Obtain complete blood count, coagulation parameters (PT/INR, aPTT), serum electrolytes, BUN, and creatinine to evaluate the patient's condition 4, 1
• Perform blood typing and cross-matching if signs of severe bleeding are present (shock index >1, ongoing visible bleeding, or hemoglobin <7 g/dL) 4, 1

Resuscitation Protocol for Unstable Patients

• Initiate immediate IV fluid resuscitation and transfuse packed red blood cells to maintain hemoglobin >7 g/dL (use 9 g/dL threshold if massive bleeding or cardiovascular comorbidities present) 4, 3
• Maintain mean arterial pressure >65 mmHg while avoiding fluid overload 4
• Recognize that approximately 20% of patients requiring ≥4 units transfusion have significant mortality risk 3

Diagnostic Algorithm Based on Hemodynamic Status

For Hemodynamically Stable Patients (Shock Index <1)

• Perform digital rectal examination and anoscopy/proctoscopy first to identify common anorectal causes such as hemorrhoids, fissures, or masses 1, 5, 2
• Proceed with colonoscopy within 24 hours after adequate bowel preparation as the initial diagnostic procedure—this has a diagnostic yield of 42-90% and allows for both diagnosis and therapeutic intervention 1, 2
• Examine the rectum with retroflexion (J-maneuver) during colonoscopy to evaluate hemorrhoidal disease and low rectal pathology 1

For Hemodynamically Unstable Patients (Shock Index >1)

• Perform nasogastric tube aspiration or upper endoscopy first to exclude upper GI bleeding, as 11-14% of patients presenting with hematochezia have an upper GI source 1, 2, 6
• Obtain CT angiography as the first-line investigation before colonoscopy—CTA detects bleeding at rates as low as 0.3 mL/min and should not be delayed 1, 3, 2
• Proceed to immediate surgery if patient remains non-responsive to resuscitation 3

Common Causes by Age and Clinical Context

Most Likely Etiologies

• Diverticulosis (17%) and angiodysplasia (30%) are the most common causes in adults, with angiodysplasia particularly common in elderly patients, typically occurring in the cecum and proximal ascending colon 1, 7
• Duodenal ulcer (44%) and gastric ulcer (20%) are the most common causes when upper GI bleeding presents as hematochezia 6
• Hemorrhoids, polyps/cancer (11%), and focal ulcers (9%) account for other significant causes 7
• Approximately 6% of patients presenting with lower GI bleeding have underlying colorectal cancer, making timely investigation critical 1

Endoscopic Hemostasis and Therapeutic Interventions

When to Perform Therapeutic Endoscopy

• Provide endoscopic hemostasis therapy to patients with high-risk endoscopic stigmata including active bleeding, non-bleeding visible vessel, or adherent clot 2
• Therapeutic options include mechanical therapy (clips, band ligation), thermal therapy, injection therapy (epinephrine), or combination approaches 3, 2
• Consider repeat colonoscopy with endoscopic hemostasis for patients with evidence of recurrent bleeding 2

Escalation for Refractory Bleeding

• If endoscopic hemostasis fails, use a "step up" approach with radiological interventions (angiography with embolization) followed by surgical procedures if necessary 4
• Emergency visceral angiography has a 14% diagnostic yield but 9% complication rate, making it complementary to colonoscopy rather than first-line 7

Special Clinical Scenarios

Portal Hypertension with Anorectal Varices

• Temporarily suspend beta-blockers during acute bleeding and attempt endoscopic variceal ligation, band ligation, sclerotherapy, or EUS-guided glue injection if feasible 4
• Involve hepatology team early for multidisciplinary management and consider vasoactive drugs (terlipressin or octreotide) to reduce splanchnic blood flow 4
• Administer a short course of prophylactic antibiotics (strong recommendation) 4

Hemorrhoidal Bleeding

• Check vital signs, determine hemoglobin and hematocrit, and assess coagulation to evaluate severity 4
• Initiate non-operative management as first-line therapy with dietary and lifestyle changes (increased fiber and water intake) 4
• Administer flavonoids to relieve symptoms and consider topical muscle relaxants for thrombosed hemorrhoids 4

Critical Pitfalls to Avoid

• Do not delay CT angiography in unstable patients—it should be performed before endoscopy, not after 1, 3
• Do not assume a lower GI source without excluding upper GI bleeding, especially in patients with hemodynamic instability, as 11-14% have an upper GI source 2, 6
• Do not discharge patients with an Oakland score >8 (calculated from age, previous LGIB admission, blood on digital rectal exam, heart rate, systolic BP, and hemoglobin) without hospital admission and investigation 1
• Avoid NSAIDs in patients with a history of acute lower GI bleeding, particularly if secondary to diverticulosis or angiodysplasia 2
• Do not stop aspirin therapy in patients with established high-risk cardiovascular disease (secondary prophylaxis) in the setting of lower GI bleeding—the exact timing of resumption depends on bleeding severity and thromboembolic risk 2