What is the approach to a patient with lower gastrointestinal (GI) bleeding, including history taking and management, considering factors such as age, underlying medical conditions, and medications like nonsteroidal anti-inflammatory drugs (NSAIDs) and anticoagulants?

Approach to Lower Gastrointestinal Bleeding

Immediate Hemodynamic Assessment

Calculate the shock index (heart rate ÷ systolic blood pressure) immediately upon patient presentation—a value >1 indicates hemodynamic instability and mandates emergency intervention with CT angiography rather than colonoscopy. 1, 2

• Check vital signs including blood pressure, heart rate, and assess for orthostatic changes to evaluate hemodynamic stability 2
• Obtain hemoglobin/hematocrit levels and coagulation parameters urgently 1, 2
• Assess for signs of hemodynamic compromise including pallor, tachycardia, hypotension, or syncope 2
• Patients requiring >2 units of packed red blood cells or showing hematocrit decrease ≥6% merit ICU admission 2, 3

Critical History Taking Elements

Age-Related Risk Stratification

Advanced age is the strongest risk factor for lower GI bleeding, with diverticulosis and angiodysplasia increasing dramatically in patients over 60-70 years. 4

• In patients >70 years: diverticulosis (21-41% of cases) and angiodysplasia (3-40% of cases) are the dominant causes 4
• In younger patients (<40 years): inflammatory bowel disease, infectious colitis, and benign anorectal conditions are more likely 5, 4

Medication History (Critical Risk Factors)

NSAID use is a critical risk factor that must be elicited in the medication history. 4

• Document all NSAIDs (diclofenac, ibuprofen), antiplatelet agents (aspirin, clopidogrel, prasugrel), and anticoagulants (warfarin, heparin, DOACs) 6
• Combination antiplatelet therapy or combined platelet inhibitor with anticoagulants dramatically increases bleeding risk compared to monotherapy 6
• Patients on DOACs should have these interrupted immediately at presentation 5
• For life-threatening hemorrhage on DOACs, consider idarucizumab (for dabigatran) or andexanet (for anti-factor Xa inhibitors) 5

Bleeding Characteristics

• Hematochezia with hemodynamic instability may indicate an upper GI source and warrants upper endoscopy first 3
• Painless bleeding characteristically suggests diverticulosis 4
• Chronic, intermittent bleeding suggests colorectal malignancy/polyps (6-27% of cases) rather than acute massive hemorrhage 4

Associated Symptoms

• Abdominal pain, weight loss, fever, vomiting, or partial intestinal obstruction suggest inflammatory, infectious, or malignant lesions 2
• Ask specifically about last bowel movement and passage of flatus to assess for bowel obstruction 2
• History of previous abdominal surgery has 85% sensitivity and 78% specificity for adhesive small bowel obstruction 2
• Inquire about chronic constipation (suggesting possible volvulus) and previous diverticulitis episodes 2

Comorbidities

• Identify significant cardiac disease, liver disease, and portal hypertension 5
• Portal hypertension can cause lower GI bleeding through anorectal varices or obscure ectopic varices in the small or large bowel 4
• Prognosis in patients with liver disease is related to severity of liver disease rather than magnitude of hemorrhage 5

Physical Examination Priorities

Digital rectal examination is mandatory to exclude anorectal pathology, confirm stool appearance, and palpate for rectal masses—approximately 40% of rectal carcinomas are palpable. 4, 2

• Perform careful cardiac, pulmonary, and abdominal examinations looking specifically for peritoneal signs, distension, or localized tenderness 2
• Assess for signs of bowel obstruction including abdominal distension, high-pitched bowel sounds, or absence of bowel sounds 2
• Never attribute rectal bleeding to hemorrhoids without complete colonic evaluation, especially in elderly patients—this leads to missed malignancies 2

Initial Resuscitation

Initiate IV fluid resuscitation immediately with two large bore venous cannulae in the anticubital fossae for hemodynamically compromised patients. 5

• Infuse normal saline to achieve falling pulse rate, rising blood pressure, and adequate urine output (>30 ml/h) 5
• Transfuse to maintain hemoglobin >7 g/dL (or >9 g/dL in patients with cardiovascular disease or massive bleeding) 4, 1
• Correct coagulopathy if INR ≥1.5 with fresh frozen plasma and vitamin K—INR ≥1.5 independently predicts severe diverticular hemorrhage 4, 1
• Correct thrombocytopenia (<50,000/µL) with platelets 2
• Maintain mean arterial pressure >65 mmHg while avoiding fluid overload 1

Diagnostic Algorithm

For Hemodynamically Unstable Patients (Shock Index >1)

CT angiography is the preferred diagnostic modality for unstable patients, providing the fastest and least invasive means to localize bleeding before planning endoscopic or radiological therapy, with sensitivity of 85-90%, specificity of 92%, and accuracy of 94-95%. 1

• Modern multidetector CT can detect bleeding rates as low as 0.1 mL/min 1
• CTA is preferred over colonoscopy in unstable patients because it can localize bleeding from upper GI tract, small bowel, or colon, is widely available, rapidly accessible, and requires no bowel preparation 1
• Consider urgent angiography with embolization or even surgery if persistent instability despite aggressive resuscitation 2, 3

For Hemodynamically Stable Patients

Use the Oakland score for risk stratification in stable patients—a score >8 indicates major bleeding requiring hospital admission and colonoscopy within 24 hours. 1

• Colonoscopy after adequate bowel preparation is the diagnostic and therapeutic procedure of choice for stable acute lower GI bleeding 1, 3
• Colonoscopy should be performed within 24 hours of patient presentation after adequate colon preparation 3
• Endoscopic hemostasis therapy should be provided to patients with high-risk endoscopic stigmata including active bleeding, non-bleeding visible vessel, or adherent clot 3
• The presence of endoscopic stigmata of recent bleeding (visible vessel or adherent clot) is a reliable marker of severe diverticular hemorrhage 5

Prognosis and Natural History

Approximately 75-90% of diverticular bleeding episodes stop spontaneously, especially in patients requiring <4 units of blood transfusion over 24 hours. 4

• Lower GI bleeding generally has spontaneous cessation in 80% of cases with mortality of 2-4%, which is less severe than upper GI bleeding 7
• The presence of a clean-based ulcer within a diverticulum may indicate low risk of recurrent hemorrhage and permit early discharge 5

Critical Pitfalls to Avoid

• Do not assume all bright red rectal bleeding is from a lower GI source; upper GI bleeding can present this way with brisk bleeding 2
• The combination of obstructive symptoms (vomiting, difficulty eating) with rectal bleeding in an elderly patient should raise immediate concern for malignancy until proven otherwise 2
• Elderly patients are at higher risk of endoscopy complications (0.24-4.9% vs 0.03-0.13% in younger patients), with cardiopulmonary events accounting for >50% of complications 2
• Patients with established high-risk cardiovascular disease should not stop aspirin therapy (secondary prophylaxis) in the setting of lower GI bleeding—the timing of restarting depends on severity of bleeding, adequacy of hemostasis, and risk of thromboembolic event 3

Disposition

• Mild/moderate bleed (normal pulse/BP, hemoglobin >100 g/l, age <60, insignificant comorbidity): admit to general medical ward with hourly vital signs, endoscopy on next available list 5
• Severe bleed (age >60, pulse >100, systolic BP <100 mm Hg, hemoglobin <100 g/l, significant comorbidities): admit with close monitoring, urinary catheter, continuous automated vital signs monitoring, endoscopy after hemodynamic stabilization 5