What is the next best investigation with high diagnostic value for an elderly patient presenting with fresh blood per rectum, low hemoglobin (anemia), and a normal anorectal colonoscopy?

Upper GI Endoscopy (Option A)

In an elderly patient with fresh blood per rectum, significant anemia (Hb 8), and normal anorectal colonoscopy, upper GI endoscopy is the next investigation with highest diagnostic value.

Clinical Reasoning

This presentation represents a diagnostic dilemma where the bleeding source remains unidentified despite normal lower GI evaluation. The key to this case is recognizing that up to 15% of patients presenting with serious hematochezia actually have an upper gastrointestinal source 1. The combination of fresh blood per rectum with significant anemia (Hb 8) and hemodynamic evidence of bleeding (finger full of blood on digital rectal exam) suggests brisk bleeding that could originate from above the ligament of Treitz.

Why Upper Endoscopy Takes Priority

• British Society of Gastroenterology guidelines explicitly recommend that bright red rectal bleeding with hemodynamic instability may indicate an upper GI source, and senior clinical discussion should consider upper GI endoscopy before proceeding to other investigations 1

• In patients with high-risk features including hemoglobin drop and suspected ongoing bleeding, urgent colonoscopy PLUS upper endoscopy within 24 hours is recommended 1

• A randomized trial by Laine et al. demonstrated that 15% of patients with serious hematochezia (defined by hemodynamic changes, hemoglobin drop ≥1.5 g/dl, or transfusion requirement) had an upper GI source identified at upper endoscopy 1

• Even in selected patients with diverticulosis and hematochezia, up to 8% have an upper GI bleeding source 1

Why Other Options Are Less Appropriate

Tc-99 Radionuclide Scan (Option B)

• Radionuclide imaging should be considered only after repeat colonoscopy fails to identify the source 2
• Scintigraphy is indicated when endoscopic evaluation (both upper and lower) has been inconclusive 2
• The diagnostic sequence should prioritize endoscopy first, as it offers both diagnostic AND therapeutic capability 3

CT Scan (Option C)

• CT angiography is recommended primarily for hemodynamically unstable patients with shock index >1 AFTER initial resuscitation, or when active bleeding is suspected and endoscopy cannot be performed 1
• CTA should be performed in preference to colonoscopy in unstable patients, but this patient has already had colonoscopy, suggesting relative stability 1
• CT is a second-line investigation after endoscopic evaluation has been completed 1

Ultrasound (Option D)

• Ultrasound has no established role in the diagnostic algorithm for lower GI bleeding in this context 1
• EUS with color Doppler is mentioned only for suspected anorectal varices, which is not the clinical scenario here 1

Diagnostic Algorithm for This Patient

1. Perform upper GI endoscopy immediately to exclude peptic ulcer disease, esophageal varices, Dieulafoy lesions, or other upper GI sources 1

2. If upper endoscopy is negative, consider repeat colonoscopy with optimal bowel preparation, as the initial examination may have been suboptimal 2

3. If both upper and repeat lower endoscopy are negative, proceed to radionuclide scanning (Tc-99m labeled RBC scan) to detect active bleeding at rates of 0.1-0.5 mL/min 2

4. If scintigraphy is positive, perform urgent angiography within 1 hour for potential therapeutic intervention 2

Critical Clinical Pearls

• The presence of fresh blood does not reliably localize bleeding to the lower GI tract - brisk upper GI bleeding can present with hematochezia 1

• Risk factors suggesting upper GI source include: hemodynamic compromise, elevated blood urea/creatinine ratio, history of peptic ulcer disease, portal hypertension, and antiplatelet drug use 1

• Nasogastric tube placement is NOT routinely recommended as it does not reliably aid diagnosis, does not affect outcomes, and causes complications in up to one-third of patients 1

• The diagnostic yield of colonoscopy ranges from 72-86% in lower GI bleeding, meaning 14-28% of cases remain undiagnosed after initial colonoscopy 2

• Angiodysplasia accounts for up to 80% of obscure GI bleeding cases and is most common in the cecum and proximal ascending colon (54%) 2, but this would typically be visible on colonoscopy

Answer: A. Upper GI endoscopy 1