In a 66-year-old woman with four episodes of bright‑red, clot‑filled stools, orthostatic light‑headedness, tachycardia, anemia, elevated BUN, and impaired renal function, who has never had a colonoscopy and has two negative fecal immunochemical tests, what is the most likely cause of her symptoms?

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Upper Gastrointestinal Bleeding (UGIB) from a Peptic Ulcer

This patient most likely has an upper gastrointestinal source of bleeding, specifically a peptic ulcer, despite the presence of bright red blood per rectum. The combination of brisk rectal bleeding with hemodynamic instability (tachycardia, orthostatic symptoms), anemia, and a disproportionately elevated BUN-to-creatinine ratio strongly suggests UGIB rather than a lower GI source 1.

Key Clinical Indicators Pointing to UGIB

The elevated BUN (42) with creatinine of 1.86 creates a BUN:Cr ratio of approximately 23:1, which is significantly elevated and classic for upper GI bleeding. This occurs because:

  • Blood in the upper GI tract is digested and absorbed, increasing urea nitrogen
  • The brisk nature of bleeding with hemodynamic compromise (HR 106, orthostatic symptoms)
  • Anemia (Hgb 9.4) indicating significant blood loss

The British Society of Gastroenterology guidelines explicitly state that "brisk rectal bleeding and haemodynamic compromise" with "elevated blood urea/creatinine ratio" are findings suggestive of an upper GI source 1. Up to 11-15% of patients presenting with apparent lower GI bleeding are ultimately found to have an UGIB source 1.

Why the Negative Fecal Tests Are Misleading

The two negative fecal immunochemical tests (FIT) do not exclude acute bleeding:

  • FIT tests are designed for chronic, occult bleeding and colorectal cancer screening
  • They have poor sensitivity for acute hemorrhage
  • They cannot detect upper GI sources reliably
  • In acute bleeding scenarios, they are essentially irrelevant

Diagnostic Algorithm for This Patient

Given her shock index (HR/SBP) is likely ≥1 based on tachycardia and orthostatic symptoms:

  1. First-line investigation: CT angiography (CTA) if she remains unstable after initial resuscitation 1

    • CTA can localize bleeding in upper GI, small bowel, or lower GI tract
    • Sensitivity 79-95%, specificity 95-100%
    • No bowel preparation required
    • Rapidly accessible

  2. If patient stabilizes after resuscitation: Upper endoscopy (EGD) should be the first investigation 1

    • This directly visualizes the most likely source
    • Allows for therapeutic intervention

  3. If CTA is performed first and shows no source: Immediate upper endoscopy 1

Common Pitfall to Avoid

Do not proceed directly to colonoscopy based solely on the appearance of bright red blood. Research shows that even with bright red hematochezia, 20 of 217 patients (9%) had proximal colonic lesions beyond sigmoidoscope reach, and importantly, UGIB can present this way 2. The guideline emphasizes that "bright or dark red blood per rectum or blood mixed in with stool and haemodynamic instability may be a presentation of UGIB" 1.

Why Not Lower GI Sources?

While angiodysplasia is common in elderly patients and can be associated with chronic renal insufficiency 3, 4, this patient's presentation is too acute and severe. Angiodysplasia typically presents with:

  • Chronic intermittent bleeding or iron deficiency anemia
  • Less dramatic hemodynamic compromise
  • Normal BUN:Cr ratio

The shock index ≥1, elevated BUN:Cr ratio, and acute presentation with clots make UGIB far more likely than colonic angiodysplasia or other lower GI pathology.

References

4
Research

[Angiodysplasia of the small bowel: a possible cause of anemia even in mild chronic renal failure].

Giornale italiano di nefrologia : organo ufficiale della Societa italiana di nefrologia, 2005

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