What is the best initial step for a patient with massive lower GI bleeding and no blood in the NGT?

Management of Massive Lower GI Bleeding with Negative NGT

For a patient with massive lower GI bleeding and no blood in the nasogastric tube (NGT), CT angiography (CTA) should be the first-line diagnostic approach due to its high sensitivity (80-90%) for detecting active bleeding at rates as low as 0.3-1.0 mL/min. 1

Initial Assessment and Stratification

1. Hemodynamic Assessment

   • Calculate shock index (heart rate divided by systolic blood pressure)
   • Shock index >1 indicates unstable bleeding 2
   • Establish two large-bore IV access for fluid resuscitation

2. Risk Stratification

   • Apply Oakland score to categorize as major or minor bleeding 2
   • Score >8 points indicates major bleeding requiring hospital admission
   • Components include age, gender, previous LGIB admission, DRE findings, vital signs, and hemoglobin level

Diagnostic Algorithm for Massive Lower GI Bleeding

Step 1: Rule Out Upper GI Source

• Negative NGT aspirate suggests lower GI source but doesn't completely rule out upper GI bleeding
• Important note: 10-15% of severe hematochezia cases can still have upper GI sources despite negative NGT 1

Step 2: Diagnostic Imaging

• CT Angiography (CTA) is the recommended first-line diagnostic approach for massive lower GI bleeding 1
  • High sensitivity (80-90%) for detecting active bleeding
  • Can detect bleeding rates as low as 0.3-1.0 mL/min
  • Provides anatomical information to guide subsequent interventions

Step 3: Based on CTA Findings

• If CTA positive: Proceed to angiography for potential therapeutic intervention
• If CTA negative: Consider urgent colonoscopy after adequate bowel preparation

Rationale for CTA as First-Line Approach

1. Speed and Accessibility:

   • CTA can be performed rapidly in hemodynamically unstable patients
   • Does not require bowel preparation like colonoscopy

2. Diagnostic Yield:

   • Higher diagnostic yield for active bleeding compared to other modalities in the acute setting
   • Helps localize the bleeding site to guide subsequent interventions

3. Clinical Pathway:

   • Positive CTA can lead directly to therapeutic angiographic intervention
   • Negative CTA allows for more controlled colonoscopic evaluation

Important Caveats

• Timing is critical: Diagnostic yield decreases as bleeding slows or stops
• Bowel preparation challenges: Massive bleeding makes adequate bowel preparation for immediate colonoscopy difficult
• Angiography limitations: Standard angiography without prior CTA has lower sensitivity and may miss intermittent bleeding 3
• Provocative angiography: May be considered in recurrent bleeding with negative standard workup, but carries risks 4

Treatment Options Following Diagnosis

• Angiographic embolization: Effective for diverticular bleeding, angiodysplasia 5
• Endoscopic therapy: Options include clips, thermal therapy, or injection therapy once the source is identified
• Surgical intervention: Consider if bleeding persists despite other interventions, requiring >6 units of blood, or with recurrent severe bleeding 1

While both angiography and endoscopy are viable options, the massive nature of the bleeding, negative NGT, and likely poor visualization with immediate colonoscopy make CTA the most appropriate initial diagnostic step, potentially followed by therapeutic angiography if a bleeding source is identified.