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Difficulty: HardDiagnostic Workup and Test Sequencing

A 65-year-old man is evaluated in the intensive care unit for recurrent large-volume hematochezia. He originally presented to the emergency department 24 hours ago with bright red blood per rectum and hypotension. His medical history includes hypertension, hyperlipidemia, and coronary artery disease. Following initial resuscitation with intravenous crystalloids and two units of packed red blood cells, his vital signs normalized. A nasogastric lavage returned clear fluid with no blood or coffee-ground material. An urgent upper gastrointestinal endoscopy demonstrated a normal esophagus, stomach, and duodenum. Following rapid bowel preparation, a colonoscopy was performed which revealed scattered diverticula and fresh blood throughout the colon, but no active bleeding site could be identified.

While in the intensive care unit, the patient passes another large, bloody stool. His blood pressure drops to 95/65 mmHg and his heart rate increases to 118/min.

Which of the following is the most appropriate next step in the diagnostic workup?

  1. Computed tomography angiography of the abdomen and pelvisAnswer
  2. B
    Technetium-99m labeled red blood cell scintigraphy
  3. C
    Video capsule endoscopy
  4. D
    Magnetic resonance angiography of the mesenteric vessels
  5. E
    Immediate exploratory laparotomy

Answer

The most appropriate next step is computed tomography angiography of the abdomen and pelvis.
The correct answer identifies the optimal diagnostic sequence for an unstable patient with brisk lower gastrointestinal bleeding whose initial endoscopic evaluations were non-diagnostic. The patient is suffering from obscure overt gastrointestinal bleeding, highly suggestive of a small bowel source or a missed diverticular bleed due to poor visualization. Because he is having active, large-volume hemorrhage with recurrent hemodynamic instability, rapid and precise anatomic localization is paramount. Multidetector computed tomography angiography (CTA) of the abdomen and pelvis is the test of choice. CTA is fast, non-invasive, universally available in emergency settings, and can detect bleeding rates of 0.3 to 0.5 mL/min. It provides an exact anatomic roadmap that allows interventional radiologists to immediately perform targeted transcatheter arterial embolization.

Step-by-Step Solution

1
Evaluate the patient's clinical status and presentation.
The patient has recurrent, large-volume hematochezia causing hemodynamic instability (hypotension, tachycardia).
Identifying the acuity and severity of the bleeding dictates the urgency and type of diagnostic intervention.
2
Review the initial diagnostic workup.
Upper endoscopy ruled out an upper GI source. Colonoscopy showed fresh blood but failed to identify the active bleeding site.
Bleeding with negative upper and lower endoscopies is classified as obscure gastrointestinal bleeding, likely originating from the small bowel or a hidden colonic diverticulum.
3
Determine the optimal diagnostic test for localization.
Computed tomography angiography (CTA) is selected.
In the setting of brisk, active bleeding (>0.3-0.5 mL/min) with hemodynamic compromise, CTA provides rapid, highly accurate anatomic localization of the bleeding source, which is essential before proceeding to transcatheter embolization or targeted surgery.

Key Concept

In patients with obscure overt lower gastrointestinal bleeding who develop hemodynamic instability after negative endoscopic evaluations, computed tomography angiography (CTA) is the preferred next step in the diagnostic workup.
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Diagnostic Workup and Test Sequencing

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