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Difficulty: MediumOrdering Imaging Studies

A 72-year-old man presents to the emergency department with sudden, severe abdominal pain that began 2 hours ago. He rates the pain as 10 on a 10-point scale and describes it as diffuse and unremitting. His medical history is significant for permanent atrial fibrillation, hypertension, and hyperlipidemia. He recently stopped taking his apixaban due to financial constraints. Vital signs are temperature 37.2°C (99.0°F), blood pressure 155/90 mmHg, heart rate 118/min and irregularly irregular, and respiratory rate 22/min. On physical examination, the abdomen is soft and non-distended; there is only mild diffuse tenderness to deep palpation, without rebound or guarding. Laboratory studies show a leukocyte count of 18,500/mm³ and a serum lactate of 4.2 mmol/L. Which of the following is the most appropriate initial imaging study to establish the diagnosis?

  1. Computed tomography angiography of the abdomen and pelvisAnswer
  2. B
    Invasive catheter mesenteric angiography
  3. C
    Computed tomography of the abdomen and pelvis without intravenous contrast
  4. D
    Abdominal duplex ultrasonography
  5. E
    Upright and supine plain abdominal radiographs

Answer

Computed tomography angiography of the abdomen and pelvis is the most appropriate initial imaging study.
The patient's presentation of severe abdominal pain out of proportion to physical examination findings, combined with an elevated lactate level and a history of unanticoagulated atrial fibrillation, is highly suspicious for acute embolic mesenteric ischemia. In this time-critical scenario, computed tomography angiography (CTA) of the abdomen and pelvis is the most appropriate initial diagnostic study. CTA is non-invasive, rapid, and highly sensitive and specific for identifying occlusions in the mesenteric vasculature (most commonly the superior mesenteric artery). It also allows for the assessment of bowel wall integrity (e.g., detecting pneumatosis intestinalis) and can identify alternative causes of an acute abdomen if ischemia is not present.

Step-by-Step Solution

1
Analyze the clinical presentation and risk factors.
The patient has severe abdominal pain out of proportion to physical exam findings (soft, mildly tender abdomen without peritonitis), elevated lactate, and a major risk factor (atrial fibrillation off anticoagulation).
Identifying the classic triad of sudden severe pain, lack of peritoneal signs, and embolic risk factors points strongly to acute mesenteric ischemia.
2
Determine the diagnostic requirements.
A rapid, highly sensitive and specific imaging modality is needed to evaluate the mesenteric arterial supply (primarily the superior mesenteric artery).
Acute mesenteric ischemia is a time-sensitive, life-threatening emergency requiring prompt vascular imaging to prevent bowel infarction.
3
Select the optimal imaging study.
Computed tomography (CT) angiography of the abdomen and pelvis.
CT angiography provides excellent visualization of the splanchnic vessels, can diagnose alternative pathologies, and is fast and non-invasive, making it the preferred initial diagnostic test.

Key Concept

Computed tomography angiography (CTA) is the initial imaging modality of choice for patients with high clinical suspicion of acute mesenteric ischemia.
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Ordering Imaging Studies

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