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Difficulty: MediumDiagnostic Workup and Test Sequencing

A 29-year-old woman, gravida 2, para 1, at 26 weeks gestation, comes to the emergency department due to sudden-onset shortness of breath and sharp, right-sided chest pain that worsens with deep inspiration. The symptoms began 2 hours ago. She also reports progressive swelling and discomfort in her left leg over the past 3 days. Her pregnancy has been uncomplicated, and she has no significant past medical history. She takes prenatal vitamins. Her temperature is 37.1 C (98.8 F), blood pressure is 112/70 mm Hg, pulse is 118/min, and respirations are 24/min. Pulse oximetry shows 94% on room air. Examination reveals clear lungs bilaterally. The cardiovascular examination is notable for tachycardia without murmurs. The left calf is visibly swollen, erythematous, and tender to palpation, with a circumference 4 cm greater than the right calf. Which of the following is the most appropriate next step in the diagnostic evaluation of this patient?

  1. Compression ultrasonography of the lower extremitiesAnswer
  2. B
    Computed tomography pulmonary angiography
  3. C
    Ventilation-perfusion lung scan
  4. D
    Measurement of serum D-dimer level
  5. E
    Chest radiography

Answer

Compression ultrasonography of the lower extremities
The correct answer is compression ultrasonography of the lower extremities. In pregnant patients who present with signs and symptoms of both pulmonary embolism and deep vein thrombosis, the safest and most appropriate initial diagnostic step is to evaluate the symptomatic leg with ultrasound. Confirming a deep vein thrombosis provides a definitive indication to initiate therapeutic anticoagulation, which is the exact same treatment required for a pulmonary embolism. This step-wise approach prevents the mother and fetus from being exposed to the ionizing radiation associated with chest radiography, computed tomography, or ventilation-perfusion scanning.

Step-by-Step Solution

1
Evaluate the clinical presentation and vital signs.
The patient presents with tachycardia, tachypnea, hypoxia, pleuritic chest pain, and a unilaterally swollen, tender leg.
To establish a high clinical suspicion for acute pulmonary embolism and concurrent deep vein thrombosis.
2
Consider the diagnostic constraints unique to this patient.
The patient is in her second trimester of pregnancy, meaning diagnostic algorithms must prioritize minimizing radiation exposure to the fetus.
To apply principles of radiation stewardship and patient safety.
3
Determine the optimal diagnostic sequence according to guidelines.
Guidelines dictate that pregnant patients with suspected pulmonary embolism and symptoms of deep vein thrombosis should first undergo compression ultrasonography of the symptomatic leg.
If the ultrasound is positive, therapeutic anticoagulation is initiated (which treats both conditions), safely avoiding the need for thoracic imaging such as CT or V/Q scan.

Key Concept

In pregnant patients with suspected pulmonary embolism and concurrent symptoms of deep vein thrombosis, bilateral or symptomatic-leg compression ultrasonography is the preferred initial diagnostic test to potentially avoid fetal radiation exposure.
Estimated Time:1m 0s
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Diagnostic Workup and Test Sequencing

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