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Difficulty: MediumDiagnostic Workup and Test Sequencing

A 29-year-old woman, gravida 2, para 1, at 28 weeks gestation, presents to the emergency department reporting a sudden onset of shortness of breath and right-sided chest pain that worsens with deep inspiration. She also notes that her right leg has felt "heavy" and painful since yesterday. Her pregnancy has been uncomplicated thus far, and she takes only prenatal vitamins. Vital signs show a temperature of 37.0°C (98.6°F), heart rate of 115/min, respiratory rate of 24/min, blood pressure of 118/76 mmHg, and oxygen saturation of 94% on room air. Physical examination reveals clear lungs bilaterally. The right calf is visibly enlarged, erythematous, and tender to palpation compared to the left. Which of the following is the most appropriate next step in the diagnostic workup?

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

Answer

Compression ultrasonography of the lower extremities
The correct answer is compression ultrasonography of the lower extremities. This patient's presentation is highly suspicious for a pulmonary embolism originating from a deep vein thrombosis. In pregnant patients, diagnostic sequencing must carefully balance accurate diagnosis with minimizing radiation exposure to the fetus and the maternal breast tissue. If a pregnant patient with suspected pulmonary embolism has signs or symptoms of deep vein thrombosis (such as unilateral leg swelling and pain), the most appropriate initial diagnostic step is bilateral compression ultrasonography. A positive finding confirms the diagnosis of venous thromboembolism and provides sufficient justification to initiate full therapeutic anticoagulation. Consequently, this eliminates the need to perform chest imaging (like a V/Q scan or CT pulmonary angiography), entirely sparing the patient and fetus from radiation.

Step-by-Step Solution

1
Analyze the clinical presentation.
The patient is pregnant and presents with classic signs of pulmonary embolism (pleuritic chest pain, tachycardia, dyspnea) along with concurrent signs of deep vein thrombosis (unilateral leg swelling, erythema, and tenderness).
Identifying both the suspected condition and the patient's unique physiological state (pregnancy) is critical to selecting safe and appropriate diagnostic modalities.
2
Determine the diagnostic algorithm for suspected pulmonary embolism in pregnancy.
Because the patient has symptoms of deep vein thrombosis, the algorithm prioritizes evaluating the leg first with compression ultrasonography.
If the compression ultrasound is positive for deep vein thrombosis, the diagnosis of venous thromboembolism is confirmed, and therapeutic anticoagulation can be initiated immediately without the need for further chest imaging, thereby completely avoiding radiation exposure.

Key Concept

Diagnostic sequencing for suspected pulmonary embolism in pregnancy prioritizes bilateral compression ultrasonography if deep vein thrombosis symptoms are present, to potentially confirm venous thromboembolism and avoid radiation exposure from chest imaging.
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Diagnostic Workup and Test Sequencing

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