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Difficulty: MediumOrdering Imaging Studies

A 28-year-old female, currently at 14 weeks gestation, presents to the emergency department complaining of sudden-onset shortness of breath and right-sided pleuritic chest pain that began two hours ago. Her temperature is 37.2°C (99.0°F), blood pressure is 110/70 mm Hg, pulse is 115/min, and respiratory rate is 22/min. Oxygen saturation is 94% on room air. Physical examination reveals clear lungs to auscultation bilaterally. Her right calf is noticeably swollen, warm, and tender to palpation compared to the left. Which of the following is the most appropriate initial imaging study for this patient?

  1. A
    Computed tomography pulmonary angiography
  2. B
    Ventilation-perfusion (V/Q) scan
  3. Compression ultrasonography of the lower extremitiesAnswer
  4. D
    Chest radiography
  5. E
    Magnetic resonance angiography of the chest

Answer

Compression ultrasonography of the lower extremities
According to evidence-based guidelines for evaluating suspected pulmonary embolism in pregnancy, the initial diagnostic step depends on the presence of deep vein thrombosis (DVT) symptoms. Because this patient has a swollen and tender right calf, bilateral compression ultrasonography of the lower extremities is the most appropriate initial test. If the ultrasound is positive for DVT, the diagnosis of venous thromboembolism is established, and therapeutic anticoagulation is initiated. In this scenario, further imaging of the chest to confirm a pulmonary embolism is unnecessary, thereby sparing both the fetus and maternal breast tissue from potentially harmful ionizing radiation.

Step-by-Step Solution

1
Identify the patient's clinical presentation and physiological state.
The patient is a pregnant female (14 weeks gestation) presenting with classic signs of pulmonary embolism (dyspnea, pleuritic chest pain, tachycardia) and concurrent signs of deep vein thrombosis (unilateral calf swelling and tenderness).
Pregnancy requires specialized diagnostic algorithms for suspected venous thromboembolism to minimize fetal radiation exposure.
2
Determine the initial diagnostic approach for suspected pulmonary embolism in pregnancy with concurrent DVT symptoms.
Guidelines state that if a pregnant patient with suspected PE has signs or symptoms of DVT, bilateral compression ultrasonography of the lower extremities should be the initial test.
A positive ultrasound confirms DVT, which dictates the same treatment as a pulmonary embolism (therapeutic anticoagulation). This prevents the need for thoracic imaging (like CTPA or V/Q scan) and completely avoids ionizing radiation exposure to the fetus.

Key Concept

In pregnant patients with suspected pulmonary embolism and concurrent symptoms of deep vein thrombosis, compression ultrasonography of the lower extremities is the safest and most appropriate initial imaging study.
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Ordering Imaging Studies

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