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Difficulty: HardDiagnostic Workup and Test Sequencing

A 29-year-old woman, G2P1, at 26 weeks gestation is brought to the emergency department due to a 2-hour history of sudden-onset shortness of breath and right-sided pleuritic chest pain. She has no significant past medical history and takes only prenatal vitamins. Her vital signs show a temperature of 37.2°C (99.0°F), blood pressure of 118/76 mmHg, heart rate of 112/min, respiratory rate of 24/min, and oxygen saturation of 94% on ambient air. Physical examination reveals clear lungs to auscultation bilaterally. The right calf is visibly swollen, erythematous, and tender to palpation compared to the left. Which of the following diagnostic studies should be ordered as the most appropriate initial steps in this patient's evaluation? (Select exactly 2)

  1. Compression ultrasonography of the lower extremitiesAnswer
  2. Chest radiographyAnswer
  3. C
    Computed tomography pulmonary angiography
  4. D
    Serum D-dimer assay
  5. E
    Ventilation-perfusion scan

Answer

Compression ultrasonography of the lower extremities and Chest radiography.
The correct diagnostic approach for suspected pulmonary embolism (PE) in pregnancy requires a specialized algorithm aimed at minimizing fetal radiation exposure. In a pregnant patient presenting with signs of both PE and deep vein thrombosis (DVT), the most appropriate initial concurrent steps are compression ultrasonography of the lower extremities and a chest radiograph. If the ultrasound is positive for DVT, the diagnosis of venous thromboembolism (VTE) is established, the patient is treated with therapeutic anticoagulation, and further pulmonary imaging (which carries a radiation risk) becomes unnecessary. A chest radiograph provides a low-radiation baseline evaluation to rule out other causes of acute dyspnea and is mandatorily required to triage the patient to either a V/Q scan (if normal) or a CT pulmonary angiography (if abnormal) in the event that the ultrasound is negative.

Step-by-Step Solution

1
Analyze the clinical presentation.
The patient is a pregnant woman presenting with acute dyspnea, tachycardia, pleuritic chest pain, and unilateral leg swelling, which is highly suspicious for a deep vein thrombosis (DVT) complicated by a pulmonary embolism (PE).
Establishing the pre-test probability and recognizing the specific patient population (pregnant) dictates the diagnostic algorithm.
2
Determine the optimal diagnostic imaging sequence to minimize fetal radiation.
In pregnant patients with signs of DVT, compression ultrasonography should be performed first.
If the ultrasound confirms a DVT, the patient is treated with therapeutic anticoagulation for VTE, and further thoracic imaging (CTPA or V/Q scan) can be safely avoided, sparing the fetus from unnecessary radiation.
3
Identify concurrent initial baseline investigations.
A chest radiograph is indicated concurrently in the initial evaluation.
A chest radiograph involves negligible fetal radiation. It is essential to rule out other causes of acute dyspnea (e.g., pneumothorax, pneumonia) and is required to decide between a V/Q scan (if CXR is normal) and a CTPA (if CXR is abnormal) should the ultrasound be negative.

Key Concept

In pregnant patients with suspected pulmonary embolism and symptoms of deep vein thrombosis, the initial diagnostic workup must include bilateral lower extremity compression ultrasonography (to potentially circumvent the need for thoracic imaging) and a baseline chest radiograph.
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Diagnostic Workup and Test Sequencing

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