Today’s question will test your understanding of a foundational respiratory medicine concept.
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A 68-year-old woman presents to the emergency department with a sudden onset of shortness of breath, chest pain, and coughing up blood-streaked sputum. She had hip surgery ten days ago. Her vital signs are as follows: Pulse 110/minute, respiratory rate 24/minute, blood pressure 130/85 mmHg, temperature 98.4°F (36.9°C), and oxygen saturation 90% on room air. Laboratory results reveal elevated D-dimer levels. A computed tomography scan of the chest is performed. Which of the following would be expected in this patient?
A. A hypodense filling defect in a segmental pulmonary artery
B. A hyperdense filling defect in a segmental pulmonary artery
C. Bilateral wedge-shaped opacities in the lung peripheries
D. Consolidation in the lower lobes of both lungs
E. Diffuse ground-glass opacities throughout the lung fields
F. Multiple nodular opacities scattered throughout both lungs
G. Unilateral pleural effusion with atelectasis
Detailed Breakdown of Answers + Correct Answer Below ⏬
ANSWER + QUESTION BREAKDOWN
The MENTAL MODEL used to answer this question comes from our detailed test-taking skills masterclass (check it out if you want to boost your USMLE test-taking skills). Here’s how to think through this question:
Step 1. Read the last line to determine the actual question: “Which of the following (CT findings) would be expected in this patient?”
Step 2: Is this a first-, second-, or third-order question?
Answer: 2nd order. 1st: Diagnose the problem, and 2nd: Recognize which CT finding would be present in this scenario.
Step 3: Read the vignette carefully and ask yourself: “What imaging finding is expected in a patient with the condition I believe to be present?”
Step 4. Look at the answer choices and select the option most closely resembling your final thought from “Step 3” above.
GENERAL ANALYSIS
Based on the clinical presentation and findings, this 68-year-old woman is likely experiencing a pulmonary embolism (PE), especially considering her recent hip surgery, symptoms, and elevated D-dimer levels. In cases of PE, the most common imaging finding on a CT pulmonary angiography is a filling defect in the pulmonary arteries.
ANSWER CHOICES:
CHOICE A: A hypodense filling defect in a segmental pulmonary artery
Explanation: This describes the typical appearance of an embolus on CT pulmonary angiography, where the clot appears as a hypoattenuating (hypodense) area within the contrast-filled pulmonary artery. This is the classic finding for a pulmonary embolism on CT, confirming the presence of a clot obstructing blood flow.
CHOICE B: A hyperdense filling defect in a segmental pulmonary artery
Explanation: A hyperdense defect would not be typical for an acute embolus. Emboli appear hypodense compared to the surrounding contrast-enhanced blood.
CHOICE C: Bilateral wedge-shaped opacities in the lung peripheries
Explanation: These indicate pulmonary infarcts, which can occur secondary to PE but are not the direct finding of an embolus. While possible, this is not the primary finding for diagnosing PE.
CHOICE D: Consolidation in the lower lobes of both lungs
Explanation: Consolidation suggests pneumonia or other inflammatory processes. It does not directly indicate PE.
CHOICE E: Diffuse ground-glass opacities throughout the lung fields
Explanation: Ground-glass opacities can occur in various conditions, such as interstitial lung disease or infection. This finding is not specific to PE.
CHOICE F: Multiple nodular opacities scattered throughout both lungs
Explanation: Nodular opacities suggest metastatic disease or granulomatous infections. This finding is not associated with acute PE.
CHOICE G: Unilateral pleural effusion with atelectasis
Explanation: Pleural effusion and atelectasis can occur secondary to various conditions but are not diagnostic, are nonspecific, and not directly indicative of PE.
FINAL VERDICT…
In cases of suspected pulmonary embolism, CT pulmonary angiography is used to visualize clots within the pulmonary arteries. The classic finding is a hypodense filling defect within an opacified artery, indicating obstruction by an embolus. This finding aligns with the patient's clinical presentation and risk factors following recent surgery.
CORRECT ANSWER: A) A hypodense filling defect in a segmental pulmonary artery
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That’s it for question 73!
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