Question

A patient presents with dyspnea and tachycardia 7 days after undergoing knee replacement surgery. Which investigation will confirm the diagnosis?

• A. V/Q ratio
• B. D-dimer
• C. Chest X-ray
• D. CT Pulmonary Angiography (CTPA)

Hint:

Postoperative dyspnea and tachycardia = suspect pulmonary embolism; confirm with CTPA.

Answer 1

The Correct Option is D

Step 1: Understanding the Question:
A post-operative patient (especially after major orthopedic surgery) presenting with sudden onset shortness of breath and high heart rate is suffering from a Pulmonary Embolism (PE) until proven otherwise.
Step 2: Detailed Explanation:

Risk Factors: Total knee replacement is a high-risk surgery for Venous Thromboembolism (VTE) due to venous stasis, local trauma, and post-op immobilization.

Diagnostic Standard: CT Pulmonary Angiography (CTPA) is the current first-line and "gold standard" investigation for the confirmation of PE. It allows direct visualization of the thrombus within the pulmonary arteries as filling defects.

D-Dimer Limitations: While a negative D-dimer can help "rule out" PE in low-risk patients, it is almost always elevated in a post-operative patient due to the recent surgery itself, making it non-specific and unhelpful in this case.

V/Q Scan: This is used when CTPA is contraindicated (e.g., severe renal failure or dye allergy) but is less accurate and less widely available than CT.

Chest X-ray: CXR is often normal in PE (the "classic" finding is a clear lung with clinical distress), but it is primarily used to rule out other causes of dyspnea like pneumonia or pneumothorax.

Step 3: Final Answer:
CT Pulmonary Angiography is the preferred imaging modality to definitively confirm the diagnosis of pulmonary embolism.