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A 65-year-old man is evaluated in the emergency department for sudden-onset right-sided pleuritic chest pain, dyspnea, and a mild dry cough that began 4 hours ago. He has a history of type 2 diabetes mellitus, hypertension, and chronic kidney disease. His current medications include lisinopril, amlodipine, and insulin glargine.

Vital signs are:
Temperature: 37.2°C (99.0°F)
Pulse: 112/min
Blood pressure: 135/85 mm Hg
Respiratory rate: 24/min
Oxygen saturation: 91% on room air

Physical examination reveals decreased breath sounds and dullness to percussion at the right lung base. Cardiovascular examination reveals tachycardia with a regular rhythm and no murmurs. The lower extremities exhibit trace bilateral pitting edema without localized swelling, erythema, or calf tenderness.

Laboratory studies show a serum creatinine of 2.9 mg/dL (baseline 2.7 mg/dL), with an estimated glomerular filtration rate (eGFR) of 22 mL/min/1.73 m222 \text{ mL/min/1.73 m}^2.

Chest radiography reveals a moderate right-sided pleural effusion and an area of consolidation in the right lower lobe. An electrocardiogram demonstrates sinus tachycardia. The physician maintains a high clinical suspicion for an acute pulmonary embolism.

Which of the following is the most appropriate next step in imaging?

  1. Bilateral lower extremity compression ultrasonographyCevap
  2. B
    Computed tomography pulmonary angiography
  3. C
    Ventilation-perfusion lung scan
  4. D
    Transthoracic echocardiography
  5. E
    Non-contrast computed tomography of the chest

Cevap

The most appropriate next step in imaging is bilateral lower extremity compression ultrasonography.
The correct response is bilateral lower extremity compression ultrasonography. This patient has a high clinical probability of an acute pulmonary embolism (PE). The gold-standard initial imaging test is computed tomography pulmonary angiography (CTPA). However, CTPA requires intravenous iodinated contrast, which is strongly avoided in patients with severe chronic kidney disease (eGFR < 30) due to the high risk of contrast-induced nephropathy. The standard alternative for patients who cannot receive contrast is a ventilation-perfusion (V/Q) scan. A critical limitation of the V/Q scan is that it requires a normal or near-normal chest radiograph. This patient's chest X-ray demonstrates a moderate pleural effusion and lower lobe consolidation. These abnormalities will cause matched ventilation and perfusion defects, rendering the V/Q scan indeterminate and diagnostically useless. When both CTPA and V/Q scans are contraindicated or expected to be non-diagnostic, bilateral lower extremity compression ultrasonography is the safest and most appropriate next step. Approximately 30-50% of patients with PE will have a detectable deep vein thrombosis (DVT) on ultrasound, even without classic leg symptoms. Identifying a DVT secures the diagnosis of venous thromboembolism (VTE) and provides a definitive indication for anticoagulation, effectively eliminating the need for complex or harmful chest imaging.

Adım Adım Çözüm

1
Assess the pre-test probability and standard imaging modality for the suspected diagnosis.
The patient's presentation (tachycardia, pleuritic chest pain, dyspnea) makes pulmonary embolism (PE) highly likely, which typically warrants computed tomography pulmonary angiography (CTPA).
Establishing the clinical likelihood determines the need for definitive vascular imaging.
2
Evaluate patient-specific contraindications for standard imaging.
CTPA is strongly relatively contraindicated due to the patient's severe chronic kidney disease (eGFR of 22 mL/min).
Intravenous iodinated contrast poses a high risk of contrast-induced nephropathy in severe renal impairment.
3
Identify the standard alternative imaging modality and assess its diagnostic feasibility.
Ventilation-perfusion (V/Q) scanning is the standard non-contrast alternative, but the patient's abnormal chest X-ray (consolidation and effusion) will likely render the V/Q scan non-diagnostic.
V/Q scans require a relatively clear radiograph to accurately interpret perfusion mismatches; matched defects from consolidations result in indeterminate findings.
4
Select the safest alternative diagnostic pathway to confirm venous thromboembolism.
Bilateral lower extremity compression ultrasonography should be performed, even without localized leg symptoms.
A positive ultrasound confirms deep vein thrombosis, providing a definitive indication for therapeutic anticoagulation and safely bypassing the need for contrast or radiation.

Anahtar Kavram

In hemodynamically stable patients with suspected pulmonary embolism who have contraindications to CTPA (e.g., severe CKD) and an abnormal chest X-ray (which renders a V/Q scan non-diagnostic), bilateral lower extremity compression ultrasonography is the preferred initial imaging step to confirm venous thromboembolism.
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