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Difficulty: Very hardDiagnostic Workup and Test Sequencing

A 68-year-old man presents to the clinic for a follow-up visit. Four days ago, he was evaluated in the emergency department for acute left flank pain and hematuria. A noncontrast computed tomography (CT) scan of the abdomen and pelvis demonstrated a 4-mm stone in the left ureter, which he has since passed. The radiologist's report also noted an incidental 14-mm, solitary, solid, noncalcified nodule in the posterior basal segment of the right lower lobe. The patient currently feels well and reports no chest pain, dyspnea, chronic cough, hemoptysis, or unintentional weight loss. His medical history is significant for hypertension and hyperlipidemia. He smoked one pack of cigarettes daily for 40 years but quit 3 years ago. There are no prior imaging studies available for comparison. Vital signs are within normal limits, and physical examination is unremarkable. Which of the following is the most appropriate next step in the diagnostic workup?

  1. Dedicated thin-slice computed tomography of the chestAnswer
  2. B
    Positron emission tomography-computed tomography scan
  3. C
    Image-guided transthoracic needle aspiration
  4. D
    Flexible bronchoscopy
  5. E
    Repeat computed tomography of the abdomen and pelvis in 3 months

Answer

The most appropriate next step is to obtain a dedicated thin-slice computed tomography (CT) of the chest.
This patient has a high-risk pulmonary nodule (14-mm, solid, in an older patient with a 40 pack-year smoking history). However, it was discovered incidentally on a CT scan of the abdomen and pelvis. Because abdominal CT scans have thicker slices at the lung bases, do not visualize the upper lung zones, and are prone to respiratory motion artifacts, they do not provide a complete thoracic evaluation. Therefore, before applying risk stratification guidelines (such as the Fleischner Society guidelines) to determine if a positron emission tomography (PET) scan or biopsy is needed, the entire thorax must be imaged with a dedicated, noncontrast, thin-slice CT of the chest. This will confirm the nodule's characteristics, measure its exact size, and screen for additional nodules or mediastinal lymphadenopathy.

Step-by-Step Solution

1
Identify the patient's risk factors for lung malignancy.
The patient is high-risk due to advanced age (68 years) and a significant smoking history (40 pack-years).
Risk stratification is essential for determining the pre-test probability of lung cancer.
2
Evaluate the clinical finding and its source.
A 14-mm solid pulmonary nodule was found incidentally on a noncontrast CT scan of the abdomen and pelvis.
The imaging modality on which the nodule was discovered dictates the immediate next step in the sequencing algorithm.
3
Determine the optimal diagnostic imaging sequence.
Because the nodule was identified on an incomplete thoracic study, a dedicated chest CT must be ordered before applying nodule management guidelines.
Abdominal CT scans do not visualize the entire lung parenchyma, use thicker slices at the lung bases, and are subject to motion artifacts, making them inadequate for full nodule characterization.

Key Concept

When a pulmonary nodule is incidentally discovered on an imaging study other than a dedicated chest CT (e.g., abdominal CT, spine MRI), the first step in the diagnostic workup is to obtain a dedicated thin-slice CT of the chest to fully characterize the nodule and evaluate the entire thorax.
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Diagnostic Workup and Test Sequencing

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