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Difficulty: MediumOrdering Imaging Studies

For each of the described clinical scenarios, select the single most appropriate initial diagnostic imaging modality to establish the diagnosis.

  • A 30-year-old pregnant woman at 26 weeks gestation presents with acute-onset tachycardia and shortness of breath. Her chest radiograph is normal, and she has no clinical signs of deep vein thrombosis.Bilateral lower extremity compression ultrasonography
  • A 68-year-old male with a non-MRI-compatible cardiac pacemaker and a history of intravenous drug use presents with a new-onset fever, severe focal back pain, and progressive lower extremity weakness.Computed tomography myelogram of the spine
  • A 45-year-old female presents with severe, episodic right-sided flank pain that radiates to her labia, accompanied by nausea and microscopic hematuria.Non-contrast computed tomography of the abdomen and pelvis
  • A 35-year-old male is evaluated after a high-speed motorcycle crash. He complains of midline neck pain but is fully alert with a Glasgow Coma Scale score of 15 and has no focal neurologic deficits.Non-contrast computed tomography of the cervical spine

Answer

Match the pregnant patient with suspected pulmonary embolism to lower extremity compression ultrasound; the patient with a pacemaker and suspected epidural abscess to CT myelogram; the patient with suspected nephrolithiasis to non-contrast CT of the abdomen/pelvis; and the trauma patient with neck pain to non-contrast CT of the cervical spine.
Each imaging modality is chosen based on evidence-based guidelines that account for the suspected diagnosis and any specific patient contraindications. Lower extremity ultrasound prevents unnecessary radiation in pregnancy; CT myelogram circumvents MRI contraindications in pacemaker patients; non-contrast CT abdomen/pelvis optimally visualizes renal stones; and non-contrast CT cervical spine provides definitive, high-resolution trauma evaluation.

Step-by-Step Solution

1
Evaluate the pregnant patient presenting with possible pulmonary embolism.
Identify the need to minimize radiation exposure.
Lower extremity ultrasound can diagnose a deep vein thrombosis, which is treated identically to a pulmonary embolism, safely sparing the patient from chest imaging.
2
Evaluate the patient with suspected spinal cord compression or epidural abscess.
Identify the absolute contraindication to magnetic resonance imaging.
The patient has a non-compatible pacemaker, requiring an alternative modality like CT myelogram to visualize the spinal canal.
3
Evaluate the patient with colicky flank pain and hematuria.
Recognize classic symptoms of nephrolithiasis.
Non-contrast CT is the gold standard and most appropriate initial test for identifying urinary tract stones.
4
Evaluate the patient involved in blunt trauma complaining of neck pain.
Apply cervical spine imaging guidelines.
High-risk mechanism and midline tenderness mandate imaging, and CT is superior to plain radiography in adults.

Key Concept

Appropriate selection of diagnostic imaging requires balancing modality accuracy against patient-specific contraindications, such as pregnancy or implanted medical devices.
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Ordering Imaging Studies

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