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Difficulty: HardOrdering Imaging Studies

Match each clinical presentation to the single most appropriate initial or subsequent imaging modality. Consider patient-specific contraindications, hemodynamic status, and established diagnostic algorithms.

  • A nulliparous patient at 26 weeks gestation requiring further evaluation for worsening focal peritonitis and leukocytosis following an indeterminate right lower quadrant ultrasound.Magnetic resonance imaging (MRI) without gadolinium
  • Immediate evaluation for an individual with a non-MRI-compatible permanent pacemaker who rapidly developed profound paraparesis, saddle anesthesia, and urinary retention.Computed tomography (CT) myelography
  • Initial trauma bay management for an unrestrained driver with a rigid abdomen, tachycardia, and a sustained systolic blood pressure of 70 mm Hg70 \text{ mm Hg} following a high-velocity collision.Focused assessment with sonography for trauma (FAST)
  • Subsequent evaluation for a hospitalized individual with persistent fever, right upper quadrant pain radiating to the scapula, and leukocytosis, but an equivocal initial ultrasonography.Hepatobiliary iminodiacetic acid (HIDA) scan

Answer

The pregnant patient with an indeterminate ultrasound matches with MRI without gadolinium; the pacemaker patient with suspected cauda equina syndrome matches with CT myelography; the unstable trauma patient matches with a FAST scan; and the patient with an equivocal ultrasound for acute cholecystitis matches with a HIDA scan.
Each clinical scenario requires a specific modification to standard imaging protocols. Pregnancy dictates avoidance of ionizing radiation (MRI preferred over CT). Non-MRI-compatible implants block the use of magnetic resonance (CT myelography preferred over MRI). Hemodynamic instability restricts patient transport (bedside FAST preferred over CT). Equivocal anatomical imaging requires functional confirmation (HIDA preferred over repeat US or CT).

Step-by-Step Solution

1
Evaluate the pregnant patient with suspected appendicitis.
Identify the need for cross-sectional imaging without ionizing radiation.
Ultrasound was inconclusive, and CT carries fetal radiation risks, making MRI without contrast the safest definitive study.
2
Evaluate the patient with neurological deficits and a permanent pacemaker.
Identify the need for spinal visualization using an MRI alternative.
MRI is absolutely contraindicated due to the non-compatible implant, necessitating CT myelography to visualize the spinal cord and nerve roots.
3
Evaluate the hemodynamically unstable trauma patient.
Identify the need for immediate, bedside diagnostic testing.
Hemodynamic instability precludes safe transport to the radiology suite for a CT scan; FAST scan rapidly assesses for free intraperitoneal fluid.
4
Evaluate the patient with suspected acute cholecystitis.
Identify the need for functional biliary imaging.
Initial anatomical imaging (ultrasound) was equivocal, requiring a functional evaluation of cystic duct patency via cholescintigraphy (HIDA).

Key Concept

Selecting the optimal imaging modality based on diagnostic algorithms while adjusting for absolute contraindications and hemodynamic stability.
Estimated Time:1m 30s
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Ordering Imaging Studies

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