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Difficulty: HardOrdering Imaging Studies

Match each patient's clinical presentation and specific risk factors with the most appropriate next step in diagnostic imaging.

  • A 68-year-old man with a non-MRI-compatible cardiac pacemaker who presents with new-onset bilateral lower extremity weakness, hyperreflexia, a sensory level at T10, and urinary retention.CT myelography of the spine
  • A 32-year-old woman at 14 weeks gestation who presents with fever, leukocytosis, and severe right lower quadrant abdominal pain; an initial graded compression ultrasound is non-diagnostic due to overlying bowel gas.MRI of the abdomen and pelvis without contrast
  • A 45-year-old man with Marfan syndrome who presents with sudden-onset, severe, tearing chest pain radiating to his back; his medical records document a history of anaphylactic shock following administration of iodinated contrast media.Transesophageal echocardiography (TEE)
  • A 72-year-old man who recently experienced a transient ischemic attack (TIA) and requires evaluation of the extracranial cervical vasculature; he has severe claustrophobia and an estimated glomerular filtration rate (eGFR) of 15 mL/min/1.73 m².Duplex ultrasonography of the carotid arteries

Answer

1. Spinal cord compression with pacemaker -> CT myelography of the spine; 2. Suspected appendicitis in pregnancy after non-diagnostic US -> MRI of the abdomen and pelvis without contrast; 3. Suspected aortic dissection with contrast allergy -> Transesophageal echocardiography (TEE); 4. Carotid evaluation with low eGFR and claustrophobia -> Duplex ultrasonography of the carotid arteries.
Each correct pairing successfully navigates patient-specific contraindications to standard imaging modalities. CT myelography circumvents the pacemaker contraindication for MRI. MRI abdomen without contrast avoids fetal radiation when ultrasound is inconclusive. TEE rapidly assesses the aorta without triggering an iodine allergy. Duplex ultrasound safely evaluates carotids in a claustrophobic patient with severe renal failure.

Step-by-Step Solution

1
Analyze the first presentation: spinal cord compression syndrome in a patient with a non-MRI-compatible pacemaker.
Identified the need to evaluate the spinal canal while avoiding the standard first-line MRI due to absolute contraindication.
MRI magnetic fields can disrupt pacemakers, necessitating an alternative like CT myelography.
2
Evaluate the second presentation: pregnant patient with suspected appendicitis and a non-diagnostic ultrasound.
Selected MRI without contrast as the next best step to avoid fetal radiation exposure.
CT carries a risk of teratogenicity and childhood malignancy, making non-contrast MRI the preferred second-line modality in pregnancy.
3
Assess the third presentation: Marfan syndrome patient with suspected aortic dissection and severe iodine allergy.
Chose TEE instead of the standard CTA.
CTA requires iodinated contrast, which could trigger a life-threatening anaphylactic reaction, making TEE the safest rapid diagnostic tool.
4
Review the fourth presentation: TIA patient needing carotid evaluation with an eGFR of 15 and severe claustrophobia.
Selected Duplex ultrasonography over CTA or MRA.
CTA risks contrast nephropathy, while MRA is limited by claustrophobia and the risk of gadolinium-induced nephrogenic systemic fibrosis. Ultrasound is safe and effective.

Key Concept

Selecting alternative diagnostic imaging modalities when first-line studies are contraindicated by patient-specific factors such as implants, pregnancy, allergies, or renal impairment.
Estimated Time:1m 30s
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Topics

Ordering Imaging Studies

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