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Difficulty: MediumOrdering Imaging Studies

A 9-year-old boy is brought to the emergency department by his parents due to abdominal pain that began yesterday. The pain initially started around his umbilicus but has since migrated to the right lower quadrant. He has had one episode of nonbilious vomiting and has refused to eat since yesterday morning. His temperature is 38.3∘C38.3^\circ\text{C} (101.0∘F101.0^\circ\text{F}), blood pressure is 105/65 mm Hg105/65\text{ mm Hg}, pulse is 110/min110\text{/min}, and respiratory rate is 18/min18\text{/min}. Physical examination reveals localized tenderness halfway between the anterior superior iliac spine and the umbilicus, along with involuntary guarding. Laboratory studies demonstrate a leukocyte count of 14,500/mm314,500/\text{mm}^3 with 82% neutrophils. Which of the following is the most appropriate initial imaging modality to evaluate this patient's condition?

  1. Graded compression ultrasonography of the right lower quadrantAnswer
  2. B
    Contrast-enhanced computed tomography of the abdomen and pelvis
  3. C
    Upright and supine abdominal radiography
  4. D
    Abdominopelvic magnetic resonance imaging without contrast
  5. E
    Hepatobiliary iminodiacetic acid scintigraphy

Answer

Graded compression ultrasonography of the right lower quadrant is the most appropriate initial imaging study.
The correct answer is graded compression ultrasonography. Acute appendicitis classically presents with periumbilical pain migrating to the right lower quadrant, anorexia, nausea, fever, and focal tenderness. In pediatric and pregnant patients, ultrasonography is the initial imaging modality of choice. It is highly specific and avoids the ionizing radiation associated with a CT scan. If the ultrasound appendix cannot be visualized or the results are equivocal, further imaging (such as an MRI or a CT scan with intravenous contrast) may then be performed.

Step-by-Step Solution

1
Analyze the clinical presentation.
The patient has classic signs of acute appendicitis: migratory periumbilical to right lower quadrant pain, anorexia, fever, focal tenderness at McBurney's point, and leukocytosis with a left shift.
Establishing the most likely diagnosis guides the selection of the appropriate confirmatory test.
2
Consider the patient demographic and associated imaging risks.
The patient is a 9-year-old child. Pediatric patients are highly vulnerable to the long-term oncologic risks associated with ionizing radiation from computed tomography.
Age-specific guidelines mandate minimizing radiation exposure whenever a safer, diagnostically acceptable alternative exists.
3
Determine the optimal imaging sequence.
Graded compression ultrasonography is selected as the initial modality.
Ultrasonography provides a definitive diagnosis in most pediatric cases of appendicitis without radiation exposure. If the ultrasound is nondiagnostic or equivocal, subsequent imaging with CT or MRI can then be justified.

Key Concept

In pediatric patients with suspected acute appendicitis, graded compression ultrasonography is the initial imaging modality of choice to prevent unnecessary exposure to ionizing radiation.
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Ordering Imaging Studies

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