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Difficulty: MediumOrdering Imaging Studies

A 3131-year-old primigravid woman at 2626 weeks gestation is evaluated in the emergency department for a 2424-hour history of progressively worsening right-sided abdominal pain. The pain initially began in the periumbilical region but has since localized to the right mid-to-upper abdomen. She reports nausea and one episode of vomiting. Her temperature is 38.1∘C38.1^\circ\text{C} (100.6∘F100.6^\circ\text{F}), blood pressure is 112/70 mmHg112/70\text{ mmHg}, pulse is 105/min105/\text{min}, and respirations are 16/min16/\text{min}. Physical examination reveals focal tenderness over the right lateral abdomen without rebound or guarding. Fetal heart tones are 145/min145/\text{min} and reactive. Laboratory studies show a leukocyte count of 15,200/mm315,200/\text{mm}^3 with 82%82\% neutrophils. Which of the following is the most appropriate initial imaging study to evaluate this patient's condition?

  1. Graded compression ultrasonography of the right abdomenAnswer
  2. B
    Magnetic resonance imaging of the abdomen and pelvis without intravenous contrast
  3. C
    Computed tomography of the abdomen and pelvis with intravenous contrast
  4. D
    Diagnostic laparoscopy
  5. E
    Upright and supine abdominal radiography

Answer

Graded compression ultrasonography of the right abdomen
The correct answer is graded compression ultrasonography. In pregnant patients with suspected acute appendicitis, ultrasound is the most appropriate initial imaging modality because it is safe, lacks ionizing radiation, and can often identify the inflamed appendix. Even though the enlarging uterus displaces the appendix superiorly and laterally, making visualization more difficult in the second and third trimesters, ultrasound remains the evidence-based first step in the diagnostic pathway.

Step-by-Step Solution

1
Identify the primary clinical syndrome from the patient's presentation.
The patient presents with right-sided abdominal pain, fever, nausea, and leukocytosis, which is highly suspicious for acute appendicitis.
Recognizing the suspected diagnosis is the first step in determining the appropriate diagnostic pathway.
2
Account for the physiological and anatomical changes of pregnancy.
The patient is 2626 weeks pregnant. The enlarging uterus displaces the appendix superiorly and laterally from its normal right lower quadrant position to the right mid-to-upper abdomen.
Anatomical changes alter the expected physical examination findings (e.g., pain location) and can make imaging visualization more challenging.
3
Select the most appropriate, safe initial imaging modality based on clinical guidelines.
Graded compression ultrasonography is chosen as the first-line test.
Ultrasonography is non-ionizing and safe for the fetus. While MRI is also safe, it is reserved as a second-line test if the ultrasound is non-diagnostic.

Key Concept

The initial imaging modality of choice for suspected acute appendicitis in a pregnant patient is graded compression ultrasonography, as it avoids exposing the fetus to ionizing radiation. MRI without contrast is used as a second-line study if ultrasonography is indeterminate.
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Topics

Ordering Imaging Studies

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