The pediatric trachea is elliptical at the infraglottic level, with the transverse diameter being narrowest. The endotracheal tube size formula, (age/4) + 3.5, with a cuffed tube makes more sense anatomically.
In a pregnant patient presenting with abdominal pain and suspected appendicitis, an initial ultrasound should be performed to exclude obstetric causes for abdominal pain. MRI may be a reasonable next study if it is immediately accessible and radiologists with expertise in MRI interpretation are available. Otherwise, CT should be utilized.