Case 4: Vomiting and Tachypnea in a 9-week-old Girl

Presentation

A previously healthy 9-week-old girl presents to the emergency department with vomiting and new onset of tachypnea. She was seen in the emergency department 3 days before this visit, monitored, and discharged with a diagnosis of viral gastroenteritis. Her symptoms continued, and she was again seen in the emergency department the next day. An abdominal radiograph revealed a nonobstructive bowel gas pattern. Abdominal ultrasonography was performed to assess for pyloric stenosis and was normal. She was discharged after she was able to drink an oral electrolyte solution without vomiting. She presents again with continued nonbloody, nonbilious vomiting, although her mother is also concerned because she is having abnormal breathing. A review of systems reveals poor feeding and decreased activity. A review of her growth chart shows an 800-g weight loss in 3 days. There are no sick contacts or recent travel. She was a term infant and has been healthy until now. Her parents are second cousins, but there is no family history of significant medical problems. She has recently received her 2-month vaccinations.

On physical examination she has a heart rate of 185 beats/min and a respiratory rate of 62 breaths/min. Her other vital signs are within age-appropriate limits. She had not been tachypneic on her previous visits. She appears …