USMLE® Step 1 style questions USMLE
USMLE® Step 2 style questions USMLE
A 4-week-old girl comes to the emergency department because she has had forceful vomiting episodes. She was born full-term and weighed 2800-g (6.2-lb) at birth. These episodes started several days ago and is associated with bilious emesis. The mother notes that she has not had trouble keeping down formula until the vomiting episodes started. Her anterior fontanelle is sunken and mucous membranes appear dry. Her abdomen is tender to light palpation. Abdominal X-ray does not show signs of luminal perforation and fecal occult blood test is negative. Which of the following is the most likely diagnosis?