Review Question - QID 109254

A 4-week-old boy presents to the pediatrician for vomiting. The patient is breastfed and typically feeds for 20-30 minutes every 2 hours. One week ago, he began vomiting and regurgitating breastmilk through his nose after most feedings. His stools over the past week have also become blood-streaked. The patient does not seem to be in any distress when he passes these bloody stools. The patient surpassed his birth weight by 2 weeks of age but has fallen 1 standard deviation on the growth curve since then. His temperature is 98.6°F (37°C), blood pressure is 78/47 mmHg, pulse is 115/min, and respirations are 28/min. On physical exam, the patient is well-appearing. His face and back have the physical exam finding seen in Figure A. The patient’s abdomen is soft, non-tender, and non-distended. A digital rectal exam reveals a small amount of blood in the rectal vault. Which of the following is the most appropriate next step in management?