Review Question - QID 109244

A 3-day-old boy is evaluated in the neonatal intensive care unit for failure to pass meconium. The patient is otherwise doing well and feeding every 2 hours. He is urinating 8-10 times per day. The patient has had 2 episodes of vomiting that were described as green in color. He was born at 39 weeks gestation to a 38-year-old G3P3 mother. The pregnancy was uncomplicated, and the patient’s mother received routine prenatal care. She declined prenatal testing. One of the patient’s older siblings has Down syndrome. The patient's temperature is 98.2°F (36.8°C), blood pressure is 48/32 mmHg, pulse is 164/min, and respirations are 48/min. On physical exam, the patient is in no acute distress. His abdomen is firm, non-tender, and distended with hypoactive bowel sounds. A digital rectal exam fails to relieve the obstruction. An abdominal radiograph is performed and the result can be seen in Figure A. Which of the following is the most appropriate next step in management?