The nurse from the level 2 neonatal intensive care nursery calls you to evaluate a baby. The infant, born at 32 weeks' gestation, is now 1 week old and had been doing well on increasing nasogastric feedings. This afternoon, however, the nurse noted that the infant has vomited the last two feedings and seems less active. Your examination reveals a tense and distended abdomen with decreased bowel sounds. As you are evaluating the child, he has a grossly bloody stool. The plain film of his abdomen is shown. The next step in your management of this infant should include which of the following?
a) Intravenous antibiotics
b) Upper gastrointestinal series
c) Gastrointestinal surgery consultation
d) Parenteral nutrition