Visual Diagnosis: Tachypnea and Abdominal Distention in a 5-week-old Boy

A 5-week-old boy born at 35 weeks’ gestation develops acute, worsening abdominal distention and tachypnea while recovering from surgical aortic switch, ventricular septal defect (VSD) repair, and placement of a pacemaker for a history of double-outlet right ventricle, transposition of the great arteries, and congenital heart block. His postoperative course is complicated by a wound infection requiring a wound vacuum, septic shock, and bilateral chylothorax that is drained with a chest tube. He is receiving supplemental oxygen support with a nasal cannula at 2 L/min (weaned from 6 L/min of high-flow nasal cannula just 2 days earlier). His blood pressure the past few days has been stable, and he is taking furosemide. For the past 2 days the infant has become increasingly tachypneic, with a respiratory rate of 80 to 90 breaths/min. For nutrition, he is enterally fed with a high–medium chain triglyceride (MCT)–containing formula owing to the postoperative chylothorax,...