The infant was born at 31 weeks' gestational age weighing 1213 g. He required a short course of respiratory assistance, and an umbilical artery catheter was used for the first 5 days. The hospital course was complicated on day 5 by Staphylococcus aureus sepsis and osteomyelitis of the left femur, ischium, and tibia. Purulent fluid was present at the umbilical stump. An echocardiogram showed no abnormalities. Further imaging evaluation included a contrast-enhanced computed tomographic scan (Figure 2) and a magnetic resonance image of the thorax (Figure 3).