Figure 3.

21-day-old boy (born at gestational age of 23 weeks and 2 days) with perforated necrotizing enterocolitis and radiographic pneumoperitoneum; this infant died 38 days after laparotomy. (a) An abdominal radiograph obtained 1 day before US shows a relatively gasless abdomen without pneumoperitoneum. (b) Preoperative US images show increased intestinal wall echogenicity and wall thickening, and complex ascites (asterisks). (c) Preoperative abdominal radiograph obtained 4 h after US showed no free air. (d) Pneumoperitoneum appears on abdominal radiographs obtained 4 days after US.