Summary of abdominal x ray and ultrasound findings in necrotizing enterocolitis. From Merrow AC Jr. Diagnostic Imaging: Pediatrics. 3rd ed. Elsevier; 2017.

1. Necrotizing enterocolitis - NEC
Imaging findings

2. 90% in the premature
with very low birth weight, < 1500g
2-3 weeks after delivery
10% in term infants
with one or more risk factors
1-3 days after delivery

3. Presentation
Signs of feeding intolerance
emesis
increased gastric residuals
bloody stool

4. Affected bowel commonly in RLQ
ascending colon
terminal ileum
but can affect any segment
from stomach to rectum

5. In the acute phase
life threatening
bowel perforation  sepsis
In the chronic phase
bowel strictures in 10-20%

6. Best imaging tools
abdominal X ray - AXR
ultrasound - US

7. AXR
nonspecific findings
suggestive findings
diagnostic findings

8. AXR
Nonspecific findings
paucity of bowel gas

9. AXR
Suggestive findings
fixed dilated bowel loops on serial AXR
– predictive of NEC
asymmetric bowel dilation
separation of bowel loops

10. AXR
Diagnostic findings
pneumatosis
portal venous gas
pneumoperitoneum

11. Pneumoperitoneum on AXR
overall increased lucency of upper abdomen
with liver less opaque than heart
football sign – free gas outlining falciform ligament
cupola sign – lucency of midline diaphragm
Riegler sign – gas outlining both sides of bowel wall

12. Pneumoperitoneum on AXR
cross table lateral decubitus view – crescentic
lucency overlying anterior hepatic margin
left lateral decubitus view – crescentic lucency
overlying right hepatic margin
peripheral triangles of lucency

13. US
Best clues
aperistaltic bowel with thick or thin wall
avascular bowel wall – suggests necrosis
Other
complex ascites, focal fluid collections
echogenic bowel wall with dirty shadowing – pneumatosis
portal venous gas, pneumoperitoneum