From the Guidelines
Necrotic bowel on bedside ultrasound is characterized by absent or significantly diminished bowel wall perfusion, increased bowel wall thickness, and decreased or absent peristalsis, as well as other specific findings that help identify this life-threatening condition. The diagnostic qualities of necrotic bowel on bedside ultrasound include:
- Absent or significantly diminished bowel wall perfusion on color Doppler
- Increased bowel wall thickness (>3mm)
- Decreased or absent peristalsis
- Pneumatosis intestinalis (air within the bowel wall), which appears as hyperechoic foci or bright spots within the bowel wall
- Portal venous gas may be visible as moving hyperechoic foci within the portal vein
- Free fluid between bowel loops often indicates perforation, while dilated, fluid-filled loops suggest obstruction that may have led to ischemia
- The bowel wall typically appears hypoechoic (darker) with loss of normal layering structure
According to the WSES-AAST guidelines 1, point of care ultrasonography can have a role in showing free fluid, abscesses or intestinal distention in the emergency department, particularly when CT scan is not available. However, it is essential to note that computed tomography and magnetic resonance imaging are the most sensitive and specific imaging tests for detecting abscesses and stenosis in IBD 1.
When performing the ultrasound, use a high-frequency linear probe for superficial assessment and a curvilinear probe for deeper structures. Apply gentle pressure to avoid causing pain and thoroughly scan all four quadrants. These findings should prompt immediate surgical consultation as bowel necrosis represents a surgical emergency requiring rapid intervention to prevent sepsis and death. The pathophysiology involves inadequate blood supply to the bowel, leading to tissue death, bacterial translocation, and eventual perforation if left untreated.
From the Research
Diagnostic Qualities of Necrotic Bowel on Bedside Ultrasound
The diagnostic qualities of necrotic bowel on bedside ultrasound include:
- Persistently dilated loops of aperistaltic bowel 2
- Increase or decrease of bowel wall thickness 2
- Intramural or portal venous gas 2, 3, 4
- Loss of bowel wall perfusion 2, 3, 5
- Free intraperitoneal gas and fluid 2
- Focal fluid collections 3
- Complex ascites 3
- Absent peristalsis 3, 4
- Pneumoperitoneum 3
- Bowel wall echogenicity 3
- Bowel wall thinning 3, 4
- Absent perfusion 3
- Bowel wall thickening 3
- Dilated bowel 3
Ultrasound Findings Associated with Surgical Management or Death
Ultrasound findings associated with surgical management or death in necrotizing enterocolitis include:
- Focal fluid collections 3
- Complex ascites 3
- Absent peristalsis 3
- Pneumoperitoneum 3
- Bowel wall echogenicity 3
- Bowel wall thinning 3
- Absent perfusion 3
- Bowel wall thickening 3
- Dilated bowel 3
Diagnostic Accuracy of Bowel Ultrasound
The diagnostic accuracy of bowel ultrasound for necrotizing enterocolitis is:
- Low sensitivity and high specificity for individual ultrasound findings 4
- Pooled sensitivities ranging from 0.27 to 0.48 and pooled specificities ranging from 0.91 to 0.99 for classic signs of NEC 4
- Low sensitivity and high specificity for bowel wall thinning and absent peristalsis 4
- Low sensitivity and high specificity for assessment of abdominal fluid 4