Necrotizing Enterocolitis: the role of ultrasound in the ...
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Necrotizing Enterocolitis: the role of
ultrasound in the assessment of bowel
viability
Ricardo Faingold, MD.
Department of Medical Imaging
The Montreal Children’s Hospital McGill University
SPR Vancouver 2017
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Disclosure
• Nothing to disclose
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Content Organization
• Introduction
• Pathophysiology,
Imaging of NEC and
Clinical aspects
• CDS Technique and
Standard Protocol
• Spectrum of Color
Doppler findings
• Case based approach
• Pearls and Pitfalls
• Conclusion
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Introduction
• NEC - Serious multifactorial GI disease of unknown etiology.
• Mainly premature infant.
• Combination of immaturity, enteral feeding, ischemia, infection, etc.
• Incidence 1 to 5 % NICU admissions.
• Pneumatosis intestinalis
• Pneumoperitoneum is only universally agreed sign - indication for surgical procedure.
• Perforation - 12-31% of neonates with NEC.
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Pathology
• Ischemic necrosis with inflammation in the mucosa and often extending through bowel wall.
• Distal ileum and prox Colon most affected.
• Any portion of intestine may be involved.
• Transmural Necrosis : excessive response of inflammatory cascade – citokines & complement.
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Bell’s Staging Criteria
– Severity of disease and guide management
– Clinical picture, laboratory and AXR
I - Suspected NEC
non specific AXR- Medical TX
II - Definite NEC –
Pneumatosis intestinalis, bowel separation, PVG etc. - Medical TX
III-Advanced / Severe –
Definite free air + findings listed in II
- Surgical. Ann Surg. 1978;187:1-7
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Abdominal Imaging
• Abdominal Radiograph (AXR): Standard modality of detection and monitoring
• US of the abdomen: Bowel assessment
– Grey-Scale
– Color Doppler Sonography (CDS)
Daneman et al. Pediatr Radiol 1978;7:70-77
Faingold et al. Radiology 2005
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Applications of Color Doppler
Sonography in NEC
• Differentiate normal from NEC (Grey-Scale)
• Assessment of bowel viability (CDS)
– Changes in gas pattern
– Gasless abdomen
– Persistent loop sign
– Slow to improve
– Worsening of clinical status
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CDS Technique & Standard Protocol Abdominal Sonography: 20 to 25 minutes
• Linear array (8-20 mHz)
4 quadrants
•bowel wall
– echotexture, thickness, peristalsis – intramural air – perfusion Color Doppler Sonography (CDS)
Color Doppler Sonography (CDS):
# of CD signals - dots or lines/cm2, optimize CDS gain and scale
•CD flow considered present when CDS signal reproducible
Other features:
• portal venous gas
• free air
• free fluid + character
• SMA/SMV + relationship
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Data Sheet
PVG- Y N
ASCITES/COLLECTION- Y N SPECIFY-
FREE AIR- Y N
BOWEL THICKNESS – MURAL AIR - PERISTALSIS - BLOOD FLOW
RUQ
RLQ
LUQ
LLQ
SMA- BLOOD FLOW (DOPPLER)
SMA/SMV RELATIONSHIP-
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CDS Technique & Standard Protocol
• NICU nurse available, neonates must be monitored. Beware of
desaturation.
• When placing transducer be gentle.
• The exam is tailored to assess bowel with CDS, however all
data is relevant. Data for each quadrant should be entered
separately
• Make sure to fill data sheet for every patient. It will help the
final report
• In case data is not available for a specific quadrant, this should
be mentioned in the report. For example, “RUQ equivocal”.
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Ultrasound
• FINDINGS according to literature:
– Free air
– Portal Venous Gas (PVG)
– Ascites and Fluid collection (Debris)
– Bowel wall thickening
– Bowel wall thinning
– Pneumatosis Intestinalis
Faingold et al. Radiology 2005
Epelman et al. Radiographics 2008
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Ultrasound
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Ultrasound
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NEC - Bowel Wall Appearance
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NEC - Bowel Wall Appearance
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Color Doppler Sonography • CDS Patterns of Mural Perfusion
– Normal
• 1-9 dots/cm2 (mean 3.78 +/- 0.20) and 0-2 lines/cm2
– increased perfusion • Rim Appearance, “Y” appearance and zebra pattern
– Absent perfusion: Sensitivity 100%, specificity 90%
• Single or multiple loops
Faingold et al. Radiology 2005
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Video-Normal Flow
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Bowel Perfusion Patterns: Increased
Y Appearance
Rim Appearance
Zebra Pattern
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Bowel Perfusion Patterns: Absent
Single Necrotic loop Multiple Necrotic Loops
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Video-Abnormal Flow
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Video-Abnormal Flow
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Case Based Approach
• cases of NEC with AXR and CDS are provided
• Clinical information is available with the
modified Bell Staging System (Pediatr Clin North Am 1986; 33:179-201)
At the end of each case comments regarding
Imaging and outcome are available.
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Case 1 -Bell stage II A
• 5 day old female
• 32 w GA
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Case 1 -Bell stage II A
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Case 1 -Bell stage II A
• AXR showed Pneumatosis and CDS
demonstrated thick walled bowel loops with
present peristalsis and hyperemic flow pattern
compatible with viable loops.
• The premature neonate did well clinically.
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Case 2 - Bell stage III A
• 1 week old male
• 35 w GA
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Case 2 - Bell stage III A
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Case 2 - Bell stage III A
• This patient did not have pneumoperitoneum, but
had a “persistent loop sign” and was
thrombocytopenic.
• CDS showed single bowel loop without flow in
RLQ and other loops were hyperemic and viable.
• Gangrenous cecum and TI were resected and baby
did well clinically.
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Case 3 -Bell Stage II B
• 2 week old female
• 33 w GA
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Case 3 -Bell Stage II B
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Case 3 -Bell Stage II B
• Although clinically well, AXR showed asymmetry of gas pattern with loop separation.
• CDS showed hyperemic bowel loops with a single segment with thinning of bowel wall and no flow in RLQ. CDS upgraded to staging to III.
• Baby deteriorated and laparotomy disclosed gangrenous bowel loop.
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Case 4 - Bell stage III B
• 6 week old female
• 24 w GA
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Case 4 - Bell stage III B
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Case 4 - Bell stage III B
• AXR showed “free air” and with dilated loops
and separation.
• CDS demonstrated multiple bowel loops with no
CDS flow, therefore non viable.
• Neonate died less then 12 hours after CDS study.
• Remember: babies with “ Free air” may have
single or multiple bowel loops with no flow. CDS
helps “ prognosticating” even though they are
Stage III.
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Case 5 – Bell Stage II B
• 30 w GA female
• 38 w corrected
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Case 5
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• 27 w GA
• 33w corrected
Case 6-Stage II B
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Case 6
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Case 6
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Case 6
• Featureless bowel
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Case 7-Stage II A
• 28 w GA male
• 2 w old
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Case 7
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Case 7 4 weeks later
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Case 7
• “The missing link?”
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Pearls and Pitfalls
• Start with large ROIs to compare bowel .
• Presence of flow in normal cases and hyperemic patterns are obvious.
• Optimize CDS settings.
• In case of increased in gas causing artefact, if there is peristalsis - bowel is viable.
• Unstable patient not compatible with CDS evaluation. However if baby is stable and desaturates, wait until oxygen saturation returns to normal and continue exam.
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Pearls
• Knowing normal CDS is imperative.
• When neonates have more advanced disease - decrease in peristalsis and more fluid filled bowel loops.
• To implement CDS protocol, limit number of radiologists and technologists involved. It is important to get enough experience and exposure
• Use the data sheet. In the report, make sure to mention
“sampled bowel loops…” It gives credibility and
acknowledges a certain limitation of technique.
• Spend a few more minutes in RLQ. Statistically, it is the
most affected quadrant. Reposition the baby with the help
of NICU nurse.
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Pitfalls • Neonates on High Frequency Ventilation are difficult to
evaluate and CDS not reliable.
• Decrease in cardiac output and use of vasopressors and
inotropes may cause difficulty in detecting CDS signals.
Optimize settings and discuss case with neonatologist.
Follow-up may be helpful.
• Increase in bowel gas, uncooperative neonates (crying for
example) limits CDS evaluation of intestinal blood flow.
See artefact below!
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Pitfalls
• A lack of standard protocol and experience will
impact in poor performance.
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Conclusions
• CDS can depict changes in bowel wall perfusion in neonates with NEC
• Viable loops show present to flow.
• Absence of perfusion indicates bowel necrosis in NEC
• CDS comprehensive technique to assess bowel viability in neonates
• CDS operator dependent and requires use of standard protocol , technique and cooperation with NICU team
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Summary
• The applications and challenges of bowel
viability assessment in NEC were discussed.
• Comprehensive description of technique and
standard protocol were presented. Hopefully,
we will obtain a more reliable and reproducible
test across different institutions.
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Thank you !