Utility of Bowel Ultrasound in Diagnosing Necrotizing Eneterocolitis in Congenital Heart Disease

Necrotizing enterocolitis (NEC) is the most common bowel disease in premature and low birth
weight neonates. NEC is defined by the loss of mucosal integrity of the bowel wall enabling
bacteria and other toxins to permeate into the bowel causing ischemia and necrosis which can
lead to bowel perforation and sepsis. NEC can result in substantial morbidity and mortality
and prolonged hospital and ICU stays.

Studies have shown that full-term neonates with congenital heart disease (CHD) are 3.7 to 6.3
times as likely to develop NEC compared with other premature neonates. The overall incidence
of CHD is up to 12-14 per 1,000 live births and the incidence of NEC in patients with severe
CHD is up to 10%. Patients with CHD have diastolic hypoperfusion causing inadequate blood
circulation which can increase their risk of developing NEC. Treatment of NEC is often
dependent on the clinical severity of the patient. Conservative treatment can be done in
early stages of suspicion of NEC, while more severe NEC requires resection of the necrotic
bowel. The current standard of care for diagnosis of NEC is based upon clinical suspicion,
laboratory values and imaging characteristics found on an abdominal radiograph. Clinicians
use the Modified Bells Staging Criteria (Appendix A) to diagnose patients with suspected NEC.
Clinical manifestations often include abdominal bloating, feeding intolerance, constipation,
emesis, ileus, and/or occult or frank blood in stool.

In the past, abdominal radiography has been scored on a standard scale that correlated with
outcomes. Duke University Medical Center developed a standardized ten-point radiographic
scale, the Duke Abdominal Assessment Scale (DAAS) and was proven to be directly proportional
to the severity of NEC on patients that underwent surgery. Abdominal radiographs are assessed
for gas pattern, bowel distention, location and features, pneumatosis (gas in bowel wall),
portal venous gas and pneumoperitoneum (free air in peritoneal cavity) to indicate the level
of suspicion of NEC . The use of abdominal radiographs is the most common assessment for
suspected NEC in infants, however, there have been recent studies done on the utility of
bowel ultrasound to aid in early diagnosis of NEC due to the ability to evaluate peristalsis,
echogenicity and thickness of bowel wall, pneumatosis and the capability of doing color
Doppler to evaluate blood perfusion. A University of Toronto study used ultrasound to assess
bowel perfusion with color Doppler in neonates and found a correlation between absence of
bowel wall perfusion and the increased severity of NEC on surgical pathology . Although there
are similar signs found between abdominal radiography and bowel ultrasound, some of the more
severe features such as, pneumoperitoneum, were found to be more sensitive on bowel
ultrasound, thus potentially leading to more definitive treatment . Currently, there is no
good study evaluating whether the use of bowel ultrasound affects clinical outcomes in
patients with CHD over the use of abdominal radiography alone.

The use bowel ultrasound has yet to be adopted in the setting of suspicion for NEC at our
institution. This is primarily due to the lack of expertise of the ultrasound technologists,
radiologists and clinicians. With literature dating back to 2005 supporting the use of bowel
ultrasound in diagnosis of severity of NEC, a high volume of CHD patients at our institution
as well as new radiologists trained in bowel ultrasound, we would like to see if a regimen
involving combined ultrasound and radiograph screening for NEC would make a difference in
clinical outcomes (morbidity, mortality, and length of stay (LOS)) compared with radiograph
screening alone.

Inclusion Criteria:

- Patients age 0-6 months with CHD

- Completed one or more cardiac surgeries for CHD

- Clinicians are suspicious for NEC and order an abdominal radiograph for screening.

Exclusion Criteria:

- Patients with isolated PDA or PFO congenital cardiac abnormalities

- Unable to ultrasound the bowel (eg. gut in silo)

- Prior heart transplant