Background Necrotizing enterocolitis (NEC) is one of the most serious conditions in newborns, affecting up to 10% of very low birth weight infants (VLBW). In the most premature population mortality rates can rise as high as 60%.

Typical findings on abdominal radiography (AR) include pnuematosis intestinalis (PI), portal vein gas (PVG) and pneumoperitoneum, but are sometimes not present even in severe cases. Abdominal ultrasound (AUS) can depict PI, PVG and pnuemoperitoneum (in some cases a head of AR), but it also provides other crucial information such as bowel wall viability (thickness or thinning) and free abdominal fluid. These additional findings are helpful in expediting diagnosis and management of NEC.

Methods and analysis The hypothesis being tested is that preforming an AUR in patients with clinical symptoms of NEC but inconclusive/normal AR will enhance detection rates, and expedite treatment in infants born at <32 weeks.

Discussion The use of AUS together with AR as an add-on test may increase the accuracy of diagnosing NEC, and precipitate treatment. Swift implementation of antibiotics and bowel rest is extremely important. To our best knowledge, our study will be the first to focus only on VLBW, who are most prone to NEC. It will also be the first multi-centre study evaluating the use of AUS as an add-on test, enabling us to recruit a significantly higher number of patients compared to published studies.

Inclusion Criteria:

• Abdominal distension
• Visible bowels loops
• Feeding intolerance (defined as emesis ≥ 2 consecutive feeds, or gastric residuals of >50% per feed in ≥ 2 consecutive feeds, bilious residuals, bilious emesis)
• Temperature instability (defined as ≥ 2 consecutive measurements)
• Frank bloody stools
• Cardiovascular instability (hypotension; defined as MAP < 30mmHg, tachycardia >160/' or bradycardia < 80/')
• Recurrent apnea
• Increase of abdominal girth > 2cm (allowing inter-observer variability of 1 cm) within 12 h
• Abdominal wall erythemia

And/or at least 2 of the below laboratory findings5:

• Thrombocytopenia < 50 x103/uL
• Leukopenia <6 x106/uL
• CRP > 10 mg/L
• PCT > 1 ng/ml
• Coagulopathy

Exclusion Criteria:

• • < 22 weeks of gestational age or > 32 weeks (estimated by ultrasound)

  • Congenital abnormalities
  • No parental consent

In this single-gate study we plan to include all consecutive preterm infants (born at <32 weeks of gestation) with suspected necrotizing enterocolitis based on the presence of at least three of the above mentioned clinical symptoms 4-7:

All de-identified data collected during the trial will be available. The study protocol will also be available. These documents will be accessible to anyone who provides a methodologically sound proposal immediately following publication with no end date.