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.