Abstract: Background: In clinical practice, food protein-induced proctocolitis (FPIPC) might still be misdiagnosed as neonatal necrotizing enterocolitis (NEC) for neonates with bloody stool and abdominal distension and positive portal vein gas (PVG) by abdominal ultrasound. Objective: To compare the clinical data and abdominal ultrasound examination results of NEC and FPIPC and to analyze the related factors of NEC. Design: Case-control study. Methods: Newborns with PVG positive by abdominal ultrasound were included from the inpatient settings of Children's Hospital of Chongqing Medical University from January 1, 2019 to December 31, 2019. According to the first diagnosis at discharge, they were divided into NEC group and FPIPC group. The general information, clinical manifestations and signs, the results of laboratory examination and abdominal ultrasound reports of the children were collected from the electronic medical records and the factors with statistical significance and clinical value were screened out for Logistic regression analysis. Main outcome measures: Factors associated with the diagnosis of NEC in neonates with positive PVG on abdominal ultrasound. Results: There were 68 cases in NEC group and 42 cases in FPIPC group. The gestational age, birth weight and the age and weight at the admission in the NEC group were lower than those in the FPIPC group. The percentage of abdominal distention, low reaction and reduced bowel tone, neutrophils proportion, and the percentage of elevated CRP and abnormal PCT in NEC group were higher than those in FPIPC group. The percentage of diarrhea in FPIPC group was higher than that in NEC group(P<0.05). Abdominal ultrasound examination showed the proportion of intestinal peristalsis and peritoneal effusion in NEC group was higher than that in FPIPC group (P<0.05).There was no significant difference in the age of PVG detection between the two groups. There was no significant difference in the proportion of PVG that did not disappear within 3 days after abdominal ultrasound re-examination (67 cases in NEC group and 37 cases in FPIPC group) between the two groups. Logistic regression showed that decreased abdominal bowel sounds (OR=14.7, 95%CI: 2.6~82.2, P=0.002), CRP>10 mg·L-1 (OR=24.7, 95%CI:1.4~431.7, P=0.028) and slower intestinal peristalsis(OR=26.9, 95%CI: 1.853~389.9, P=0.016) were associated with NEC. Conclusion: When abdominal ultrasound on neonates showed positive PVG, gestational age, birth weight, clinical manifestations, inflammation, abdominal ultrasound characteristics should be combined to make differentiate diagnosis. NEC should be paid attention when there were weakened abdominal bowel sounds, elevated CRP increases, and slower bowel movements by abdominal ultrasound.

Key words: Neonates, Portal vein gas, Necrotizing enterocolitis, Food protein-induced proctocolitis, Ultrasound