Abstract: BackgroundIntestinal ultrasound (IUS) is a non-invasive, radiation-free method with significant value in assessing intestinal inflammation. However, its application in diagnosing pediatric inflammatory bowel disease (IBD) remains limited. ObjectiveTo evaluate the diagnostic and screening efficacy of IUS and its combination with biomarker analysis in the diagnosis IBD. DesignDiagnostic accuracy study. MethodsChildren aged 2-18 years old, admitted to the Department of Gastroenterology at Children's Hospital of Fudan University with suspected IBD (presenting with recurrent abdominal pain, altered bowel habits, hematochezia, or perianal abscess) were recruited. Within one week of admission, each patient underwent both IUS and colonoscopy. The diagnostic gold standard was based on the Porto criteria for IBD diagnosis. IUS was performed by the same ultrasound physician, who had conducted over 200 cases of IUS annually for the past two years. IUS indices and biomarker levels (ESR, CRP, FC, ALB) were collected and analyzed for their diagnostic efficacy in IBD. Main outcome measuresThe diagnostic efficacy of bowel wall thickness (BWT), mesenteric fat creeping, bowel wall stratification disruption or disappearance and Limberg level. ResultsFrom March 2023 to March 2024, 582 children with suspected IBD were admitted. A total of 212 children were included in the analysis after excluding 19 children under 2 years old, 42 children who received IBD induction therapy, 98 children with organic diseases that explained their symptoms, and 211 children who refused IUS or colonoscopy. Their ages ranged from 2.3 to 16.2 years (10.0 ± 3.4 years). The IBD group included 58 children, with 45 (77.6%) cases of Crohn's disease (CD) and 13 cases of ulcerative colitis (UC). The non-IBD group consisted of 154 children primarily diagnosed with functional gastrointestinal disorders and allergic colitis.The AUC analysis showed that BWT cutoff of >3 mm ［80.4% (95%CI: 74.2-86.5)］ performed better than >2.5 mm ［71.6% (95%CI: 65.3-77.8)］ and >4 mm ［75.1% (95%CI: 68.5-81.7)］. For BWT >2.5 mm, sensitivity was 60.4% (95%CI: 52.7-68.1) and specificity was 82.8% (95%CI: 73.0-92.5). Both BWT >3 mm and Limberg Level >1 demonstrated specificity >83% and sensitivity of 77.6%. Bowel wall stratification disruption or disappearance and mesenteric fat creeping showed specificity >96%, but sensitivity was <30%. The combination of Limberg level>1 with ESR or FC demonstrated sensitivity >60% and specificity >96.8%. ConclusionFor children with suspected IBD, BWT cutoff >3 mm is suitable for the diagnosis of pediatric IBD. The combination of BWT >3 mm and Limberg level >1 is useful for early screening and accelerated endoscopic pathological diagnosis of IBD. The presence of bowel wall stratification disruption or disappearance, mesenteric fat creeping, and the combination of Limberg score >1 with ESR or FC provides significant diagnostic value for pediatric IBD.

Key words: Bowel wall thickness, Children, Inflammatory bowel disease, Noninvasive