Introduction Small bowel imaging is an important part of the diagnostic work up in Paediatric IBD both for disease classification and identification of complications. Opinion varies as to the modality and timing of small bowel imaging and MRI enteroclysis has become widely available surpassing Barium studies. The utility of Ultrasound abdomen (USS) in small bowel disease has been poorly evaluated in early onset IBD.

Aims and objectives We aimed to evaluate the adequacy of USS in detection of small bowel disease at the initial work up of early onset IBD according to the Porto Criteria. We also compared the findings on MRIE to recent small bowel USS, where available, and to historical findings on USS at presentation in a known cohort of patients with early onset Crohn’s disease.

Materials and methods Data from patients with an established diagnosis of Crohn’s disease that had MRI small bowel as part of disease reassessment during a two year period (2013–2014) was collected. Findings on MRIE were compared with USS data done at the beginning of illness or concurrently for disease location, behaviour, and presence/absence of complications.

Results 33 patients with MRI small bowel study were eligible. The median age at initial diagnosis was 11.2 years. All had USS small bowel at the time of diagnosis. The median time duration to MRIE (as part of disease reassessment) was 31 months. 14/33 patients had abnormalities on MRI small bowel that were previously found on the initial diagnostic ultrasound. 4/28 of patients who had normal initial ultrasound had MRI abnormalities either indicative of small bowel disease progression or the limitation of Ultrasound. Of the 33 patients who had MRI small bowel for disease re- evaluation, 9 patients had a preceding ultrasound within 3 months. The concurrent USS were abnormal in 6 patients and correlated with MRIE findings.

Conclusion USS small bowel in the hands of a trained paediatric radiologist is useful in detecting small bowel disease and has high sensitivity as a diagnostic tool. However MRIE supersedes USS in accurate topographic mapping, definition of disease and complications. Despite the absence of small bowel disease at diagnosis, a low threshold is required for reassessing small bowel disease in early onset Crohn’s disease.