Objective: Growing evidence suggests that coeliac disease (CeD) is more common in patients with inflammatory bowel disease (IBD) but diagnostic confusion remains due to overlapping histological and clinical features. Few studies have investigated this relationship in children. We aimed to assess the prevalence of CeD in our paediatric IBD cohort and define the characteristics of IBD when CeD coexists.

Methods: We conducted a retrospective study of all patients <18 years old diagnosed with IBD in Southampton Children's Hospital between January 2019 and December 2023. Patients were identified using our IBD database, and data were collected on diagnosis, endoscopy, histopathology, serology, IBD treatment and surgery using electronic patient records.

Results: 18 of the 479 children with IBD were also diagnosed with CeD (3.75%). 14 underwent duodenal biopsy on gluten, with 13 fulfilling Marsh classification 2-3. Eight children had Crohn's disease, five had ulcerative colitis and five had IBD-unclassified. 16 out of 18 demonstrated colonic disease; 11 out of 18 had pancolitis. There was no significant difference in the rate of biological therapy use between the IBD-CeD and non-coeliac groups (50% vs 68%). No patients with IBD-CeD underwent IBD surgery.

Conclusions: 1 in 25 children with IBD had coexisting CeD. Pancolitis was the most prominent IBD phenotype but a diagnosis of CeD was not associated with increased escalation to biological therapy, and no patients required surgery. These findings help to describe the paediatric IBD-coeliac phenotype and demonstrate the importance of considering IBD in children with refractory CeD and screening for CeD in children presenting with IBD.