Nutritional Status and Linear Growth at Diagnosis and Their Association with Clinical Outcomes in Paediatric Inflammatory Bowel Disease: A Multicentre Cohort Study.

Background/Objectives: Malnutrition is common in paediatric inflammatory bowel disease (IBD) and may affect growth, disease severity, and clinical outcomes. The aim of our study was to assess nutritional status and linear growth at diagnosis and during follow up and to evaluate their association with clinical outcomes in paediatric IBD. Methods: This multicentre retrospective cohort study included children diagnosed with Crohn's disease (CD) or ulcerative colitis (UC) at two paediatric IBD referral centres. Clinical, biochemical, and anthropometric data were collected at diagnosis and throughout follow-up. Underweight was defined as BMI z-score ≤ -2; growth failure (stunting) was defined as height-for-age z-score ≤ -2. Results: Among 128 children with IBD (69 CD, 59 UC; mean age: 157.2 ± 29.5 months), 23% (29/128) were underweight at diagnosis, 68% (87/128) had normal BMI, and 9% (12/128) were overweight at diagnosis. Underweight status was more frequent in the CD than UC groups (30% vs. 15%; p = 0.022). Growth failure affected 7.0% of patients at diagnosis and was observed in 5.3% of patients with available data at 36 months. Stunting was more frequent in CD than UC. Biologic therapy was more frequently initiated in underweight patients (41% vs. 17%, p = 0.06). At a mean follow-up of 29.4 months, 86% (25/29) of underweight patients achieved a normal or elevated BMI. Underweight status was not associated with an increased risk of relapse (adjusted OR 0.52, 95% CI 0.19-1.30; adjusted HR 0.60, 95% CI 0.28-1.29). Conclusions: Malnutrition is frequent at diagnosis in paediatric IBD, particularly in Crohn's disease, and is associated with increased inflammatory burden. Although most patients showed improvement in nutritional status during follow-up, baseline underweight status was not independently associated with subsequent disease relapse. These findings highlight the importance of early and longitudinal assessment of nutritional status and linear growth as integral components of paediatric IBD management.