Subclinical Respiratory Involvement in Children with Inflammatory Bowel Disease: FeNO Elevation in Active Disease

Objectives: We aimed to assess fractional exhaled nitric oxide (FeNO) and spirometry in pediatric patients with inflammatory bowel disease (IBD) and relate these parameters to disease activity, duration, and current treatment. Methods: This prospective case–control study included 161 subjects: children with newly diagnosed, active IBD (N = 55), children in clinical remission (N = 53), and healthy controls (N = 53). FeNO was measured using a chemiluminescent analyzer, and pulmonary function was assessed by spirometry. Results: FeNO was higher in patients with IBD than in controls (p = 0.025) and positively correlated with CRP (ρ = 0.22; p = 0.027). Respiratory function measured by spirometry in children with IBD was preserved. No association was found between respiratory parameters, disease activity, and duration. The correlation between FeNO and aminosalicylate treatment was of borderline significance (ρ = 0.28; p = 0.052). Conclusions: Children with IBD, although having normal pulmonary function measured by spirometry, do have increased FeNO, which is positively correlated with CRP. FeNO reflects systemic inflammation, but its role as a clinical marker of disease activity or relapse remains uncertain.